High Compression issues


3 replies to this topic
  • ak907rider

Posted February 12, 2013 - 11:54 PM

#1

I just picked up a 2002 yz 426 and I can't get the thing to run. The compression is so high on it I can literally jump on the kicker and it wont kick. ive used the decomp lever and done too dead center and tried choke on and off as well as not touching the throttle. Just put a new spark plug in as well just to eliminate any doubts. It's inside at 70 degrees too so I know it's not too cold. I've tried all the tricks on here and researched all I can on it. I've got it to backfire a few times and start for about 5 seconds 1 time but other than that the compression is too high for it to be easily kicked over. And no I'm not sure if it has high compression pistons in it but if it did they wouldn't be that hard to kick over would they? I haven't torn it apart just yet wanting to make sure there wasn't something I was overlooking of maybe could be a problem somewhere else. I want it to run first before i go through a hot cam auto decompression in it to try and have it possibly still not work. And yes the fuel has been turned on and I've tried starter fluid. Any thoughts would be greatly appreciated. Thanks

Edited by ak907rider, February 12, 2013 - 11:59 PM.


  • DC_Excitement

Posted February 13, 2013 - 04:32 AM

#2

you have to be shure your using the decompression correctly, there is a procedure for it.

[color="#222222"]http://www.yamaha-mo...troke_vid_a.mpg[/color]

[color="#222222"]http://www.yamaha-mo...troke_vid_b.mpg[/color]

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  • grayracer513

Posted February 13, 2013 - 08:08 AM

#3

A normal, healthy, stock 426 (which has 12.5:1 compression, BTW) will be virtually impossible to kick through the complete compression stroke, and repeated attempts to do so may actually break something.

Follow the advice in the videos posted, especially regarding how far the starter is to be moved past the point where compression is felt.

  • ak907rider

Posted February 16, 2013 - 12:22 AM

#4

Just wanted to say thank you for the info. I wasn't understanding it until I really saw the video and after 30kicks it runs. Thank you guys. Will be keeping up on here.





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