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1Back to top Go down   New K75 project Empty New K75 project Sun Oct 11, 2020 1:21 pm

kenrams

kenrams
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I saw this "project" K75 for sale in Craigslist and had to rescue it. It was the PO's first attempt at a custom bike build and it shows. I guess a lot of people don't realise the time or expertise required to modify and build a safe, functional bike. 
My plan is to fix the rear frame and suspension. The seat "subframe" is unworkable but it is the rear suspension that is "interesting" and will be fixed. The triple trees are standard Suzuki so steering lock will be very limited. I may just leave them on and move the tank back about an inch to see if that works. 
Here it is but it won't look like this for long as it will be my Covid project bike Wink ( in the background of the second pic is another K100 project I am working on. Lots of custom CNC parts (triple trees, rearsets etc ) I made when I had access to a great machine shop in Michigan. It has stalled a  bit due to a move to Asheville, NC)

New K75 project Img_1310

New K75 project Img_1410


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

2Back to top Go down   New K75 project Empty Re: New K75 project Sun Oct 11, 2020 2:28 pm

Suzi Q

Suzi Q
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Dunno if you're courting suggestions, but you could junk that destroyed frame and replace it with a cut and shut K100 frame, which would reduce the K's mighty wheelbase by 78mm. Add to that the further wheelbase reduction from the low offset yokes (-25mm?) and you could add a paralever back end (+37mm) and still have a super nimble bike, with great suspension. Weight distribution would be much better than the standard bike too - close to 50/50.


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

3Back to top Go down   New K75 project Empty New K75 project Sun Oct 11, 2020 4:02 pm

kenrams

kenrams
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Very interesting, Chris. I am absolutely open to suggestions. 

I liked the idea of getting the K75 as I do not need the power or size of the K100 as I am surrounded by the twisty roads of NC. I understand what you are saying but I hate the rear end of the K bikes, so a "cut and shut" won't work. Aesthetically, the exposed rear end of the frame looks to me like a crippled hyena. I am happy welding up my own frame and will make it follow the line of the tank while possibly lengthening the rear ( although I do have a spare paralever and gearbox). 

I agree with keeping the wheelbase as short as possible and that is why I am going to try the original Suzuki triple trees and maybe drop the forks in the trees to lower CofG a little too.


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

4Back to top Go down   New K75 project Empty Re: New K75 project Sun Oct 11, 2020 4:31 pm

Suzi Q

Suzi Q
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If you've already got a spare paralever.....then the Gods of K have got your destiny pinned, sorry.
The cut and shut is just underneath the tank - it just reduces the wheelbase by the 'missing' cylinder on a K75, you can still sort out the back end any way you want. Totally agree with the hyena observation. Great to hear that you're up for really setting about the frame.

The handling on this is a revelation, it's had the mods I'm on about, 200kg all up ready too ride. 1465mm wheelbase. The overall styling is just incidental - it's the geometry that's important.
New K75 project 01016


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

5Back to top Go down   New K75 project Empty Re: New K75 project Sun Oct 11, 2020 7:36 pm

kenrams

kenrams
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That sure is one interesting bike and a good reference for me. Thanks Chris. That looks like it was built by a German engineer (rather than an Italian designer Wink ). It looks like a high end top quality build. 

FYI, I just measured my bikes wheelbase - which uses the GSXR triple trees - and the wheelbase is approx 1465mm! 

I would say, however, that I am not a fan of the lines of the new rear frame on that bike. As the frame is exposed it is apparent that none of the primary or secondary angles are correct as there are no parallels. Even the angle of the bottom of the seat hump does not follow the angle of the bottom of the tank. To clean up the rear end I am going down the Retrorides route. I already have the parts. It will be something like below but with the shorter wheelbase, I think it will look better. drunken . I'll be cutting pipe and welding it up this week so will hopefully have an update next week sometime.



New K75 project 45b3e010


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

6Back to top Go down   New K75 project Empty Re: New K75 project Mon Oct 12, 2020 5:02 am

Arlina

Arlina
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Keep us updated Smile


__________________________________________________
New K75 project Eu-log10  K1100RS/LT - R1200RT - R1100RS (RIP) - Cagiva SST 350 Ala Verde - K75LT project - K75 Schurgers - K75S
    

7Back to top Go down   New K75 project Empty Sub frame build Mon Oct 12, 2020 11:52 am

kenrams

kenrams
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OK so I've removed the rear seat part and started on the new design. This will be done in multiple parts (I don't have a tube bender) as I want the front part to angle inwards to reduce the width for my comfort. Here's the progress - the tank is in place so I can follow the line of the bottom. I've inserted slugs and also moved the tank mounts back an inch. Welds just tacked for now Wink

New K75 project Img-1511


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

8Back to top Go down   New K75 project Empty Frame updates Mon Oct 19, 2020 2:39 pm

kenrams

kenrams
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Added mounting triangle for horizontal suspension fitment and also a strengthening piece across the frame.

