Die's on Decel - Valves, Decomp lever, Carb, or worse?

10 replies to this topic
  • Sj1

Posted February 18, 2012 - 05:29 PM


2001 WR 426

So, recently I did an oil change and like a dumb*ss I forgot to tighten the bolt on the line at the bottom of the engine below the oil filter. I drain that one to get a little more dirty oil out, but in this case, I forgot to tighten it up so it was only snug fit in place and produced a pretty aggressive leak.

Unfortunately I found this after a 10 mi surface street ride to work in which I hit some high rpms. When I got home, I drained the oil and there was still a bunch in there that drained out, so thats good. If I had to guess, at least 1.25qts came out.

Thinking that all I need to do was change the oil again, I refilled it with 1.6l of new oil and verified the dip stick at the high mark after warming it up. In a stroke of sheer brilliance, I also adjusted the fuel screw a little like 1/4 of a turn as it backfired on decel after high RPM's few days ago.

The next day, I took it for a ride and it died on deceleration after running at higher rpms for a quick spurt. :bonk: The kick start kick felt a little loose after this, so after some reading I decided to check the valve clearance. The cylinder compression seems ok because at TDC I can stand on the kick starter for about 30-45 seconds before it starts to slowly drop. (i weigh about 200lbs)

Also, if I press the decomp lever it didnt always decomp and it would be like kicking a rock every now and then, but not consistantly. Sometimes it works sometimes it doesnt. Seemed like i would have to kick further down than ussual on the decomp for it to allow me to kick it over to start.

Valve situtation:

Here are the original clearances:


Left: .18

Right: .20

Spec = .20-.25 So they were tight.


Left: .10

Middle: .10


Spec = .10-.15, again all tight.

Shims before/after:


Left: 1.84/1.75 (1.84+.18-.25 = 1.77 rounded to 1.75)

Right: 1.84/1.8 (1.84+.20-.25 = 1.79 rounded to 1.8)

Equation: 1.86+.10-.15 = 1.81 rounded to 1.8

Intake: Left:1.86/1.80 (1.86+.10-.15 = 1.81 rounded to 1.80)

Middle: 1.88/1.85 (1.88+.10-.15 = 1.83 rounded to 1.85)

Right:.1.86/1.80 (1.86+.10-.15 =1.81 rounded to 1.80)

Clearances after changing the Shims:


Left: .23

Right: .23

Spec = .20-.25 So they are withing spec now.


Left: .13

Middle: .10 (.13 wouldnt fit but .10 would, so I'm thinking its ~.11 or .12) Still a little tight, but I didnt have the patience to take everything back apart and go back to the store for another shim)


Spec: .10-.15 So pretty good, but the middle is still slightly on the tight side.

Everything went back together with no issues.

Took it around the block for a ride and I'm still having the same issue dieing on decel after winding it out a little bit.
I've fiddled around with the fuel screw, and at idle I can blip the throttle all day with no issues, so I dont feel like that is the issue. Seems like it's running healthy, but then under load on decel it dies out. Kind of sputters and then when I grab the clutch it dies. Also, the issue with the decomp sporatically working persists.

So, what's next? Is it possible that a valve got stuck? Carborator gunked up due to the f'd up oil change? Something else due to the oil leak/ oil change mistake? MIddle intake shim is still too tight? Carb idle/fuel screw issue?

Should I take it to the stealership for a diagnosis?

Any suggestions or thoughts are appreciated.


Edited by Sj1, February 18, 2012 - 05:32 PM.

  • MANIAC998

Posted February 19, 2012 - 06:34 AM


Just a thought, pull the sparkplug and tell us what it looks like. I'm wondering if oil is getting past the rings on decel and basically fouling up the plug. Maniac

  • Sj1

Posted February 19, 2012 - 09:01 AM


I checked it after before doing the valve check and it seemed to be normal. A little black residue around the edge with a clean whitish electrode. I'm tied up today, but I'll pull it again tomorrow. I'm going to blow some air into the spark plug hole to see if I can hear it leak out the exhause or intake box with the crank at TDC.

While doing the valve check I noticed that the 'I' in the HI in the plug window didnt match exactly in the ticks with the dots on the cams at 9 oclock and 3 oclock where they should be, before I took it apart. If I put the dots at 9 and 3, then the ' I ' would be about 1/4 inch off or on the left side of the plug window. Is this normal or something that could cause a problem?

When I put it back together, same issue. If i moved the gear one more link, it would be way off, so it went back together like i found it.

