426 compression

6 replies to this topic
  • oz426

Posted July 30, 2002 - 07:52 PM


could anyone tell me if it should be posible to turn a wr 426 engine over by hand without the de-compression lever pulled in? I have a brand new 2002 wr 426 and i noticed that with difficulty i was able to turn the engine over by hand using all my weight. I have read on another posting that you should not be able to do this unless you have lost compression. However the bike seems to run perfectly. Is this normal?

  • lfkerby

Posted July 30, 2002 - 08:00 PM


I certainly can't turn mine over by force. Before I got the hang of the starting ritual I exerted considerable force on the kick starter with absolutely no result. Jumping up and down on it didn't help either and I tip the scales at just over 200 lbs.

  • michaeltrundle

Posted July 30, 2002 - 08:53 PM


When i first got my bike I could stand on the kickstarter and she would slowly roll past compression fairly easily without putting all my weight on it.It also started and ran fine.
Now that it has about 2000 kms on it and the rings have bedded in etc etc there is no way It will turn over without the decomp.
see how it goes after a few oil changes and a few miles under its belt. it will probably come good, mine did.

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  • oz426

Posted July 30, 2002 - 09:30 PM


Thanks for the replies

  • Bamster

Posted August 04, 2002 - 05:30 PM


That's odd ,I have a 99 WR 400 and if I stand on
the kicker with all my 1 hundred and seventy pounds it will roll over slowly ,real slowly.
I can not just kick it though.I bought this bike used and has some miles on it.Runs fine. Should I do a compression test?

  • SCteck

Posted August 04, 2002 - 06:33 PM


The first time i changed my air filter, when i kicked my bike, it started to do the same thing. I found out that some sand or material lodged itself into the valve seat. I rode the bike for a few short rides and it still had the problem. Then i went out a red lined the bike on a few quick take off's. This seemed to clear up what ever was stuck in the valve.. I also heard from dealerships that the valves expand and hang open slightly on some bikes after 10 hours of riding. You might want to check your clearance.

I hope this helps.

  • freestyle111

Posted August 04, 2002 - 06:44 PM


you can make a leakdown tester for under $30.it will help you diagnose loss of compression,whether its worn rings,intake or exhaust valves out of adjustment or headgasket.there fairly simple to make it cost me $24 and a old fouled sparkplug[punched out ceramic center of plug then tapped it to accept 1\4"air compressor fitting] to make this onePosted Image


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