New K75 project Img-1410


Here's the test fitting of the suspension. It's critical to get this correct as it affects everything about how it operates. The oil and air YSS shock is specially designed to work in a horizontal position

New K75 project Img-1411

Here's the seat frame being mocked up. Due to the shape I wanted I need multiple tubes, which made the task much more complicated to get everything to align correctly

New K75 project Img-1512


I fitted a seat tray for the battery and starter solenoid. You can also see the modification underway for the seat tail unit which will give the finished bike a factory feel. This also will also give me enough space to carry a tool roll and odds and sods.

New K75 project Img-1610


So here's how the stance looks now. It's coming together more or less as planned. 

New K75 project Img-1710


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

9Back to top Go down   New K75 project Empty Battery mounted Mon Oct 19, 2020 4:25 pm

kenrams

kenrams
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here you can see the placement of the Anti- Gravity battery, starter relay, and Motogadget M-unit Blue. I'm starting the wiring from scratch as the original wiring is crazy to follow - it's much simpler starting over afresh as the motogadget eliminates all the fuses and relays. I've also put in a couple of trays under the front part of the frame.

New K75 project Img-0810


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

10Back to top Go down   New K75 project Empty Re: New K75 project Tue Oct 20, 2020 9:36 pm

Tjrad

Tjrad
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Hey Ken, figured I would move our conversation over to your thread.

Looks like you are well on your way and your geometry looks pretty good! You need to add an extra horizontal brace as far back as you can on the frame before the cut under the tank though, maybe you were already planning on it.

From the guys I have spoke too.

You definitely don’t want a stiff shock back there, you have already limited the travel almost in half

You will experience some chatter at higher speeds, meaning higher than legal, one guy said no issues til 100mph.

Extra damping will help.  

I haven’t done this swap but have worked on a few k bikes and have done a mono shock conversion in the past on a Honda.  I probably can’t help much but I have done some research so if I can help let me know.

    

11Back to top Go down   New K75 project Empty Re: New K75 project Tue Oct 20, 2020 11:29 pm

kenrams

kenrams
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Hey Tjrad
Thanks for the really helpful input which, of course, raises more questions 🤨.
So the shock I have is the one supplied with the retrorides setup (link below). It is supposed to be specifically designed for the horizontal setup. Are you saying that it doesn’t work well?
https://cafe4racer.eu/en/k-retrorides/1773-bmw-k75-100-1100-1-suspension-platform-retrorides-cnc.html#/551-kit-cnc_machined_al7075_rear_shock_yss_ma_366_aluminium_custom_series

I wondered about adding a horizontal cross brace as I’ve seen a picture of this somewhere but thought that almost all the forces generated by the rear suspension where in line with the frame, so thought it was just overkill. Easy enough for me to add a cross piece as you recommend


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

12Back to top Go down   New K75 project Empty Re: New K75 project Wed Oct 21, 2020 5:16 am

Suzi Q

Suzi Q
Life time member
Life time member
That type of rear suspension linkage has been described elsewhere on this forum as a 'force multiplier', which I thought was quite illuminating. Consider torque around the swingarm front pivot pins/axis. Easy enough to estimate the weight on the rear wheel, including rider, as around 130kg. So 130kg x whatever the swingarm length is, is the torque figure. This is resisted by the suspension linkage, which bears on the bolt/suspension eye on the welded on bracket on the frame tube/gearbox stay. The distance between this bolt/suspension eye and the swingarm front pivot is much less than the swingarm length, so the force acting will much be much greater. It looks like the ratio of the two distances is around 2.5, so the radial force at the bolt/suspension eye will be around 300kg. This will not be the only force at the bolt/suspension eye though, this is because the characteristics of that linkage will also produce a force that tends to either separate, or contract the bolt/suspension eye, and the swingarm front pivot. I have no idea how big this force will be, or what direction is will be in, but it will combine with the aforementioned radial force to produce a net bigger force, that acts not quite radially on that frame tube/gearbox stay. I'd guess this is why it is important to brace that bit of tube. I'd guess too, that is would be important to keep an eye on the front swingarm pivots as you ride and use the bike, as these will now be under a much bigger load.

