Not sure if anyone can see this photo but I just wanted to share a few things I've learned while modifying my XL 350 with CRF250R suspension/wheels etc.
To swap a CRF front end onto the XL350:
Keep the CRF stem, use conversion bearings 99-3541-5 from all balls racing. You will have to cut exactly one inch from the CRF stem and weld it back together because the XL neck is so short. It's aluminum to make sure you take it to a qualified welder. This swap will look kind of goofy if you dont de-rake the frame, you could maybe also shorten the forks internally but de-raking is the way to go. The bolt patterns for vintage fenders are the same the CRF
To swap rear swingarm/wheel onto the CRF frame:
Easy, just need 2 make two equal sized aluminum spacers to go on the outside of the swingarm. I dont recall the exact dimensions but can get that upon request. The chain will run perfectly straight. I used the stock CRF rear master cylinder and had to get creative welding a bracket to hold in in place. The brake lever was a cut up and re-welded CRF lever. Foot pegs are stock Lower shock mounts have to be fabricated and welded onto the CRF swingarm if you want to keep twin shocks. Mounts are easy to make but once again youll need an AC TIG welder. Get a front sprocket from an XL250 because they were 520
I used the Clarke univeral tank #11362. Easy to mount but I did make a custom seat, not sure how well this would fit with a stock seat but it does fit the frame!
Fitting the FCR MX 37mm carb.
This is quite the chore but I was committed to doing it. Use stock CRF throttle and cables, but youll need to widen the frame. The carb physically doesnt fit between the 2 frame rails by the subframe. I cut the welds where the frame meets the backbone and welded spacers in on each side. you have to be careful because if you widen it too much the tank wont fit properly. Youll need to keep the hot start in tact. Also youll have to make your own carb spigot but can use the CRF rubber angle piece. Use a 2" Uni pod filter
stock CRF 250R jetting works almost perfect, I have AFR tuned this setup and its a tad rich, currently experimenting with smaller pilot jets. You shouldnt have any driveability concerns though.
My engine is modifed though. 127-20 Megacycle Cam degreed to proper lobe seperation, 412cc 11:1 piston, ported head, oversized valves, custom exhaust, Electrexworld CDI
Random things I came across:
CRF250 clutch cable is a direct bolt-on and works fine.
Clutch springs from a GS1150 work and will grab better (my clutch was slipping super hard)