XR100/RM80 Conversion Pit Bike Build On A Budget – Part 5

Time to start putting the big stuff back on to make this a rolling chassis… So far I really don’t have as many hours in this project as I anticipated. Although, it’s far from being over. To see what I finished in my previous article of this build, go to Part 4 Here.

First, we’ll put the rear shock and swing-arm back on…

RM80 Shock and Swing-arm

 

Then comes the front-end and wheels to make it a rolling chassis with an engine.

It is going to look ugly for a while…

Now I want to share with you some of the issues I’ve come across on this conversion build, and try to solve them so everything properly functions. First of all, the brake pedal has some interference with the kick-starter shaft. This is probably the easiest to solve, as you won’t need to make your own pedal like other builders did with the CR85 chassis. The brake pedal still operates, but you can just grind a small notch in it to make clearance for the shaft.

Brake pedal hitting kick starter shaft.

Next problem, which I’m still trying to figure out, is the airbox/intake. I want to make everything look as close to stock as possible, so I’m still using the XR100 intake boot from the carburetor to the cylinder head. The RM85 airbox outlet for the intake boot is on the wrong side of the shock, and I can’t flip the intake boot because there is no clearance as it sits. I may have to modify/chop a section of the airbox out. Right now I have a pod filter on it right now for testing purposes.

Airbox outlet on wrong side, and no clearance to flip the intake boot…

And for the part you may or may not have been waiting for…… Since I do not like the look of the out-dated RM80 body-work, I decided to go the extra mile and convert it to the newer and much better looking RM85 styling. I did research on what parts are the same and to see if anyone else has converted theirs. I found out the front fender is about the only bolt-on for the newer plastic, and I couldn’t find anyone else that had done the conversion. That’s too bad… Because you’re going to learn how! If you’re already doing the XR100 conversion, the process to convert to RM85 plastics isn’t any harder than what you’re already doing; just takes a little patience and fitting of parts.

I don’t know how many hours I spent trying to figure out what I need to do, but I think it will be well worth it. This was because the 80 vs. the 85 parts looked the exact same, so I said screw it and ordered a tank, shroud, seat, side panels, and airbox off of eBay  After setting the tank and seat on the dirt bike, there were no mounts/holes for the rear of the seat to bolt to… So I took another look at an RM85 frame, and it finally dawned on me. Doh! There’s a post on the frame under the rear of the seat where it and the side panels bolt too! Since I’ve already done a lot of modifications to the frame, I figured this would be fairly simple. On the flip side, I made yet another mistake. The last year of the RM80 was 2001, but it got upgraded side panels, as well as fenders in 2000, although the tank/shroud remained the same. I didn’t know this when I ordered a seat from an ’01 RM80, but it doesn’t fit on the 2002 and newer RM85’s, nor a 1999 and older. This is a mistake that cost me, but now I know that they don’t match.

I used some scrap steel to make this. It’s about 7 gauge material, so it’s strong enough to hold up your rear-end. I just measured the distance between the seat mounts, cut, welded, and kept grinding the post until it fit, and the plastic bar touched the frame (see pic). I’ll drill the holes after I find out exactly where it’s going to be welded onto the frame.

Rear Seat Post

That’s all for today. I just ordered the last of the plastics I need for the conversion, so the next update will be making everything fit together, and possibly the start of a custom exhaust… I’m hoping to have this bike 100% ride-able with just two more updates, so don’t forgot to come back and check soon!

-Tom Stark

2 thoughts on “XR100/RM80 Conversion Pit Bike Build On A Budget – Part 5”

  1. I have a xr100 and I’m looking to start modifying it. I enjoy reading about your project. Good luck and keep the wrenches turning.

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