Have you read the thread that deals with this - it's called analysis of stock and retrorides suspension, or, as I think of it, 'Mr Spock turns his mind to custom bikes', it's great  Surprised


EDIT; as I sit here drinking my morning coffee and nosing through the threads, I see that you have indeed appraised yourself of that fantastic 'analysis' thread. I'm sure you can still build the bike, many many custom bikes pursue form as the main aim, it's quite legit, it's called art. Go for it, make it work - that's the challenge  New K75 project 112350

...just don't ever strike a pose like this guy, also on a modified K75 and soon to lose his nose and be buggered to death...
New K75 project 2Q==


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

13Back to top Go down   New K75 project Empty Re: New K75 project Wed Oct 21, 2020 11:12 am

kenrams

kenrams
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Great info, Chris. Very thought provoking and I really like the opportunity to get the brain cells working on this issue. It takes me back to a university course I took way back in the day where we designed and built model bridges ( in the days before computer simulations 🤨). We worked out stresses and strains mathematically on paper. I seem to remember that we used vectors of force to work out stresses and strains on all the bridge connections. So kind of the same process can be used with a motorcycle frame, I guess?

So my initial thought is that the weight of the rider is acting directly on where he is sitting on the frame and that scalar force is directed where exactly? I don’t think it is all on the rear wheel. Some scalar force must be directed along the frame to the bracing strut near the middle of the bike surely? Same thought process goes for the weight of the motorcycle itself, I think. I’ll need to do some further research on this  but luckily I am having dinner with a good friend who teaches and lectures on maths but also has a physics background.

I really appreciate all thoughts and feedback on this issue!

Yikes and I thought all I had to worry about was the paint color and the electrics .

Hope the weather is OK for riding in Yorkshire, mid 70’s here so of out on the GS for a ride on the gorgeous BlueRidge Parkway in NC.


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

14Back to top Go down   New K75 project Empty Re: New K75 project Wed Oct 21, 2020 11:36 am

Laitch

Laitch
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chris846 wrote:
New K75 project 2Q==
Ride that rolling mullet, Cowboy, and to blazes with the naysayers!—Yeeeehaa!


__________________________________________________
1995 K75 81,000 miles
New K75 project Usa-lo10
    

15Back to top Go down   New K75 project Empty Re: New K75 project Wed Oct 21, 2020 11:51 am

Suzi Q

Suzi Q
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Analysing forces can be as simple or as complicated as you want. Imagine yourself sat on the bike, total weight 200kg for the bike, plus your own svelte self. Now imagine a set of bathroom scales under each wheel. That's how you conclude that the upward force on each wheel is around 130kg. Now imagine no rear suspension, just the rear wheel cantilevered on an arm fixed rigidly to the frame somewhere near the swingarm pivot. The torque at the point where that arm joins the frame is 130kg multiplied by the length of the arm. Now imagine the rigid fixing of the arm replaced with a proper pivot which cannot transmit any torque. To keep the back end from falling you have to match the torque that the wheel is applying on the swingarm with an equal amount of torque in the opposite direction. You don't have to analyse the forces within the retrorides mechanism as Tjrad has done, just imagine the entire retrorides mechanism replaced with a simple strut, more or less horizontal between its two mounting points - the threaded stud on the bevel box, and the new mounting that you have welded to the frame. That strut has to supply the necessary torque - measured around the swingarm pivot, remember - so it's the tangential distance of the strut -along which the force acts- from the swingarm pivot that is important. The retrorides design keeps this distance small - it's the most striking aspect of the 'cantilever' design - and that's why the force along the 'strut' has to be so high. So there you have it; 300KG ish acting more or less horizontally -rearwards- on the threaded stud on the bevel box, and 300kg acting forwards on the new frame mounting...forces that mostly weren't there before. As Mr Spock said; it's a force multiplier.


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

16Back to top Go down   New K75 project Empty Re: New K75 project Wed Oct 21, 2020 5:35 pm

Laitch

Laitch
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chris846 wrote:...forces that mostly weren't there before. As Mr Spock said; it's a force multiplier.
Before the widespread melding of Vulcans with Earthlings, a force multiplier was defined as something that increases the effect of a force being applied, not the amount of force being applied. The redesigning of headphones and earmuffs followed.


__________________________________________________
1995 K75 81,000 miles
New K75 project Usa-lo10
    

17Back to top Go down   New K75 project Empty Re: New K75 project Wed Oct 21, 2020 6:54 pm

Tjrad

Tjrad
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The only guy I have talked to that used that shock said it was far too stiff, he is now running a shock off a ‘01 Kawasaki, not sure which model.

