decompression lever?


17 replies to this topic
  • Jo77

Posted August 19, 2007 - 01:53 PM

#1

i was watching my bike today and i think its better to change the point of my decompression lever upside down to protect it from get broken if i have a fall.(yz426f).your opinion?

  • 642MX

Posted August 19, 2007 - 03:33 PM

#2

I didn't like my decompression lever either. So I took it off and put an auto decompression cam in. Its the best $100 you can spend.

  • nolzey

Posted August 19, 2007 - 07:44 PM

#3

i have put mine under the cluch lever, protects the motor from blowing up if you flip your bike and the decomp lever gets pressed at a high rev. its still easy to use aswell.

  • Jo77

Posted August 20, 2007 - 06:35 AM

#4

yes i think its better to move my decomp lever to a safe place!if i touch it by a mistake while rynning motor or get pressed in a fall while the bike is still rynning will damaged my motor or nothing its going to happend?

  • Thomas6x

Posted August 20, 2007 - 12:10 PM

#5

I raced an 99 400f for a few years and crashed a lot.Never had a problem with the lever being turned up.No you will not hurt the motor if pulled while running.Once in an AX race I staled in the whoopes at the end of them, I managed to hit the lever and it bump started back up and shot out of them. Never lost my place.Just my 2 cents worth.:applause:

  • USED YZ426F

Posted August 20, 2007 - 01:33 PM

#6

yes i think its better to move my decomp lever to a safe place!if i touch it by a mistake while rynning motor or get pressed in a fall while the bike is still rynning will damaged my motor or nothing its going to happend?


If you pull it in and hold it long enough your engine will die. No permanent damage will be done, you will just have to restart it.

  • King_Air

Posted August 20, 2007 - 02:20 PM

#7

I put mine in a very safe place. The garage shelf and installed the decomp cam. Best mod for this bike. Just do it!

  • Jo77

Posted August 20, 2007 - 10:48 PM

#8

my bike starts easy now by the 3rd kick when its cold so i dont want to for now at least to do the 450 cam mod.maybe later.what i was worried about its if the motor get any damage when the decomp lever get pressed by a fall or by mistake while running.from what i ve read of you i m calm now a bit that nothing happens.

  • nolzey

Posted August 20, 2007 - 11:10 PM

#9

in was told at full noise it can do damage, from my local dealer (parts). i have hit mine while running and did no damage but i was not in high rpm.

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  • Jo77

Posted August 20, 2007 - 11:18 PM

#10

in was told at full noise it can do damage, from my local dealer (parts). i have hit mine while running and did no damage but i was not in high rpm.


THANKS MAN!i m going to keep an eye on my lever while running!i get used to it anyway!

  • Jo77

Posted August 20, 2007 - 11:20 PM

#11

grayracer513?what do you think?reading a lot of your posts here and i respect you a lot for your help to yamaha riders!:applause:

  • grayracer513

Posted August 21, 2007 - 05:59 AM

#12

in was told at full noise it can do damage, from my local dealer (parts). i have hit mine while running and did no damage but i was not in high rpm.

It does have the potential for it. For one thing, the compression release increases the valve clearance on that exhaust valve to about a full millimeter, which simply isn't good for anything involved at higher engine speeds. For another, the valve is stopped as it closes, not by seating gracefully against the concentric valve seat, but by being stopped abruptly against a hard stop at the edge of the lifter. It is designed with all this in mind, of course, but the CR lever does impart a rocking force to the valve lifter, which could conceivably break it under the wrong circumstances.

This is not to say that you should be afraid of it, just try not to let it engage while the engine is above, say, 4000 RPM, or so. Using it to bump start, etc., is harmless.

  • Jo77

Posted August 21, 2007 - 12:25 PM

#13

thanks a lot!i keep that in mind!:applause:

  • 00YZ426FMRCD

Posted August 21, 2007 - 01:59 PM

#14

I put mine in a very safe place. The garage shelf and installed the decomp cam. Best mod for this bike. Just do it!


DITTO!

  • cowboyona426

Posted August 21, 2007 - 08:11 PM

#15

Just get the 03 cam and lose the lever, I guarantee you won't be disappointed.

  • shrekka

Posted August 22, 2007 - 01:16 AM

#16

couldnt agree with you more about changing to the 03 cam.
i have a 2002 YZ426 which l use in the bush, and getting rid of the decmp and changing the cam was the best $$ lve spent on the bike. the power difference is great too


Shrekka

  • micah600

Posted August 22, 2007 - 10:25 AM

#17

Greyracer- You'd better check your decomp adjustment- If you've got .040 valve lash and your lifter hits the decomp arm when running, you've got some serious issues. Or at least you will.

  • grayracer513

Posted August 22, 2007 - 11:02 AM

#18

That isn't what I said.

In an otherwise correctly set up engine, using the compression release will lift the left exhaust valve off its seat about 1 mm. Since the cam does not move, that valve effectively has 1 mm of valve clearance (+ what it had to start with) for as long as it is "running" with the CR pulled.





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