engine mods

I just bought a 98 wr400, its a bit older, but i wanted a project. Im powdercoating the frame and rebuilding the suspension, but while i have it apart.... what can i do in the engine? Ive heard of the timing, the grey wire and the throttle stop, ive got that. What about big bore kits, does anyone sell aftermarket hop up stuff for these yet (apart from exhaust)? Any help is appreciated, also, what would YOU improve on the engine?

I would stick to "above the head" mods, like re-timimg the cams. These motors are reliable in stock form (and plenty powerful), and internal mods will shorten the life span dramatically. Just keep the valves adjusted, good oil in it, and jetted to perfection, and it will run just as strong as the day it was bought. However, if it's been ridden for almost four years, I would take the head and cylinder off, inspect the top end, and replace the rings (at least).

thanks a ton, guys.

the '98's have a weakness at the little end so any tuning will knock this out. the cases were beefed up for'00 and so was the rod.

blueprint the engine that's all. get a race shop to set your squish at .040", new rings, re time the cams to max lift at 109d on both. go to a good pipe like the white bros and then do my jetting figures. you can get VT camwheels from falicon crankshafts of clearwater, fl.

a new camchain won't hurt while you're there.


I am looking for a fixer upper like this too.

I would start by running the new 426 rod. You can bore and replate the 400 jug too a 426 spec and run a stock 426 piston, or buy a stock 426 jug and bore it to 97mm or 444cc.

Then there is the head.

I would run kmpi ss valves as they are one piece and both cheaper and better than stock. Check out there web site-


You can run the falicon adjustable sprocketas or have powroll retime/index your stock gears and weld them into place. The gears are known to slip on the cams leading to other ugliness.


I have run the big bore kit with no reliability issues and tons of torque on tap. It has to be driven to appreciate the difference.

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