In regards to the discussion today I have to agree with everything said, including the idea to just do it. There is no doubt it is a force multiplier, and no doubt there is a lot of stress on the bolt in the final drive, but the amount of bikes out there without catastrophic failure makes me feel ok about it

    

18Back to top Go down   New K75 project Empty Re: New K75 project Wed Oct 21, 2020 11:46 pm

kenrams

kenrams
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Thanks guys for your positivity - I’ll go ahead as is and add a cross brace. 
Spent the day working on wiring, painting rear cowl and brackets for tail light and indicators.


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

19Back to top Go down   New K75 project Empty Re: New K75 project Thu Oct 22, 2020 4:05 am

Suzi Q

Suzi Q
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Worry is just nature's way of getting you to focus on what's important - it's a positive feeling.

I worry -sometimes a lot- about all those welded joints in that frame that I made. I look at them very closely, often.  Shocked

I'm sure even Mr Spock worries in his own way, except he probably calls it 'rational interest' or something.

Different area of the bike; aligning the rear frame rail with the tank as you have done works really well. It's the key way to make the tank look like part of the bike, rather than an insane polygon that's landed on the top tubes. But, you seem to have gone one better and used the shapely tank from the K75s and that seems to work even better. What's under the tape - more alignment?


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

20Back to top Go down   New K75 project Empty Re: New K75 project Thu Oct 22, 2020 12:41 pm

kenrams

kenrams
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Silver member
Well spotted Chris. One of the issues that I wanted to address on the tank was the scoop at the front. Some talented people have chopped the tank and relocated the fuel pump but personally, I love the monster tank and I think it is a great part of any cafe build. So I don't want to make it smaller. Instead, I am want to weld in an aluminium filler piece to take up the gap. I only have a MIG welder so I might need to find/borrow/rent a TIG welder from someone. I don't like the ABS bits from the S. The less plastic on your cafe the better as far as I am concerned. 

As far as tank alignment goes I've moved the front tank mounting back horizontally about an inch to stop the fork legs from hitting the tank. I've also added rear mounts on the new subframe. Of course, I could have got new triple trees with a greater offset to overcome that issue as a lot seem to do, but I didn't want to increase the wheelbase or trail. Also, I didn't want to increase the already large gap between the front wheel and the radiator. Here's a pic of the tank frame mods ( and a teaser of the new racing radiator I got this morning!) for anyone interested

New K75 project Img-1810



We both agree that the humpback hyena frame of a  K bike was never designed to be exposed yet it takes a lot of effort and skill to modify. Hence lots of cafe builders leave it alone. I actually did that myself in my last K75 but I added a seat cowl that aligned with the tank line instead. It was a partial success from the looks point of view. It was a sweet ride but of course, once you get the custom build you are screwed  What a Face, so when I saw the current K75 on Craigslist I had to rescue it and sell this one: 
New K75 project P7210410


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

21Back to top Go down   New K75 project Empty Re: New K75 project Thu Oct 22, 2020 1:15 pm

Suzi Q

Suzi Q
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Ooof, welding....ally welding....onto the tank sounds scary. All I know about ally welding is that it is very very different from steel, and pre-heating/heat dissipation can be critical. I know you don't like plastic bits, but you must be expecting to use more than a scraping of filler to make good your welds on the tank, so why not consider designing your own separate infill piece from fibreglass?* You could match or contrast it into your colour scheme, and I'd bet that the finished article would look smarter than something grafted onto the tank. Don't like it? bin it and make another, which you could do without decommissioning the tank or anything else meantime.

And, anyone who's ever customised a K and struggled with that ugly part of the tank would look at it and think 'wow! great idea!

....especially if you incorporated some snazzy led sidelight/indicator repeaters in there somewhere...

*great fun and you can get high as a kite  cheers


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

22Back to top Go down   New K75 project Empty Re: New K75 project Thu Oct 22, 2020 2:25 pm

Dai

Dai
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Or throw up everywhere, then have a violent migraine attack for two days


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

23Back to top Go down   New K75 project Empty Re: New K75 project Thu Oct 22, 2020 4:38 pm

kenrams

kenrams
Silver member
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Agreed, ally welding poses lots of challenges but imagine what possibilities it opens once you have that skill! My thinking was to strip the tank to bare ally like my last bike as, again, that is "proper" cafe style. However, I may decide to paint it and if I do I will just use fibreglass. 

Oooh inserts in the piece - you read my mind! Guess what works wonderfully and it is a part from a BMW car - a Z4 to be precise and it is super cool New K75 project 447221 . Here it is : 

New K75 project S-l16010


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

24Back to top Go down   New K75 project Empty Re: New K75 project Fri Oct 23, 2020 7:31 pm

kenrams

kenrams
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Motogadget inputs/outputs, switches, battery installed, brake/indicator brackets/light installed and starter relay wired up loosely and tested. Note that is not the horn I shall be fitting.

