Pulling Decompression Lever while engine running

10 replies to this topic
  • Sigtober

Posted February 27, 2006 - 05:40 PM


The other day I had my bike running and wanted to see what would happen if I pulled the Decompression Lever. The engine shut off. Is this bad for the bike? :thumbsup:

  • jbrooks26

Posted February 27, 2006 - 05:53 PM


I wouldn't recomend using the decomp lever as a kill switch, but you should be ok. There is a chance that if your piston to valve clearance is not right you could contact the piston with the valve doing this. In other words, don't get in the habbit of doing that. Accidentally now and then is not something to loose sleep over. Hope this helps.


  • grayracer513

Posted February 27, 2006 - 07:36 PM


At any speed much over an idle there is a risk of breaking the exhaust valve lifter as a result of the rocking load applied to it by stopping against the decomp shaft. It's OK to use it for bump starting, but at higher speeds, including idling, it gets risky, and should not be done.

  • idiot_on_426

Posted February 28, 2006 - 10:21 AM


hey, i noticed that you have a nice modification set up for your carb. i have a 01 yz426 and was wondering if you know if i did the exact same mods that i would do the same amount of turn on the fuel screw as you did, since yours is a wr and mine is a yz, is it the same? thanks

  • jbrooks26

Posted February 28, 2006 - 11:27 AM


They will be similar most likely, but the fuel screw setting is a never ending adjustment. Think of it as a fine tuning, you adjust it almost every ride for optimum throttle response. It also provides a guideline for the pilot jet. Less than 1 turn out and you need a smaller pilot, more than 2.5 turns out and it is time for a larger pilot. I do recommend the JD kit, it gives you much more range of adjustment and also improves performance. Hope this helps.


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  • idiot_on_426

Posted February 28, 2006 - 05:27 PM


thanks, how much did u pay for your jd jet kit, do you know how to get it cheap, im kinda short on 70 dollars

  • jbrooks26

Posted February 28, 2006 - 07:07 PM


Bought mine on from the TT store. I suppose you could watch E-Bay, but I would just wait until you have the money and get it from TT. They have a low price guarantee, and the customer service is great.


  • villiage_idiot

Posted February 28, 2006 - 07:56 PM


I had a branch grab my de-comp lever and kill it. I was terrified that a valve and piston had collided. They didn't, fired right back up and I was on my way. Few hundered feet down the same trail a branch snagged my front brake lever and I ate it pretty bad...lol.

  • TimFurryBalls

Posted February 28, 2006 - 08:21 PM


One word: Bark Busters. Oops. That was two. :thumbsup:

  • villiage_idiot

Posted February 28, 2006 - 08:26 PM


One word: Bark Busters. Oops. That was two. :thumbsup:

They are on "the list". :thumbsup:

I run shorty bars already, great for tight work but man-o-man do they ever work on the shoulders. I rode a friends KTM with pro-tapers and it was like a Cadillac in comparison, but I utilize the shorter bar length alot and can't decide if I wanna go full length.

  • grayracer513

Posted February 28, 2006 - 08:42 PM


The exhaust valves will not hit the piston as a result of pulling the compression release at any speed unless the lifter becomes damaged. It doesn't hit when you crank it, does it?

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