Engine Seize

I'd get an athena piston from www.MIDWESTACTIONCYCLE.com an athena piston is made with beter aluminum than any other piston and is coated so it will not seize and MIDWESTACTIONCYCLE sell gaskit kits cheap to their number is 1 800 323 0078 their great to work with I've rebuilt a few motors with them :thumbsup:

check the bearings VERY closely and the valve quides etc. I would suspect some other damage :thumbsup:

Yeah Jim I checked the bearings and found them ok. No damage whatsoever. Got to get a valve spring compressor tool to check valve seals. The head had no discoloration at all and no sigh of damage but I will still pull the valves and check seals. Amazingly enough the engine still had about 1/2 a quart of oil in it when I got her home. That, I suppose, is what kept the bottom end happy.

Instead of going with a new big bore kit I ordered stock replacement piston/rings and cylinder/gaskets. I will use the old cylinder for big bore kit the next time I change oil talking to my wife!!

thanks for all the input gang. Will keep ya posted.


Just another quick thought, is there any chance that while you were riding that some dirt could of gone in to the frame were you lost the bolt from :thumbsup:......

maybe you should flush it out with oil when your ready to go just in case

Yo Steady,

Yup, I am sure that sand and dirt got in through the hole so I am flushing everything. Luckily on the WR a screen is at the base of the frame and caught most of the crap. But I will flush everything.

Thanks for the thought!


I did a similar thing with my WR a few years back. Replated cylinder, new piston & rings but all else OK.

So when it's up and running again do what I did - lockwire both of the engine drain bolts. :thumbsup:

.......Yeah, but if you dont remeber to do them up, you wont remember to lockwire them either....!??!! LOL

Hey, guess why I found this soon-to-be-5-year-old thread?

you probably scored the piston... expect to replace the sleeve and piston (big bore) Luckly, you will HOPEFULLY find that the crank which has ball bearings and the transmission will usually survive longer than the piston with no oil, so you may get lucky!

Yep, lost the frame oil plug, engine seized but I was able to start it again without any noise...I guess I was lucky. I do not know about any damage yet, but I would guess piston and cylinder.

good luck.... wow old thread!

Just thought I would update you. According to my mechanic only the cylinder and piston were somewhat scratched. Cylinder not so much it went through the nicasil, so not to worry. The piston were due for replacement anyway. Bearings was OK, and head including cams looked just fine. Seems I got away with only minor damage. Yamaha quality!

how do i time up a wr400?

Wow, this forum really needs a moderator.

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