Switch on the right side is emergency ignition switch if I forget my phone (the Motogadget Blue has a proximity ignition on capability Very Happy)
New K75 project Img-1812

These are the super cool - and expensive- illuminated mini handlebar switches that I just had to use! 
New K75 project Img-1811

Battery, indicators, starter relay, rear brake, seat cowl mounts.
New K75 project Img-1814


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

25Back to top Go down   New K75 project Empty Re: New K75 project Sat Oct 24, 2020 5:06 am

Suzi Q

Suzi Q
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Moving the tank rearwards is a good solve regarding steering lock. I suspect that many builders don't bother. I know from personal experience that a set of USD forks (much thicker stanchions) and low offset yokes really does reduce steering lock to a point where the bike becomes almost unusable to manouvre. Makes me wonder about a lot of these cool-looking custom bikes that you see.... scratch

I wouldn't think that you need to consider yokes with a bigger offset at all. The OE yokes have a very high offset, and I wonder if this was BMW's way of dealing with the way that the K was always going to be a long wheelbase bike with its inline engine. The large fork offset of the K reduces trail (it's close to 100mm for the standard bike) which lightens the steering, but at the same time the 27.5' rake is fairly relaxed and angled towards the rider, maybe because the steering head has to be so far forward to clear the engine & radiator. In contrast, sports bikes (eg the suzuki that donated your forks) headed towards ever shorter wheelbases, partly achieved by steeper rake angles (probs around 25' for the donor bike) but with reduced fork offset to maintain trail and stability. Hence the low fork offsets that these bikes started to feature. I think the yokes might work well for your bike. You seem to have lowered the front by a degree or two, which has reduced the rake, so you'll have 'matching' rake and trail (ie small and large respectively). FWIW don't assume that reduced rake on it's own quickens the steering or induces instability: Tony Foale demonstrated that this isn't the case - by constructing a BMW with an adjustable rake steering head! Rake was traditionally used on motorbikes to allow primitive and poorly engineered front suspension systems to react to road surface irregularities.


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

26Back to top Go down   New K75 project Empty Re: New K75 project Sat Oct 24, 2020 4:48 pm

kenrams

kenrams
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I agree about the unfunctional "cool" looking bikes you see on youtube where the clipons are halfway down the fork legs and the rear sets are so far back that they are practically lying on the tank and all the weight is on their wrists. There is no way they can be ridden for long on any serious roads. 

Good info on rake and trail.

Just fitted the new headlight and nearly finished the modified seat cowl. Just test fitted and am pleased with the result and the paint colour (Duplicolor Ford Magnetic) of the cowl.
New K75 project Img-1815


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

27Back to top Go down   New K75 project Empty Re: New K75 project Tue Nov 03, 2020 1:54 pm

Suzi Q

Suzi Q
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Life time member
How's the project going!

You seemed to be flying ahead with things - has life/work/wife/kids got in the way - it does for me!

Radiator - just noticed you've still used the pump-to-radiator hose from a K75s or c. This has an inward offset at the top where it exits the crank cover. This is unlike the hoses fitted to every other K bike, which are straight. This is because the radiator fitted to the K75s or c is in fact narrower than every other K bike. It always strikes me as a BMW afterthought because that hose offset seems so clumsy. In your case I guess that the aftermarket radiator is for a 'standard' K, so it doesn't need the offset hose, and maybe would sit central with the frame if you used a straight, 'standard' hose?
Eye for detail huh? Just trodden the path that's all  Smile

Edit; had another look at the pic and it does look like the radiator is central, and needs a straight hose to fit properly. Removing that hose from the crank cover was the thirteenth labour of Hercules - uncompleted*

*As regards the fourteenth labour - putting the new hose back in the crank cover, they never got round to that - by that point Hercules had told them to f*ck right off.


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

28Back to top Go down   New K75 project Empty Re: New K75 project Tue Nov 03, 2020 2:24 pm

kenrams

kenrams
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Hey Chris, at the moment I am just test fitting everything but must admit I never even noticed the kink in the pipe. The rad is bigger than the old one for sure so probably fits both. I’ll probably replace the hoses with maybe silicone ones when I am doing the final build. I’m wondering about fans at the moment. Thinking of maybe a small electric one in front of the rad?

