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1Back to top Go down   Nature of the frame on K75 Empty Nature of the frame on K75 Wed Oct 12, 2022 5:52 am

flying finn & brick

flying finn & brick
active member
active member
Good day to highly reputable forum people!

I have a running project K75 RT and I just took it to first longer drive after I bought it. The bike had motor swap 10 years ago and was left to sit for 10 years. Motor was changed because the clutch was literally ripping itself apart every 20 to 200km. Best guess being there was something off in engine-clutch-gearbox alignment. The engine that was swapped out has one of the engine's aluminum mount rebuilt. Also fairings have seen some fixing on the other side. So it has been crashed at some point.

I suspect that I might have slightly damaged frame geometry. I took one of the front engine mounts loose and it was 2 to 3 cm of the line. When I put it back I had to bend the front mounting bar to get it on spot. Should the engine mounts be perfectly lined by standard? Also on my resent ride I noticed that the bike is slightly pulling to the right. On straight and even highway I had to keep light counter steering pressure to the left. If I took my hands of the bar the bike started to tilt right.

So my question would be that are such imperfections normal on any standard? It is 3 decades old bike but should bee of decent building quality.

    

2Back to top Go down   Nature of the frame on K75 Empty Re: Nature of the frame on K75 Wed Oct 12, 2022 6:27 am

moriarti

moriarti
Life time member
Life time member
2/3 cm out of line would worry me  affraid However before scraping the frame, you can inspect the front forks for alignment, tyre condition/wear pattern/pressure 38psi. Also, steering head bearings for condition  Very Happy Very Happy


__________________________________________________
1984 k100 rs red/black VIN  0004449
    

3Back to top Go down   Nature of the frame on K75 Empty Re: Nature of the frame on K75 Wed Oct 12, 2022 7:24 am

flying finn & brick

flying finn & brick
active member
active member
moriarti wrote:2/3 cm out of line would worry me  affraid However before scraping the frame, you can inspect the front forks for alignment, tyre condition/wear pattern/pressure 38psi. Also, steering head bearings for condition  Very Happy Very Happy

Thanks for answer!

I ride brand new BT-46 tyres with proper pressures. Steering head is solid. There could be some misalignment when it comes to forks but I'm afraid that the actual problem comes from the frame. The engine mount off-set and steering abnormalities would suggest that.

I could
1. live with the imperfect frame but it doesn't feel safe when it affects the handling.

2. get some (hopefully) straight second-hand frame but the change work would be huge

3. try to straighten the frame on some frame bench. Local restrictions allow frame-straightening by bending in case of regular steel frame. However I would still be left with frame that has extra tensions in its structure. Probably not a big problem since the frame is quite sturdy. Still a 'TYÖMAA' which means a hell lot of work.

4. Scrap the bike and sell parts. I have a running bike with spare engine so I could have some money out of it. Maybe I would buy a new K75 and proceed to my original closed-loop EFI project I had in mind. 

I am considering options 3 and 4 for now. Anyway it seems quite a setback and while trying to just enjoy a hobby it still seems like enormous amount of wasted time and resources on this bike.

    

4Back to top Go down   Nature of the frame on K75 Empty Re: Nature of the frame on K75 Wed Oct 12, 2022 8:18 am

Rick G

Rick G
admin
admin
I spent many years working on bikes for a living. Many crash repairs and after a few very bad experiences with straightening frames I came to the conclusion that a bent frame was not to be fixed. Bending a frame back into shape causes more problems down the track as you have just discovered. Feed it to the scrap metal bin and put some time into a good frame.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 2004 K1200GT 1998 K1100 LT, 1986 K75 GS.
    

5Back to top Go down   Nature of the frame on K75 Empty Re: Nature of the frame on K75 Wed Oct 12, 2022 9:17 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
I had a bike totaled in a collision with an automobile and the frame was seriously bent.  I was able to purchase a used frame in good condition with a title from a bike breaker for something like $400 which included shipping 2400km from Colorado to New York State. 

Having a bare frame made it very easy to do a paint job on the whole frame as well as changing the steering head bearings. 

I would check around, frames shouldn't be that hard to find, and if you can avoid shipping costs by picking it up yourself, they can be pretty inexpensive for what you get as well.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
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
    

6Back to top Go down   Nature of the frame on K75 Empty Re: Nature of the frame on K75 Wed Oct 12, 2022 10:35 am

duck

duck
Life time member
Life time member
flying finn & brick wrote:Good day to highly reputable forum people!

Should the engine mounts be perfectly lined by standard? Also on my resent ride I noticed that the bike is slightly pulling to the right. On straight and even highway I had to keep light counter steering pressure to the left. If I took my hands of the bar the bike started to tilt right.

Yes, the frame should line up with the mounting points on the engine.

When I made a custom K75 with a motor from one K75 and a frame from another K75 everything lined up perfectly at the front of the motor, at the top of the bellhousing and at the transmission.

Many K bikes pull to the right slightly.


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

7Back to top Go down   Nature of the frame on K75 Empty Re: Nature of the frame on K75 Wed Oct 12, 2022 11:50 am

92KK 84WW Olaf

avatar
Life time member
Life time member
It should all line up perfectly but there are shims required and its possible there is an issue there. As in lack of shims, not to mention some have a damper rubber mounting.

I have not taken a K engine out but I know the shims should exactly fill the space between engine and frame, there is not a need for the bolts to pull them together. That is going to introduce a stress into the frame, thats not good.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 54,800 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

8Back to top Go down   Nature of the frame on K75 Empty Re: Nature of the frame on K75 Wed Oct 12, 2022 12:53 pm

duck

duck
Life time member
Life time member
The only frame bolt that should need any shimming is the one at the top of the bellhousing.

I put this graphic together from the BMW manual when I built my K75 Frankenbrick:

Nature of the frame on K75 At9SDXj


__________________________________________________
Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S (K1 front end)
14 Yamaha WR250R
98 Taxi Cab K1200RS
14 K1600GT
http://www.ClassicKBikes.com
    

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