Is this a sign that the timing chain stretched? Also, the shims that were in there were stock shims i think, so I dont think it's ever been apart.

(I bought the bike 3 months ago and has been running great until this)

  • Sj1

Posted February 19, 2012 - 10:13 AM


I was able to pull it before the wife got ready to leave...

Here's the plug, crappy pic i know, but it's dry black around the edges with a clean electrode.

I also tried to blow air in with my compressor, but i need a longer tube to get a better seal.

Posted Image

  • MANIAC998

Posted February 19, 2012 - 12:31 PM


That looks clean. Clean enough to not cause the issue anyhow. Hmmmmm...........anyone else? Maniac

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  • johndeerekid

Posted February 19, 2012 - 10:34 PM


ive had that happen to me. i found that the spring at the bottom of the decomp lever at the motor had spun around and wasn't doing its job, i just repositioned it back to where it was supposed to be and it fixed it. also i recommend taking your carb off and going jet by jet, and hole by hole blowing them out with a compressor, because its always a good idea to clean them because even the tiniest spec of dirt can have a huge effect with carbs. they're very sensitive. -Wes

  • Sj1

Posted February 20, 2012 - 10:32 AM


Thanks Wes, That solved the decomp issue, now that works right.

A note to anyone who reads this in the future..the little hook on the spring goes on the bottom and the straight end of the spring gets caught on the engine.


So, I bought a compression check gauge just to put my curiosity to rest, but I have no idea how to get a good reading.

Does anyone know the procedure? Decomp lever, then kick, or push it with it in gear, decomp lever, drop the clutch and hope you get it to turn over?

With the decomp lever then kick method, the highest i saw was 90psi, but i dont think this is the right way to do it.

  • Sj1

Posted February 20, 2012 - 01:31 PM


So I took it apart again today to re-shim the middle intake that was still at .10. It's now at .15, so all valve clearances are within spec at the higher end of the tollerances.

It started right up after a bit of a struggle with the decomp lever again (yes the spring is in place still). It seems to gain compression again before I'm done with my kick and stops abruptly.

Now that I have different shims in there do I need to adjust the decomp cable?

My start routine:
  • Pull decomp lever
  • kick 1/4 way
  • release decomp lever
  • kick hard and fast for a full cycle
  • it starts.
Instead here is what happens
  • Pull decomp lever
  • kick 1/4 way
  • attempt to kick it through
  • stops half way and becomes rock hard.
  • pull decomp lever again, kick flows through to bottom.
I didnt take it out for a test ride yet due to this starting issue.

Here's how the cams are matched up with TDC.

Posted Image

Posted Image

  • MANIAC998

Posted February 20, 2012 - 04:04 PM


Cam timing looks good. As for my starting routine when kick starting, I push down on the kickstart lever until you feel resistance, THEN pull the decomp lever in and push down on the kickstart so that it moves about an inch. Then let out the decomp lever, and return the kickstart to the full upright position, remove hand from twist grip, and give the bike a solid kick all the way thru it's travel.

You can do all of this with your foot on the kickstart lever, I just used the term "push" so as to emphasize the fact that your not trying to kick it until you've got the kickstart lever fully upright after using the decomp. to get it past TDC.

This sounds waaaaayyyyyyy more complex than it is. Within a couple of kicks, it becomes second nature. Hope this helps. Maniac

  • Sj1

Posted February 21, 2012 - 05:08 PM


I gave up...its at the shop. :bonk:

  • Sj1

Posted March 01, 2012 - 09:17 PM


Got it back from the shop the other day...I had them double check my work on the valve clearances, said everything was all good there. So, at least I know how to do that in the future. They said there was likely no damage/association with the initial oil change mistake.

So that left the carb as a suspect. They also said the gas tank breather valve was plugged which could restrict fuel flow, but that was most likely not the main issue regarding stalling on decel.

When they went through the carb, they actually found bits of rubber in there from the fuel line degrading. The previous owner used some black rubber hose from autozone or something. They cleaned everything up and put in a bigger pilot jet. The thing runs like a BEAST now. Fires on the first kick, has a little more grumble to the idle and pulls hard down low. Feels noticably quicker, more responsive and pulls the front wheel up way sooner than it used to and more importantly, doesnt die or stall out.

I also, had new fork seals put in while they had it. Should be good to go for a while now. Couldnt be happier! Glad it wasnt something more serious.

btw...The Pit Enterprises in Phoenix did the work if anyone local is looking for a descent shop.

Edited by Sj1, March 01, 2012 - 10:07 PM.


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