BMW K bikes (Bricks)

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1Back to top Go down   GSXR Front end  Empty GSXR Front end Tue Jul 07, 2020 7:11 am

Tahawai

Tahawai
active member
active member
Hi Guys - New guy here and by no means a Motobike mechanic... So first stupid question, looking at a complete front end from a suzuki gsx-r 750 (k4) with brake lines tripple clamp k7 1000 calipers wheel and discs, i could pay a bit more and get a new brembo master. Any reason i shouldnt, what should i look out for and would you upgrade to the Brembo.

    

2Back to top Go down   GSXR Front end  Empty Re: GSXR Front end Tue Jul 07, 2020 9:26 am

Suzi Q

Suzi Q
Life time member
Life time member
Hello and welcome.
Issues with putting that sort of front end on a K:
The GSXR has much less fork offset than a K (which itself has quite a lot) This is the amount by which the fork legs are set forward of the steering axis, as you look at the top of the yoke. If you compare the two sets of yokes (have a look at pics of both sets of yokes on oohbay for example) you can see that the GSXR yokes are much flatter.

This isn't a massive problem as regards the steering geometry: the GSXR yokes will give more trail when installed, which will make the bike more stable (not that it needs it) Of course, more trail also means that you will have shortened the K's wheelbase, which is no bad thing at all.

The real practical issue with this sort of conversion is that, by moving the fork legs backwards with respect to the steering head, they will be much closer to the petrol tank and this can have a big restriction on steering lock.

This is compounded by the actual diameter of those big old USD fork legs - they are much thicker than the K's 42mm or so, and this will make them collide with the tank much earlier as you steer onto full lock.

There is currently a bike for sale on oohbay; a very expensive 'pro-built' item with these sort of USD/short offset forks. In one of the pics you can see just how little steering lock it seems to have.

FWIW I have done a similar conversion myself, and I ended up cutting the tank mounting brackets off the frame and moving it rearwards by 14mm. Steering lock is still limited, but the bike is useable. I do wonder if that's the case for many of these specials that you see?

Try it and see, is my advice. This is just a heads up.

Edit: looking for a few explanatory pics. Here's a USD-forked special, but note how the builders have used a custom set of yokes that seem to keep the K's original large fork offset - this bike will go round corners!
GSXR Front end  Top_yo10
The builders are called Dixer parts, and I hope they appreciate why I have posted this picture, and don't get too concerned about copyright.


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Sometimes I'm not really Suzi Quatro.
    

3Back to top Go down   GSXR Front end  Empty Re: GSXR Front end Tue Jul 07, 2020 4:55 pm

Tahawai

Tahawai
active member
active member
Thanks Chris, that's hugely appreciated.

    

4Back to top Go down   GSXR Front end  Empty Re: GSXR Front end Tue Jul 07, 2020 7:27 pm

Tahawai

Tahawai
active member
active member
What is the most common used front end in cafe racer conversions or are most cafe racer builds using the old forks?

    

5Back to top Go down   GSXR Front end  Empty Re: GSXR Front end Tue Jul 07, 2020 7:52 pm

Two Wheels Better

Two Wheels Better
Moderator
Moderator
Tahawai wrote:What is the most common used front end in cafe racer conversions or are most cafe racer builds using the old forks?
Check out the forum's "Kustom K's" thread and peruse the various articles there - I don't know if anyone's done a survey to determine the most common on any of these K builds. For ease of use and to get later (K12/R1150) wheels and brakes up there I used the Marzocchi forks from a K1100RS on my Big Block K12-engined bike.


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1970 R60/5, '77 R75/7-R100, '85 K100'87 K75C, '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-P & 2022 S1000XR



"We take our bearings, daily, from others. To be sane is, to a great extent, to be sociable."

~John Updike.
    

6Back to top Go down   GSXR Front end  Empty Re: GSXR Front end Wed Jul 08, 2020 3:54 am

Suzi Q

Suzi Q
Life time member
Life time member
There's no rule book!

I think that sometimes these things are built for the styling more than anything else - I see far more 'cafe racers' on the internet or at bike shows than I see on the roads. I have a suspicion that some of them might not get ridden an awful lot.....

According to the bits I've seen on the internet, and build threads on this forum, I'd say that GSXR forks seem popular. My guess though is that's probs cos' they are in plentiful supply - no other reason. That and 'Gixer Forks' sounds like a he-man upgrade. Cafe racers, or special builds generally are after all supposed to be an improvement on the OE bike, maybe even a statement that the owner is such a hero that a stock bike just couldn't cut his mustard!

Seriously though, I think the better quality/pro-built bikes are more of an art form than anything, and very good art at that. The presence of expensive, albeit unnecessary or unusable components is integral to that art.

The way that art works is to inspire more mundane activities further down the line, and to legitimise or validate departures from the norm. That is where development takes place, and if it's good development, then it becomes advancement. So don't try and replicate those glossy special builds unless you're an unoriginal wannabee artist with an unjustifiably oversize budget, and you'd be happy with a scared-of-the-rain 'bike' (knobbly tyres anyone?). 

How about looking for a set of USDs (if that's what you're after) and yokes with more fork offset? Anything can be made to fit, but you'd probably need some machine shop work, and the knowledge & budget to go down this route. If you'd be happier in halford's three spanner territory, then there's a few members of this forum who really like the K1100 fork conversion which AFAIK is pretty much bolt-on if you include wheels, discs and calipers in the list. A Brembo front brake master cylinder from any F800 variant would match those calipers, and allow you to lose the OE switchgear if that suits.

Build your own thing!


__________________________________________________
Sometimes I'm not really Suzi Quatro.
    

7Back to top Go down   GSXR Front end  Empty Re: GSXR Front end Wed Jul 08, 2020 6:05 pm

stanthomas

stanthomas
Silver member
Silver member
Could go proper custom:

GSXR Front end  Elf-honda-1

That would impress me Laughing And go work really well with the low, long K motor.


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K100RS 16V '91
    

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