Loss of Compression! Help!


I need help of the likely cause and the actions of rectification on the loss of compression.

Suddenly, when I rode, I found out that the sound was hollow and deep. Feeling uneasy and pulled clutch and what do you know, it dies as if there's no more fuel. Thinking it was a foul plug, I changed the plug.

But eventually it couldn't start. Then I began to realise I need not pull the De-Comp and the kickstarter could went thru.

Need help of the likely cause and rectification before my mechanic starts to :thumbsup: me?! Please...

Using stock wr4 y2k model

sounds like one of your valves are hanging open.

Bro, is it serious?

Probable cause?

3 or 4 things would cause no compression. 1) Compression release valve is not seating, 2) valves are not seating 3) broken compression ring 4) maybe a blown head gasket.

Whip the cambox cover off and turn engine over by hand. You need to check the cam timing. If the camchain has slipped or broken then there is a good chance the valves have hit the piston and bent. Hence no compression. If you go to www.thumperfaq.com there is step by step guide in the free mods to show you how to check and set the timing. If you're not sure, let your mechanic see it.


check you carb slide to see if it is broken. mine broke and a small piece was stuck in one of my valves and I had no compression. Don't know about it dying like that though. Definately check the timing.

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