426 compression problems

9 replies to this topic
  • GreenKLX

Posted May 14, 2006 - 08:25 PM


I posted this in another thread but didn't get a response, I could use some ideas for where to start.

So, today I finally bought a YZF! I think I got a pretty sweet deal on it. It is a 2001 with a hurricane kit. The guy said I could ride it, but it was not starting. Supposedly it was running before he put it in storage 7 months ago. It doesn't build as much compression as it is supposed to. Its hard, but I can kick through the stroke without the decompression lever. I figure either piston rings or bad valves, any input?

Oh yea, I paid $800.

I will order a clymer manual tomorrow, and check the valves this week.
I know the clean the jets, fresh gas, and new plug routine, but I need help on diagnosing the compression problem. :ride:

  • unkle_george

Posted May 14, 2006 - 09:06 PM


Pull the cover off and check the valves. If they're out of spec then they're not sealing right. If the valves are way too tight take the cams out and look for wear.
Cam journal wear is pretty common if the previous owner got it hot or ran it out of oil.

- Ryan

  • GreenKLX

Posted May 15, 2006 - 08:35 PM


Thanks, I am going to check the valves tomorrow. Anyone else have any suggestions?

  • GONE1445

Posted May 15, 2006 - 09:15 PM


mine will kick through with no decomp sometimes but not all the time my uncles does it to and he has had his since new both 2001 I dunno why it does it but it only happens once in a blue moon

  • jbrooks26

Posted May 15, 2006 - 10:56 PM


Try the oil down the plug hole trick? Could be that it sat long enough to lose the oil seal on the rings in the cylinder. Just drop about 1/2 teaspoon of oil down through the plug hole and kick it through several times without the plug in there to wash the cylinder walls down with the oil. Don't use too much or you will foul the plug. This in many cases will restore the compression on a bike that has been sitting for a while, like over winter. Hope this helps.


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  • GreenKLX

Posted May 15, 2006 - 11:03 PM


Sweet tip, I'll try that tomorrow also.
Thanks :ride:

  • GreenKLX

Posted May 17, 2006 - 04:38 PM


Okay, update time.
I did the "oil in the plug hole trick," and must have used too much because I have gone through 2 plugs in like 30 minutes of kicking. The compression does seem stronger though. I have not been able to kick through the stroke in a certain point quite a few times in trying to get the :ride: started. The two plugs I pulled had oil coating the tip, so, obviously I used too much, even though I was warned. I have a third one in there, and I think it got fouled also. Is there anyway to fix my F-up and get rid of some of the oil? I really didn't think I put much more than half a teaspoon. The bike backfired twice while kicking (loud as a shotgun). Any other tips?

  • jbrooks26

Posted May 17, 2006 - 07:00 PM


Well, you could chase the oil with a little carb cleaner to thin it out and get it to burn. Once the bike is started and running it will lube the cylinder on its own again. I seem to run into this problem every time I try this trick with the same results so don't feel bad. I have been reducing the ammount of oil every time I try. I guess maybe I will try 1/4 teaspoon next time. Keep at it, you will get it going eventually.


  • GreenKLX

Posted May 17, 2006 - 07:54 PM


:lol: :eek: :eek: :banana: :busted: ITS ALIVE!!! :smirk: :lol: :usa: :lol: :lol:

Thanks for the tip Josh. I took the plug out and pushed the kicker through the stroke with my hand, and noticed the air pushing through the plug hole. I put a clean rag on top of the hole and kicked through the stroke a bunch of times (like 30) and checked the rag. Sure enough, the extra oil was getting blown out. I kept kicking until there wasn't anymore oil being blown out. I put a fresh plug in, found TDC kicked and BAM! She runs first kick! Yes, a running 426 for $800. ME SO HAPPY!
I think that I didn't kick it enough before I put the plug back in the first time. I believe that if I would have dropped in the oil, and then kicked it over like 70+ times before putting the plug back in, than it wouldn't have fouled any plugs.

Thanks again Josh, this is why I love Thumpertalk. :ride: :lol:

  • jbrooks26

Posted May 17, 2006 - 11:40 PM


No problem, glad to hear you got it running. Sounds like a steal too! :ride:

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