Decompression ticking


4 replies to this topic
  • yamahakid426

Posted December 07, 2014 - 01:54 PM

#1

Hi i have a 2000 yz426f, i just recently put a bunch of parts on my bike one of which was a front sprocket. While i was putting it on i put the bike in gear and proceeded to tighten it with a breaker bar when the engine turned over the wrong way (aka the crankshaft went clockwise instead of counter). I assumed nothing of it other than it just turned the wrong way. When i was putting all the levers back on my bike i noticed the decompression lever was really loose. I then played with it, pulling it in and kicking the bike over a few times and it returned to a stiff pull so i thought everything was good. After everything got back together (after about 2 weeks of working on it after i only had the bike for a day) i noticed a ticking noise coming from the engine that i didn't remember being there. After closer inspection i noticed that it was coming from the decompression switch on the engine. it was ticking back and forth noticeable but the engine still ran fine so i proceeded to ride it for 20 minutes thinking maybe it was the oil i put in it (yamalube 20w 50w) or the lower octane gas i put in it. but after that it was still ticking to i took it home right away. Im not a big mechanic so i don't know much about the engines but i can definitely tell that its the decompression part. I can back this up because when i touch the lever on the handlebars it vibrates a lot. If anybody could please help that would be great.



  • grayracer513

Posted December 08, 2014 - 07:15 AM

#2

Sounds like the cable is too tight.  With the engine up against compression (turn the starter until you feel the hard spot), you should have 3mm of free cable travel at the lever before the lower lever bumps up against the lifter.



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  • yamahakid426

Posted December 08, 2014 - 07:26 AM

#3

The cable isnt tight at all, actually its more loose than tight, i tried tightening it more but that didnt work. When i was looking at the decomp part of the engine more i noticed that the spring that held the lever closed was stretched and basically wasn't even working so im assuming that the valve just isnt closing all the way. im going to get a new spring and ill try that but with these bikes usually it isnt that simple but im hopeful



  • grayracer513

Posted December 08, 2014 - 07:42 AM

#4

That would be the other reason.  The shaft needs to be removed to replace the spring.  There's a bolt with a 10mm head on the side of the head just behind the decomp lever that retains the shaft.  Note that on reassembly, the bolt has a "nose" on it that engages a groove in the shaft to keep it in place while letting it turn.  If you don't make certain that the locator pin on the bolt drops into the groove in the shaft, the nose of the bolt will come up against the shaft while there are no more than two threads engaged, and tightening it will strip the hole.  Be careful to spin the bolt all the way in "by hand", and don't overtighten it.



  • yamahakid426

Posted December 10, 2014 - 07:46 PM

#5

i took the shaft out and fixed the spring and the ticking stoped and the lever doesnt move anymore. That seems to have solved the problem, thanks 







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