Kicking past TDC/ compression concern???

13 replies to this topic
  • bob426

Posted April 07, 2006 - 10:18 PM


I just paid an arm and a leg to have my valves adjusted. Is it normal to be able to kick past top dead center (without pulling compression release lever)??? Granted it is taking a lot of effort to do this, but should it even be possible? Any help greatly appreciated. (02 YZ426)

  • Fizz

Posted April 07, 2006 - 11:59 PM


i can do it on my bike, but i´ll have to put my whole weight on the kick for a while ....

my guess that its hard to get a perfect seal from the valves and rings ...

  • obxnc

Posted April 08, 2006 - 05:55 AM


The tech could have put too big of a shim under a cap and not letting the valve close all the way. Resulting in the condition you have described..

First off, were you able to kick past TDC before???

  • bob426

Posted April 08, 2006 - 09:17 AM


Yes, I was able to kick past TDC very easily before, now it is significantly difficult to do so. Just didn't know if it should be impossible to do or not.

  • tmckeown

Posted April 08, 2006 - 10:16 AM



Exhaust cam has a notch that will open one of exhaust valves when you kick start it. When engine starts centrifugal force will pull that notch in the cam.

In newer YZ or WR there is no compression lever, it is hot start and all it does it lets more air in to the carburator.

Timo Mc

  • crashyz426

Posted April 08, 2006 - 12:40 PM


but his is an 02 426, they still had the decomp lever....

  • berudd

Posted April 08, 2006 - 04:45 PM


Well it is pertty hard to say without seeing your bike. If I sat there pushing on mine it would eventually push through. However, sometimes I would kick it and hit the compression and it damn near broke my ankle. On the other hand, I just sold the bike and I think I saw the guy that bought it just kick it right through and start it up. I hear of people doing this so yes it is possible. However, there is no way to know if yours is too easy or not. If it starts and runs fine I am guessing you are OK.

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  • DRH

Posted April 08, 2006 - 04:59 PM


Simple answer is YES. All of the Yamaha 4 strokes can do the same....Though some are a lot harder than others....

  • GONE1445

Posted April 08, 2006 - 05:27 PM


I know what you are talking about mine will do it to but usually after a little kicking and some four letter words it stops

I hate when it does it because I can't tell weather I am on the exhaust or compression stroke

oh yea I want to know how hard is it to adjust the valves if you do it your self

  • crfmatt

Posted April 08, 2006 - 07:29 PM


HMMMMM with mine I can stand on the lever and it still wont go down..and i weigh 185. :thumbsup:

  • grayracer513

Posted April 08, 2006 - 10:35 PM


Granted it is taking a lot of effort to do this, but should it even be possible?

Yes it should. Piston rings have end gaps, and cannot possibly seal completely in a static situation like that. You're forcing 375cc or so (the intake valves close after BDC) through a .2mm by .4mm (roughly) rectangular hole (the exposed ring gap), so yes, it should take a while, but it can be done.

  • bob426

Posted April 08, 2006 - 10:40 PM


Yeah, I weigh 205, and it takes all my weight and then some jumping down force to kick it through without releasing compression! I got paranoid that these guys did not do the adjustment correctly, and that I was still losing compression. I guess with a four year old bike, that just happens. I 'm sure my rings are not forming as tight a "seal"(for lack of a better word- I realize they don't actually seal anyway) as they used to either. Thanks for all the input!

  • obxnc

Posted April 09, 2006 - 06:20 PM


After reading your posts, I thought you could kick past TDC easily now when it wouldn't before. If you can stand on it and it won't budge, that is good with tons of compression and sounds like everything is working wonderfully. My 426 wouldn't budge even with stomping on it and I weigh 220.

Next thing for you to do is the exhaust cam. Just did mine today... Wonderful... No more decompression lever.. No more starting drill..

  • GONE1445

Posted April 10, 2006 - 11:10 AM


mine will kick through relativly easey sometimes my uncles does it to he has the same bike

I dunno why it only does it once in a great while but when it doesn't do it I can stand on the kicker and it won't budge and I weigh 280

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