What You'll NeedHere's the major stuff:Motor If you started like me, you didn't have any XR100 parts and started from scratch with your stock YSR50. I didn't realise just how much little stuff I'd want off the XR, so i decided to buy a motor and all the other parts seperatly. I reasise now that was the wrong way for me to go about the project. I had the oportunity to buy a late 90's XR100 complete for $750. I could have stripped all the parts I needed from it and sold the rolling chassis for probably $2-300 on ebay parted out. I still would have put several hundred dollars into rebuilding the motor, but the project could have been completed in the $700 range. Instead I bought everything off seperately and ended up spending over $1200. MotorYou want a 1992 or newer XR100 motor so that it has CDI instead of a points ignition. I would make sure it has both sidecases and that they are not cracked. Also be sure that all the internal electronics are included. The flywheel and stator plate assembly will cost you about $250 bucks new. Check the timing tower for damage as also check the timing chain. if its really loose it could mean it's been poorly maintained and it may have jumped. turn the motor over with your hand (by the flywheel) after removing spark plug and listen for the valves hitting the piston. It shouldn't. I basically went into buying a motor expecting to put in new clutch plates, piston, rings and wrist pin, new cylinder bore, timing chain and cam sproket. Don't forget a new gasket kit too. After all of that you're motor should be good to go. ExhaustThe exhaust is a custom job. You can do like i did and buy a stock exhaust, cut it up and weld it back together like you want it, or you can do like others and build one from scratch. The biggest problem i saw with building one from scratch is finding someone who can bend 1" pipe (stock exhaust pipe size). Here is a picture of one built from scratch. He had a little fun with it. I bought my exhaust from ebay. Just the stock XR100 exhaust. it looked grungy and not in the best of shape on the ebay ad, but the seller said there were no rust problems and that the pipe was in good condition, so i bought it. ended up paying $51 for it. You can get them cheaper than that, but i needed to get it soon to start cutting it up to make the new exhaust. My local motorcycle boneyard tried to sell me one for $100, so I guess i didn't do too bad. Motor MountsThe front motor mount is also a custom job. I was lucky enough to have the help of a fellow racer and mentor Dennie Spears make mine. Other than the picture, there isn't much i can tell you about the motor mount excpet you should try to get the motor as far foward as possible. The stock rear motor mounts on the YSR chassis almost bolt right into the XR motor. All you have to do is bend out your mounts on the chassis a bit (maybe 1/8") and squeeze the motor in. Chain and Counter SproketThe YSR uses a 420 chain and the XR uses a 428 chain. To convert the motor to a 420 chain all you have to do is get XR80 sprockets. The go right on. You'll also need a new chain. The existing chain from the YSR50 setup wont be long enough. Check with other people on your tracks for gearing. We were using 12:43 on the YSR50 and went up to the 15:40 with the XR motor installed. External Electrics and Throttle AssemblyI got my CDI and Coil off ebay. Seperate bids but from the same seller. They were parting out an XR100 so I got as much from the same seller as i could to combine shipping. Both are used and from a "2002 XR100". I also got the Throttle Assembly from them too. The Three items totalled $104 including shipping. Intake Manifold and CarbThe intake is tricky. The stock one will work, but it turns your carb to the riders right directly into the frame rail. This makes it very difficult to put a filter on. Even if its a foam filter. I'm getting a custom one made by a tooling shop that brings it straight back. I'm told that a Honda XL125 intake will come straight back and bolt right up, but i'm not sure. I've also been told that the ATC185 and 200s intake will work, but i know for a fact they won't. the flange and bolts on the motor side don't line up with the xr head, and i think they turn anyways. You can make your own intake if you can fabricate your own flanges and connect it with some rubber pipe, but I haven't tried it. MiscTheres more odds and ends that you'll also need. I'll try to list some of them here: |