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AvTech37 01-28-2013 11:52 AM

R100R fork swap and other
Apologies if this gets posted in the wrong thread.................I'm a complete newbie to ADVrider but not to bikes, specifically BMW's. I'm embarking on a new project and wonder if anyone can short circuit some of my questions...........I'm building a 'cafe racer' using a 1993 R100R as the donor bike and the initial question I have relates to my wish to install USD forks - probably from a GSXR. Now, I'm sure I've seen on one ADV thread somone has already done this...........anyone? I'm after whether or not they did anything to the rake angle?
Overall, my current thinking on the frame / running gear is either R1100 or 1150 swinging arm, USD front forks (750 GSXR?) with 17" front wheel and possibly slight change on rake via purposely made raked yolks (triple tees). In addition, I am looking to raise the engine and brace the frame. I know its completely mad but I will do it eventually. Any comments, positive or negative appreciated.
For what it's worth, I've been riding bikes since 1969 and current run a 1975 R90s, a 1993 R100R (the one to be, er, slightly modified!), a 2003 1150GS and a 2008 HP2 sport. All different and all great fun.
Thanks in anticipation.

KhaoSanMan 01-28-2013 11:58 AM

Haven't got any info on the fork swap, but I'm all ears as I may do this in the future. I have seen but cannot find a page that lists just about all the info on just about all the forks and triples out there to help you find the models with the stuff you are after. If I find it I will post it up here but it was a huge list.

For the 1150 swingarm just keep in mind that the rear-wheel will be offset to the left without modifications. You'll have to re-lace the wheel to compensate for that or find another way to account for that.

jings 01-28-2013 12:01 PM

welcome on board sound like a good prodject was thinking along the same lines with my r80r but keep getting side tracked cutting up perfectly good k100s :wink: not mine but a like it

Rucksta 01-29-2013 06:18 AM

Differences in rake angle between the beemer and a sports bike is typically 1.5 degrees.
With the engine raised you have a bit of fudge room with dropping the front end to achieve a steeper rake.

supershaft 01-29-2013 01:23 PM

I love seeing smartly modded airheads! It pains me to see so many 'cafe' bikes modified so as to have even less cornering clearance that they have to start with which isn't much. A sport bike that you can't lean over on? That's a poser. :D Anyway, BMW forks have a lot of potential ride height for a reason. The reason being cornering clearance. GSXR forks have a lot less. 17 inch wheels and low profile tires brings it down further. Paralever rear ends increase wheelbase by quite a bit limiting cornering clearance even further since the longer the wheelbase the further you have to lean the bike over to make the same curve. Wide rear tires have the same effect for the rear tire contact patch moving to the inside of the bikes center as they lean over. Raising the engine IS a step in the right direction. I would raise it and move it forward via a drive shaft spacer on the output flange. I have seen lowering the bike pretty much like you are thinking work but remember to really raise the engine or you won't be able to go very fast around corners and I would hope that is the whole point! :D Good luck!

AvTech37 01-30-2013 10:05 AM

Thanks guys for the input to date. I appreciate the concerns raised associated with the fork length and 17" front wheels, raised engine, etc hence the questions.
I am fairly sure that someone has detailed the installation of GSR forks - probably on this forum - in the past and I'm quite happy to learn from other peoples experiences!
Current thinking (to get over the lowered frame/engine due to shorter USD forks and smaller diameter front wheel is to have yolks fabricated that not only change he rake angle but are also 'dropped' thus minimising the problem.
Again, I stress that I am currently at the planning stage so no cost involved...........just a lot of time thinking, calculating and listening!

Rapid Dog 01-30-2013 12:56 PM

Look up inmate edray. He used GSXR forks. Turned out real nice.

Oh, here'tis: Retro Modern Build (Oh Oh)

He sourced some info from inmate nella .

Here's nella's bike: R100/7 build

supershaft 01-30-2013 02:05 PM


Originally Posted by Rapid Dog (Post 20611558)
Look up inmate edray. He used GSXR forks. Turned out real nice.

Oh, here'tis: Retro Modern Build (Oh Oh)

He sourced some info from inmate nella .

Here's nella's bike: R100/7 build

And then again cornering clearance isn't a concern at all for others. See that ride off stand and how that sucker sticks out on both sides? Even with minimal sag on the taller stock front forks, I don't call ride off stands ride off stands. I call them road hooks, launchers, catapults, and low orbit boosters. They make really riding impossible and just trying to very dangerous!

AvTech37 01-31-2013 09:06 AM

Thanks for that; great info'.....appreciated!

By the way, I intend to use the bike for fast road use and track days so there will be no centre stand fitted at all - ride-off or otherwise!

Intersting point but at the risk of boring my UK colleagues, track days here in the UK are increasingly becoming subject to more stringent noise limits. Stories of 1198's, Panigales and RC8's all falling foul of the noise limits - even on standard pipes- are becoming more common so I will have to plan carefully on the airhead.

Still, at the speed I work, that will be months and months in the future.

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