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Udo 06-10-2007 07:47 PM

Another R65 Dirt Bike Project
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After much reading of posts and questions to all on this forum I've finally accumulated enough parts to start the new R65 based dirt bike. Sort of a baby GS? The frame is an early 80's R65LS, forks, front wheel, caliper/rotor off a 90 Honda CR500, motor '82 R65LS, transmission '84 R100, swing arm might be a late 70's /7, but I,m not sure. The rear wheel is a /7. Handle bars are Renthal tapered and will carry late 70's BMW controls and switches. Rear shocks are 17 1/2" Progressive that were almost impossible to find.
Thought I'd share pics and description as this comes along. A pleasant surprise was to discover that the Honda and BMW share the same size steering head bearings. A 1/2" long spacer and they bolted together.
Helpful suggestions and ideas will be welcome.

Stagehand 06-10-2007 07:57 PM

sounds like a terrific start. Will you do any frame reinforcement?

Thats really convenient, about the steering head.

gonna be street legal? lights, etc?


Udo 06-10-2007 08:07 PM

Yes on the frame reinforcement. This week I'll make and weld extra brackets at the top shock mounts, and some beefing at the steering head. I think that the Acerbis style headlamps would be the easiest for a start. Last week I received an R65 fuel tank that will have to do for awhile, till I find a GS tank. Seating hasn't been figured out yet.

Stagehand 06-10-2007 08:14 PM

yeah, subframe was my next question, but it seemed early.

how bout exhaust?

Udo 06-10-2007 08:20 PM

Exhaust? Don't need no stinking exhaust. Have given it some thought. Somewhere I should have the system I took off my old R65LS when I converted it to an R80. Larger pipes. A friend knows someone down in Boulder who builds custom bike exhaust systems. I thought I'd be able to put the two together and come up with a solution.

Stagehand 06-10-2007 08:25 PM


full speed ahead! :devildog


Looking forward to its first wheelie pic.

FR700 06-10-2007 08:48 PM


Originally Posted by Udo
Somewhere I should have the system I took off my old R65LS when I converted it to an R80. Larger pipes. A friend knows someone down in Boulder who builds custom bike exhaust systems. Helpful suggestions and ideas will be welcome.

The bigger the header diameter ,the less bottom end ,all else being equal .
I'm digging the pic:thumb

Udo 06-11-2007 04:48 AM

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The bigger pipes went on the R80, the ones I have hidden somewhere are smaller, ex-R65LS, and should work on this puppy. Here's a few more pics.

Udo 06-11-2007 04:51 AM

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I think a red powder coat frame and white other will be appropriate.

Udo 06-11-2007 04:53 AM

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one more

FR700 06-11-2007 05:38 AM


Originally Posted by Udo
one more

The TR6 is sweet ,but what's the specs on the Trumpy in the background .
TLS ,non stock trees .Don't see a shaft for the points ? Don't tease us like that .

anonny 06-11-2007 05:43 AM

Love it, keep posting progress pic's. When do you hope to have it completed?

Udo 06-11-2007 05:59 AM

Don't have an ETA in mind. Next month? End of summer? I seem to get off more on the process than the completion. The project in the background is an old school Triumph scrambler. '67 T00C frame, 73 TR5T motor, Ceriani forks, 8" TLS front brakes, 52 tooth sprocket, and more. I'm setting it up to run a Boyer with a small battery.
The TR6C is a matching number, '67 unit I finished last winter. Have it licensed and insured, so it gets some real road miles. But, right now the baby GS has got me excited. The guys who work for me here at the shop all ride Jap dirt bikes and are totally freaking out. Think I'm kind of crazy doing this. I've let them test ride my R1200 GS. They can't believe that a monster looking bike like BMW builds can be so nimble on dirt. Love it.

pvangel 06-11-2007 08:10 AM

Thats exactly how I mounted mine on my 65GS with 16.5" Progressive shocks. I reinforced the frame a lot in that area. You will find that the stiffest spring rate that Progressive offers is still too soft. Good luck with the project.

Stagehand 06-11-2007 08:19 AM

Possible to make a shock mount on the swingarm that allows a higher mounting point so you can think about a greater range of shocks?

I mean, using the conventional points you've got, you have to use big long shocks to get the travel you want. If you make some triangular shock points that raise the mounts, can you then have a greater choice in which shock to use?

damn this medium. I know what I'm thinking, but cant quite get it across.

Speaking of rear ends, whats your thoughts on drive train geometry in general? gonna leave it alone?

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