Project has stalled a little as I had a bit of an off riding my bicycle down a mountain. Broken bones severely limit the ability to do stuff! Might be a month or so before I can get back to it😤


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

29Back to top Go down   New K75 project Empty Re: New K75 project Tue Nov 03, 2020 2:35 pm

Suzi Q

Suzi Q
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Life time member
I have 2 K75 engined bikes, both ridden as hard as I can, neither has a fan. I think it helps not having the big enclosing RT fairings and the like. I fitted a coolant temperature gauge to the one that's ridden the hardest, and the temperature is never a problem. Don't think this would work in Arizona mind!
I have had a naked K100 for over thirty years, the only time the fan has ever come on was when I had a leaking coolant filler cap. Temps here are mid 20'c on a good day in midsummer (we get 2 of those every year  Cool ) 10-20'c for most of the riding season.

Ouch re. the off  New K75 project 76715


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

30Back to top Go down   New K75 project Empty Re: New K75 project Tue Nov 03, 2020 5:59 pm

kenrams

kenrams
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Silver member
Cool, I’ll nix the fan as I like the cleaner look anyway. The new radiator volume is at least 25% greater than the old so I think I have plenty of leeway. I live in the mountains and the weather is rarely excessively hot unlike in Michigan where I used to live🥵.

The down time will be an opportunity to plan an off-road epic for next Spring on the GS. Here’s the route that we might take : https://ridebdr.com/nebdr/


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

31Back to top Go down   New K75 project Empty Re: New K75 project Wed Nov 25, 2020 2:39 pm

roach374

roach374
Silver member
Silver member
@kenrams, what did you do with the ABS on the bike, just remove it completely? I'm embarking on a similar build in the near future (retrorides conversion of a K75), and wondering what to do with my ABS. Seems a shame to just chop it.

    

32Back to top Go down   New K75 project Empty Re: New K75 project Wed Nov 25, 2020 2:43 pm

roach374

roach374
Silver member
Silver member
chris846 wrote:I wouldn't think that you need to consider yokes with a bigger offset at all. The OE yokes have a very high offset...

Do you know the exact offset, by chance? I see lots of measurements online for rake and trail, but nothing for offset (or my google-foo is weak).

    

33Back to top Go down   New K75 project Empty Re: New K75 project Wed Nov 25, 2020 3:43 pm

Suzi Q

Suzi Q
Life time member
Life time member
You asked for a number, but you get an entire thread!

https://www.k100-forum.com/t13270-stock-offset-of-the-triple-tree-clamp


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

34Back to top Go down   New K75 project Empty Re: New K75 project Wed Nov 25, 2020 4:42 pm

kenrams

kenrams
Silver member
Silver member
Well that was a fun read, Chris. I wonder what the outcome finally was with the build. 

@roach374 my bike has a 2005 GSXR front end with original triple tree and Cognito moto stem and AllBalls bearings. Pretty standard stuff. So the offset is standard Suzuki - 30mm. As I previously mentioned I solved that tank clearance issue by moving the tank mounts back around 1 inch. I can always replace the triple trees if I find I have an issue with handling. It is all well theorizing in the garage but I’ll definitely take it to the track to test the handling when I get to that stage. 

Re ABS It was all off the bike when I picked up the project. The ABS system adds quite a lot of complicated wiring/electronics/weight, so I will not be fitting it back to the bike. Also it’s not compatible with the GSXR front end. I am in the middle of building the new harness now and it is amazing how much of the ABS wiring is lying on the shop floor.

Cheers


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

35Back to top Go down   New K75 project Empty Re: New K75 project Wed Nov 25, 2020 4:53 pm

roach374

roach374
Silver member
Silver member
chris846 wrote:You asked for a number, but you get an entire thread!

https://www.k100-forum.com/t13270-stock-offset-of-the-triple-tree-clamp

Thanks! Sounds like it's 56mm from that thread. Also sounds like I might want to add a mm or two, if I'm sticking USD shocks on there, to account for the beefiness and keep my steering lock where I like it.


__________________________________________________
1993 K75 standard
    

36Back to top Go down   New K75 project Empty Re: New K75 project Mon Dec 07, 2020 6:28 pm

kenrams

kenrams
Silver member
Silver member
Finally got my cask off so able to get back to work on the K75. Very Happy  

I used Solidworks to design the rearsets and CNC'd them out of 6061 a few months back and finally fitted the brake side today. To eliminate the plastic reservoir and simplify the installation of the master cylinder, I used a KTM combo which cleans up the look and is very easy to bleed (unlike the other K bike rear brakes I have bled!). In my opinion they really complement the suspension setup. 

