wr400 compression problem

Hi people hope someone can help!!!

Recently found my wr400 00' model had no compression when kicked over, removed engine from bike and had it stripped down to find piston, rings and valves were well within tolerances. The engine was rebuilt with new gaskets. I then replaced the decomp lever cable as a precaution....The engine is now back in the bike but still no compression!!!!!! Please help im at my wits end!!!! Thanks guys:banghead: :worthy:

The same thing happened to me and some others.

It's like a valve sticks open for a while then shuts.

I kicked it once and it was like the decompression lever was pulled.

walked away came back later and it was fine again.

Has not ever happend again in over 4 yrs?

if it sits for too long the oil will drip off the rings and cylinder walls, causing a no compression scenario, usually kicking it over a number of times holding the auto decomp open will get enough oil back onto the rings to get it up in compression.

Sometimes, a valve will stick open and cause the same problem, just keep kicking and it should come back...

BTW could be too much tension in the decomp lever cable ????

I was working on my friends bike last night and the spark plug was loose.

Are you sure your is tight?

Another common problem is a slipped cam gear. If the top end was recently apart and then you took it for a ride and it lost power and hasn't started since then this is probably your issue. The timing marks will still be correctly alligned, but the cam lobes have moved and are not allowing sufficient compression. If you think this is your issue, do a search for it or PM me and I'll send you some links when I get back in town in a few days.

You don't have compression??....I think it could be the Timing Chain... my father has the same problem in his 2001 wrf 400.... he replace the chain and the problem was solved....

hope it helps you:thumbsup: :thumbsup:

am having same problem at moment just lost power and stopped, any advice appreciated, av still got sum compression but not half as much as wat i had before, were the hell do i start

mmm...lost power?

It may be valves or the piston rings...:smirk:


Timing chain is as slack as a bag of nackers, tensioner fully adjusted, so mi chain is due replacing thanks guys for the advice

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