1984 WR400

The WR400 model says 84.00 is max bore but this did not clean up the bore, so as this piston is bigger and the same part number we are giving it a go.

I have been supplied with a CR430 head gasket as the WR400 gasket fouls on this size piston.

Overwise the only other 'sensible' avenue was to take the barrel out to a 430 size but that brings in other complications.

why? isnt a 430 the exact same thing as a 400 just bigger bore? would work fine just boring bigger

There are noises being made that i would need a different head too or atleast modify the current one. Also i didn't want to go 430 till i have too....

Some progress atlast the barrel is cleaned up and ready to go on. Couple of poor casting areas but much better than before!



Bottom end rebuilt and tidied up

your on your way

Polished the bottom of the transfer ports in the block. My buddy who raced chainsaws art the fairs with me in speed cutting let a local engine builder polish and port a husqvarna 288 xp chainsaw. He polished were the crank rotates too.

Ladies n gentlemen we have a complete engine



Happy days

aluminum sidecover to boot!

Frame now fixed - now time to sort everything out for the powdercoaters first time I've ever had the engine built before the chassis ....but feels like progress again

for some strange reason the chassis seems easier to get done first . I always do a complete roller before the engine. when its complete it gives a boot in the a$$ to get the motor done and back in the sweet roller you just finished. it looks like you're well on your way . can't wait to see it done.

Thanks for the kind words have made a custom swing arm bolt and added a bracket for a CR brake arm too

those sure are some purdy welds

Would'nt mind seeing some more of those 250's either ?

Those noises didn't come from my direction. What I have noticed is a head off a liquid cooled dual shock 400 that has sort of a part number cast into it is a higher compression head than the 430 head. The 430 heads have 430 stamped into them. The later 400 heads appear to be 430 heads but not stamped so. Interestingly the earliest 400 engine went down because of a hole in the piston. The only hole in a piston or any defect in the top of a piston I have come across. I actually mounted that higher compression head on a 430 it was harder to start and didn't seem to run any better. I mounted a 500 head on another one and left it there.

Hey, I've got one of those 400 WR's as well.



I adapted a set of forks from a '96 Husaberg I have. Great setup. Love the disk brake! It was my uncle's bike and only has 1300 miles on it. Had the side cover corrosion issue and a large hole in the piston. I put an aluminum side cover on it and installed a new piston. It runs really well for having sat in my uncle's back yard for 25 years. It had a 15 tooth c/s sprocket on it which worked well in the desert but I spent way too much time in first gear on single track so I switched to a 13 tooth. That transformed the bike and tightened up the gearing nicely. If I were to MX the bike this is the gearing I would use. Not sure what the tooth count is on the rear sprocket but, since it still had the original Trelleborg tires that it came with, I suspect that the rear sprocket is the original.

The engine doesn't hit like a 500 so, to keep up with them, you'll need to rev it...which you should have no problems with if you're used to those 250's. I recall the days when I had an '84 250 CR and you really didn't get anywhere when trying to lug the engine. The 400 is definitely not like that. I'd say that the top end is only slightly stronger than the 250 but where the 400 really makes up the difference is in the low end and mid range. The vibration in my 400 is not enough for me to take notice so I'd call it a very smooth running engine. The transmission shifts very nicely although I've hit a couple of false neutrals recently. Granted, I cold have been a tad more deliberate with those particular shifts. You're on the right track with those heavier springs as I suspect that the shocks were sprung for a 150 lb rider originally. I'm 245 lbs in my riding gear and it's bottomed really hard quite a few times. I'm currently considering my options for the rear shocks.

Good luck with the project...and have fun!

I was referring to having to bore my 400 out to a 430 to clean the bore up. That would of meant my 400 head would of been unusable too and then I would of had to source a 430 head to use.

lucky for me we then found a 390 piston that takes the 400 out to about a 410 and allows you to run the standard head.

Here is a picture taken today. Hope you like

those are some sweet looking rides. pic looks like it's straight out of 1984.

Nice bike!!! Thanks for all that info much appreciated. And yes I agree you def cannot lug the 250s. They are only happy when they are screaming.


Go for the option springs, you will love them

itc's have a bad habit of bottoming hard if the speed of the piston is slow enough to not bring in the bottoming washers. wide dips and smooth gullys that don't hit the wheel hard.