New K75 project Img-2210


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

37Back to top Go down   New K75 project Empty Re: New K75 project Tue Dec 08, 2020 3:19 am

Suzi Q

Suzi Q
Life time member
Life time member
Not noticed those combo master cylinders before.
Mental note made   New K75 project 112350


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

38Back to top Go down   New K75 project Empty Re: New K75 project Wed Dec 09, 2020 5:15 pm

kenrams

kenrams
Silver member
Silver member
Test fit of the right rear set controls. I'm not sure about the gear lever and may remake it as it feels a tad short. It's also a bit boring. However gears all shift well, so linkage leverage is decent. I'm also wondering about the exhaust - I've simply sawn the exhaust in roughly half and will reweld the tail end a few inches back on. Not sure yet, once the exhaust tailpiece is on I make a decision.  I really want to highlight the triple sound but it has to also look right on the bike. 

New K75 project Img-2211


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

39Back to top Go down   New K75 project Empty Re: New K75 project Wed Dec 09, 2020 6:22 pm

kenrams

kenrams
Silver member
Silver member
Chopped the back of the exhaust off, test fitted it  and I think it looks pretty good but I might still try another pipe I have lying around.

New K75 project Img-2212


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

40Back to top Go down   New K75 project Empty Re: New K75 project Mon Dec 21, 2020 2:07 am

roach374

roach374
Silver member
Silver member
@kenrams wrote:@roach374 my bike has a 2005 GSXR front end with original triple tree and Cognito moto stem and AllBalls bearings. Pretty standard stuff. So the offset is standard Suzuki - 30mm.

Aren't the GSX-R forks like a lot shorter? I did a GSX-R fork swap on my Honda, so I have it sitting next to my K75 in the garage. When I measure the two, the K75 stock forks are about 10cm longer. Are you also lowering the rear somehow, with that RetroRides suspension?

Also: Where'd you get those tank knee pads? Are they stock?

    

41Back to top Go down   New K75 project Empty Camchain guide rail removal Tue Dec 22, 2020 5:09 pm

kenrams

kenrams
Silver member
Silver member
Guys, need a bit of advice. I did a compression test and have an issue on #1 cylinder which looks like a chipped valve so need to take the head off. 

So the first step is to remove the camchain tensioner and guide rails. I've got the chain tensioner and (lower) guide rail off OK. I'm struggling with getting the (upper) guide rail off. The manual simply says remove the "upper and lower E clips and remove the guide rail". Well, this sounds easy but I have been trying to do this now for a while and I can't get it off. I can get the bottom part of the guide(at the crankshaft) off easily enough. However, I cannot seem to figure out how to get the guide off at the inlet cam sprocket side. There is not enough lateral movement of the chain to allow the guide to clear the mount. I have played with the chain position to get as much slack as I can on that side but no dice.

I know that if I take the inlet cam off then everything will come off easily but when I come to put everything back I will need to install the cams first to get them aligned with the crank before installing the tensioner. Appreciate some words of wisdom, please.

Hopefully, the photo clearly shows the issue

New K75 project Img-2310


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

42Back to top Go down   New K75 project Empty Re: New K75 project Tue Dec 22, 2020 10:43 pm

roach374

roach374
Silver member
Silver member
Can't tell for sure, but from the picture it looks like there's more than enough slack to just take the chain off, at least off the crankshaft, which might give you the lateral slack you need to take the guide rail off...

    

43Back to top Go down   New K75 project Empty Re: New K75 project Tue Dec 22, 2020 11:18 pm

kenrams

kenrams
Silver member
Silver member
I tried that. There is a lot of slack once the chain tensioner guide side is removed and this can be “moved around” by turning the crank but there is not enough to actually remove it from the crank side. I also tried to remove the chain from the camshaft sprockets but this is also not possible due to the gap between the casing and the sprockets being too small. The chain will come off the top half of the sprocket but no more. 
I can only find one YouTube video on removing the head and it shows everything about the removal process for timing chain apart from this last frustrating bit.


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

44Back to top Go down   New K75 project Empty Re: New K75 project Tue Dec 22, 2020 11:32 pm

Two Wheels Better

Two Wheels Better
Moderator
Moderator
Using the appropriate timing marks in correct position, undo the screws holding the cam sprockets, let them come off under the chain, and you can get the chain off, or at least out of the way enough. Worry about the tensioner later on.


__________________________________________________

1970 R60/5, OZ '77 R75/7-R100, '85 K100'87 K75C, OZ '87 K100RS, '93 K11-K12 Big Block, '93 K1100RS, '95 R100-Mystic, '96 K1100RS, '98 K1200RS, '00 K1200RS, '02 K1200RS, '03 K1200GT, '04 R1150R'04 R1150RT, '05 K1200S, '06 K1200R, '07 K1200R, '09 K1300GT & 2013 R1200RT-Polizei  - Beemers owned still or sold.

