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Old 05-17-2014, 05:06 PM   #1
tominboise OP
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My R80G/S fork conversion to DRZ400

I completed, more or less, my fork conversion on the mongrel R80G/S I have. I picked up a set of forks complete with triple trees from ebay for $131:



I also picked up an RM 250 front wheel and axle. The RM250 wheel is interchangeable with the DRZ and uses two spacers in lieu of one spacer and one speedo drive on the DRZ. It came with a non DOT knobby which I swapped out.

Wrapped:



Unwrapped:



Axle w/ spacers ( I ended up with two axles and used the other in the assembly. I also replaced the wheel bearings and seals with new parts:



Stem bearings....



Old triples with forks



New triples with forks:



Needed about an 8mm thick spacer on the top bearing. These are machine bushings but I will machine a proper spacer at some point...



Went to the local Interstate Plastics and got a piece of drop material. UV stabilized and complete with swanky pebble finish on the outside...



Made a spacer/mount for the binnacle..



Binnacle mounted....





Rebuilt the forks with seals and bushings...needed to shorten the springs to get the ride height I wanted. Cut them 2.5" and added PVC spacers under the rebound spring. I cut these 1/4" longer so as to set the initial preload on the springs. At some point I will likely get heavier springs, but right now am experimenting with all this.







I used the stock DRZ springs for the time being and used Belray 7wt fork oil...





It sits pretty good as is. I raised the forks in the triples 1" over stock. Ride height is not too far out of kilter now...



Needed a new front brake line, from BMW master cylinder to DRZ400 caliper. It's 52" long, braided stainless line, straight M10X1.00 on one end, 20deg bend 10mm banjo on the other. Local shop made it for me for $50. Speigal wll make you the same one for about $85 delivered.





PIcked up a white DRZ fender from ebay for the front. I need to figure out how to get the extra stickers off...



Ran the wiring for the binnacle up through the frame and through the back of the binnacle.



So far, the bike rides and handles pretty good. Sag is about right. I have ordered a bigger (280mm to 320mm) front rotor and relocation bracket for caliper, since the front brakes are marginal at this point (running the stock rotor and used pads that came from ebay.

I have a long list of wish to do's on this bike, but right now, I plan on riding it and enjoying it for awhile.
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Old 05-17-2014, 05:57 PM   #2
Box'a'bits
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Well done Tom. You'll find that once the forks are properly tuned in they make a work of difference to the ride quality.

A hairdryer will shift those stickers

Have you tried the forks at full compression to make sure you have clearance?

How do the forks work with the stock tank (clearance), & also do the steering stops work?

I have a 13mm m/cylinder & the nissin 2 pot x 27mm caliper. Even with a 320mm disc the brakes are not exactly sharp (but are just acceptable). Need a different caliper solution
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Old 05-17-2014, 06:56 PM   #3
tominboise OP
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The forks clear the stock tank (they don't hit it). The forks do hit the frame braces. On my list is modding the lower triple by drilling and tapping a couple of 6mm holes in the steering stops and threading in bolts with jam nuts. The steering stops align nicely with the boss on the front of the frame.

I need to verify full compression but so far everything is cool...
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Old 05-17-2014, 07:13 PM   #4
Udo
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As you've already seen, I'm doing almost the exact same on a '81 R80G/S I'm restoring. Haven't got as far as you have with my project. I'm pleased that you have verified that this conversion works so well. Nice job. Thank you for posting.
The machine I'm building is originally from Idaho. Small world.
http://www.advrider.com/forums/showthread.php?t=976054
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Old 05-17-2014, 07:55 PM   #5
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I've been mulling this over for so long my thoughts have mold. Thanks for showing a clear, clean pictorial on how you've done yours.

Any impression concerning the ride? (Could the ride be worse than stock?) And compared to stock what was your impression of the brakes (mine are suffering with a bad disc anyway).

Thanks!
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Old 05-17-2014, 08:41 PM   #6
Box'a'bits
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As suggested by Airhead Wrangler. You can get rubber tips with bolts bonded to the underside. Cushions the impact on the braces. Cut the tip off the rubber to get a flatter surface.

I think HPN may use this system, & I know that Adventure950 did on his build

On Gus I haven't worried because I get the some effect from the Baja designs headlight clamps.
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Old 05-17-2014, 10:13 PM   #7
tominboise OP
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Quote:
Originally Posted by Box'a'bits View Post


As suggested by Airhead Wrangler. You can get rubber tips with bolts bonded to the underside. Cushions the impact on the braces. Cut the tip off the rubber to get a flatter surface.

I think HPN may use this system, & I know that Adventure950 did on his build

On Gus I haven't worried because I get the some effect from the Baja designs headlight clamps.
Great tip - thanks for posting. I'll swing by the Home Depot for a couple.
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Old 05-17-2014, 10:23 PM   #8
tominboise OP
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Quote:
Originally Posted by elmontanero View Post
I've been mulling this over for so long my thoughts have mold. Thanks for showing a clear, clean pictorial on how you've done yours.

