99 wr400 lost compression, now wont start at all

this is the story. about a week ago i was riding with some friends and the bike was running great. came out next day about to go riding again and it lost alot of compression. i figured i would try to start it, so i did and it ran ok. rode it around a little and it was fine. went for a ride yesterday and it started first kick like always when it was cold. then it started not wanting to start at all unless i bump started it. then we all stopped to take a break and my bike wouldent start at all tried bump starting it, nothing. ended up having to get towed out of the woods by a 4 wheeler. :) anybody know what could be wrong or has anybody else had this happen to them? any help would be greatly apreciated. thanks

When is the last time you checked valves? Sounds like too tight intake valve to me.

When a bike looses compression, that's a bad thing. Continuing to ride even when you know something major is wrong (like low compression) is asking for large repair bills and substantial engine damage.


i just checked the valves a couple weeks ago and they all were in spec. could the head being a little loose cause it to loose compression but still run for a while? before this problem it ran great started first kick hot or cold.

I bought a friend’s 1998 WR400 because of the same problem. He said that it was running fine one day and then nothing. I checked the lash and it was good so I pulled the cylinder and piston. The second ring was stuck in the ring land causing massive blow by and no compression. Since it was torn apart I decided to replace the piston, rings, and gaskets. It now runs like new. Well new to me at least.

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