~We all believe what we want to believe in - Rob Dickinson
    

45Back to top Go down   New K75 project Empty Re: New K75 project Tue Dec 22, 2020 11:40 pm

kenrams

kenrams
Silver member
Silver member
Cheers, I just found a BMW service manual on a British web site which basically says the same thing. Unlike the Clymer, it says to remove the sprockets first THEN the guide. I’ll give that a go tomorrow .


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

46Back to top Go down   New K75 project Empty Re: New K75 project Wed Dec 23, 2020 12:02 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
TWB has the advice that brings joy. That is how I have removed the cams(and head) on my bikes. I don't think you can get things apart without removing the sprockets first. The reassembly process assumes they have been removed if I recall.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

47Back to top Go down   New K75 project Empty Re: New K75 project Wed Dec 23, 2020 4:49 am

Suzi Q

Suzi Q
Life time member
Life time member
#3 (#4?,#5?) There was an occasion when I tried and tried and tried and tried...
..and those sprockets have got to come off.

Follow the manual carefully re. positioning the cam lobes before removing the sprockets - you don't want the cams snapping round under pressure from the valve springs. It can happen, and it's definitely an 'oh sh*t' moment if it does.

If you are careful, you can use a scraper to ease the head gasket away on separation. I have reused them with no problems - saves a few beer vouchers.

No need to get to anal about valve timing. The sprockets are identical & keyed, so no issues there. Here's the reason BMW put holes in those sprockets - do it before disassembly (don't bother removing the chain from the crank sprocket - no need) and the thing will just fall back together. Valve timing for slackers - i.e. me Very Happy

New K75 project Img_3511


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

48Back to top Go down   New K75 project Empty Re: New K75 project Wed Dec 23, 2020 10:17 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Chris, this slacker will buy you a coupla pints if we ever get to meet for that brilliant idea! cheers


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

49Back to top Go down   New K75 project Empty Re: New K75 project Thu Dec 24, 2020 3:11 am

Suzi Q

Suzi Q
Life time member
Life time member
Hmm, it's not my idea. It's commonplace on the oilheads where the 'crank' sprocket is inaccessible without removing the engine & gearbox, and the timing chain is in danger of falling down the tunnel. Not letting you off with the beer though!

Just a thought beforehand: check the valve clearances on the bad cylinder - an excessively large clearance could indicate cylinder crud trapped on the valve seat. This would affect compression. This is mentioned in BM service bulletins and was pointed out to me/us by (I think) charlie99 and was certainly the case on an engine I stripped.

Sorry charlie, just checked the thread and it was Rick G who cam up with the info about crud on the valve seats  Smile


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

50Back to top Go down   New K75 project Empty Re: New K75 project Thu Dec 24, 2020 10:36 am

kenrams

kenrams
Silver member
Silver member
As always, thanks for the great info guys. I’ll let you know what I find inside the head. I used a cheap endoscope and it looks like the valve is seated OK but has a little bit “missing”. I forgot to mention that when I took the cover off a small brass colored 10mm bolt fell out! Yep, it was one of the camshaft bolts. So who knows other joys I will encounter but I will completely strip the engine as I really know nothing about the history of this engine and also winter is just starting here🥶.

@roach374 The bike does sit a bit lower at the front and you can see that from the angle of the horizontal lines on the engine cases. This, in my opinion, really helps transform the K75 from a hefty tourer to a racy looking cafe (plus a ton of other work😥) As you might be able to see from the pictures, I have also mounted the clip ons above the trip tree which means the bike sits even lower. Mounting the bars here gives me a bit more turn lock clearance to the tank and it feels ergonomically correct for me when I sit on the bike.
I’ve not ridden this one yet, but I have modified the stance on previous bikes and I have always liked the way they feel. However, remember I am not a professional.

You also have to decide where to mount the Retrorides suspension as that will also affect the stance, as you suggest. I have not seen any exact measurement information for placement of the bracket so I just eyeballed it by tack welding the mount before final welding, to get the swing arm angle correct (in my opinion). Note also that the bracket has to be mounted maybe 3/4 inch towards the center line of the bike to make sure the  arm and suspension unit tracks parallel to the center line. This is part of the reason that you need to put the triangular bracket near the frame mount.

The real proof will come with testing of course, but that is a ways off. Rainy day here so I’m going back to work in the garage to get the head off and see what is happening to the valve train.


__________________________________________________
1981 R100 cafe- 121,000 miles
1985 K100 cafe - 55,000 miles
1987 K75C - 44,000 miles
    

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