Any impression concerning the ride? (Could the ride be worse than stock?) And compared to stock what was your impression of the brakes (mine are suffering with a bad disc anyway).

Thanks!
The previous owner of my ride had preloaded the fork springs with PVC spacers 1-1/2" long, so the front was very harsh. I haven't played with it any other then shortening the stock DRZ springs and preloading them about 1/4". And using 7 weight fork oil. There are some big bumps on cross streets near my house and I rode them pretty hard a few times without any drama. I haven't tuned the compression at all from midpoint. I also rode it today up a 16 mile twisty road to a local ski hill (asphalt). The handling was fine. It turns in quicker than before but again, no drama. I took a run down the interstate for 5 miles or so and it tracked fine, no wobble or tank slapping going on. Speeds were probably 65 - 70 (my speedo is currently at wirespokes getting rebuilt). I have a crappy Kenda 270 on the front, so tires could make a big difference.

Braking sucks, but I must note that I installed the used brake pads on the used rotor that came with my front end (I have new EBC sintered pads and a bigger rotor on the way). That said, I didn't run into anything so I'm calling it a win. It will only get better from here. I also must note that I don't know what size brake master cylinder I have on the bike.

I like the conversion. I have more photos available of various states of disassembly and will be happy to help anyone any way I can.
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tominboise screwed with this post 05-18-2014 at 07:26 AM
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Old 05-17-2014, 11:20 PM   #9
Jim Day
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Quote:
Originally Posted by tominboise View Post
Braking sucks, but I must note that I installed the used brake pads on the used rotor that came with my front end (I have new EBC sintered pads and a bigger rotor on the way). That said, I didn't run into anything so I'm calling it a win. It will only get better from here. I also must note that I don't know what size brake master cylinder I have on the bike..

Great work and pics. Right down to the preload it sounds like you did it right.

With your braking something is wrong though.

I've done three forks with three nissin calipers, with three BMW masters: a 13mm handlebar, 15mm handlebar, and 14mm undertank master, and with all of them the braking is better then it was with the original BMW brakes. The brake setup that you got with that fork should be just about ideal a 13mm handlebar master.

15mm with the oversized disc is overkill on my DRZ400SM modded R100R but my R65 mod that used the same forks disc and caliper as yours stops so nice it's fun to brake. I kid you not with it's long wheel base it's very stable and I kind of enjoy waiting to the last minute and seeing how quickly I can get it to stop.

If I had to guess I'd say that one of your pistons is stuck or you have trapped air. I'd say piston. The first one I bought had a seized piston and it was worthless. You should be able to stop that bike on a dime with the current setup even with worn pads, if not something is mechanically wrong.
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Old 05-18-2014, 12:55 AM   #10
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I think you might need a 12 mm master cilinder. They were used on R80ST's
And if you are going to ride off road a lot a 300mm rotor should be spot on for those bikes.
But they might be hard to fing for the drz set-up. I'm using a G650X front wheel,rotor and caliper with a bracket.
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Old 05-18-2014, 01:20 AM   #11
Phreaky Phil
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Warp 9 do a 320 mm rotor and adaptor at a good price
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Old 05-18-2014, 01:34 AM   #12
RJB (holland)
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I'm about to do the same modifications but special machined triple clamps will be mounted. Personally, I don't like what the DRZ clamps do to the looks of the G/S, mainly because the headlight/dashboard seems so far away and isn't following the line of the bike.

The 12mm master cilinder is also a stock part on my R80G/S and is used on some R65 en R45 models. The partnumber is 32722302369. I'm following the advice Prutser is giving and will run this cilinder together with a 300mm disc (Lucas MST310) bolted on a KTM hub.
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Old 05-18-2014, 02:28 AM   #13
Ras Thurlo
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Quote:
Originally Posted by RJB (holland) View Post
The 12mm master cilinder is also a stock part on my R80G/S and is used on some R65 en R45 models. The partnumber is 32722302369. I'm following the advice Prutser is giving and will run this cilinder together with a 300mm disc (Lucas MST310) bolted on a KTM hub.
The ktm hub works onto drz forks?
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Old 05-18-2014, 07:25 AM   #14
tominboise OP
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Quote:
Originally Posted by Jim Day View Post

If I had to guess I'd say that one of your pistons is stuck or you have trapped air. I'd say piston. The first one I bought had a seized piston and it was worthless. You should be able to stop that bike on a dime with the current setup even with worn pads, if not something is mechanically wrong.
I had this thought, too. So I believe that I will check into this a bit later on today or tonight, and post back.
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Old 05-18-2014, 10:13 AM   #15
RJB (holland)
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I'm told that a KTM hub takes the 20mm axle and fits the DRZ fork with some spacers. The other reason for my choice is that I want to mount a 300mm brakedisc and discovered that quite a number KTM models use this and the disc is not expensive. Haan Wheels will lace this new, black hub with strong spokes and Excel rim.
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