Need Help! - YZF 426 - No comp after taking out plug and kicking over

3 replies to this topic
  • Gavinator

Posted August 06, 2015 - 12:36 AM


Hey guys, I/m chasing some help if at all possible. Ive got an 03 YZF 426 and I haven't had it started in a few months so after no joy kicking it over i've pulled out the plup and gave her a few kicks. The plugs back in and now there's no compression ... its as if the decomp is engaged. Could some crap have got in and stuck the exhaust valve do you think? ... Im actually selling the bike and want to make sure its all good before doing the deal ... never had this issue before ... thanks guys   

  • moto_psycho

Posted August 06, 2015 - 03:32 AM


If you think it's just the decomp, try taking the plug out, putting the bike in gear and push it about a bit. Should get oil where its needed and the motion should free things up!

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  • Baldwin

Posted August 06, 2015 - 06:17 AM


Do you have an 03 or an 02? 2002 is a YZ426 with manual decompression lever. 2003 is a YZ450 with auto decompression exhaust cam.

It sounds like maybe the decompression plunger is stuck if you in fact have a YZ426. If you have a YZ450 then this won't be the case.

  • grayracer513

Posted August 06, 2015 - 12:05 PM


That's correct; either you have a 426, or an '03, but not both.


If you have a decompression lever (one that works a lever on the right front corner of the head), be sure it has free play in the cable when released. 


Your problem is likely to be a sticking valve.  If you can't get the bike to start, pull the valve cover and rotate the engine into a position where both cams are pointing up away from the valve lifters.  Using a small flat point punch, lightly tap each lifter a few times so as to bounce the valve back against the seat.  Then recheck the compression.

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