Decomp. lever mishaps



18 replies to this topic
  • yamie_rider

Posted January 28, 2002 - 02:01 PM

#1

Has anyone wrecked there 250f of 426 by accidently pushing the decomp. lever . I have crashed on mine many times and the engine is still fine.

  • YZ400Court

Posted January 28, 2002 - 02:05 PM

#2

The shop that does my motor work grinds down the actuating pin in the engine. Where it comes in contact with the valve cap, they grind it down so it just barely opens the valve. The thought was if the lever gets hit, this would stop major damage.

  • yamie_rider

Posted January 28, 2002 - 02:17 PM

#3

I am thinking of cutting half my lever off.

  • Hick

Posted January 28, 2002 - 03:50 PM

#4

Originally posted by yamie_rider:
I am thinking of cutting half my lever off.


Why?

  • yamie_rider

Posted January 28, 2002 - 04:07 PM

#5

So its theres less chance of it getting it gettin pushed in a crash, just an idea. I saw a tm 400 on the weekend and its decomp. lever was half the length of the yz.

  • bbeakley

Posted January 28, 2002 - 04:38 PM

#6

I don't know if there is enough lever throw, but the new CR450F has a sweet set up with an integrated clutch/decomp lever. There is very little chance of actuating the Honda decomp lever in a crash. I don't know a price yet, but I keep checking partsfish.com to try and find out what it'll run.

  • Hick

Posted January 28, 2002 - 04:43 PM

#7

I still don't get it. Why are you worried about the lever getting engaged when you drop the bike?

Well, it will kill the motor, but by this time I'm assuming the bike is upside down, or was briefly, in which case it is likely going to die before you can pick it (and yourself) back up anyway.

If you are thinking the valves will hit the piston, if this was possible it would happen when you kick the bike over with the lever engaged.

Go ahead and try it. Get up to about 40 or so in 5th and pull in the lever. It helps nicely with engine breaking but will not harm the engine.

There is also not much chance of bump starting a WR/YZF without the decomp lever, which I find myself doing all the time. So far I'm on my second YZF, probably have about 250+ combined hours and have never had a valve bump into a piston and I’ve always used the decomp for bump starting, at all engine speeds.

This may not be true for every bike, but pulling the decomp with the motor running is harmless on a WR/YZF.

Hope this is helpful/informative.

  • freestyle111

Posted January 28, 2002 - 08:45 PM

#8

i use my decompression lever to kill my bike all the time.as a matter a fact my kill switch was broke for 2 months so decompresson lever was my main sorce for killing engine.i also use decompression to help bump

  • Hokie

Posted January 29, 2002 - 06:11 AM

#9

Originally posted by bbeakley:
I don't know if there is enough lever throw, but the new CR450F has a sweet set up with an integrated clutch/decomp lever. There is very little chance of actuating the Honda decomp lever in a crash. I don't know a price yet, but I keep checking partsfish.com to try and find out what it'll run.


You can get one works connection, also.
Kinda pricey but I never broke the decomp lever
after getting the integrated lever/perch.

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  • DirtJunkiexxx

Posted January 29, 2002 - 09:10 AM

#10

listen to Hick he's got some Mad Knowledge! :)

  • yzf_virgin

Posted January 29, 2002 - 10:56 PM

#11

How do you use the decomp to bump start?

  • Hayseed

Posted January 29, 2002 - 12:58 PM

#12

Originally posted by yzf virgin:
How do you use the decomp to bump start?


How do you bump start without it?

Under most conditions trying to use a WR/YZF’s momentum to spin the motor via the tire, chain and transmission (bump starting) only results in the rear wheel locking up.

This happens when the engine reaches TDC (top dead center) on the compression stroke.

So there ya are, cookin’ along, and you brake stall it. DRAT!! But you still have some momentum so you quickly dump the clutch. But the high compression of the YZF foils this meager attempt at a restart and the rear tire locks up!!

What to do?

You must use the compression release lever to get the motor beyond TDC, much like you need to when kick starting it. Just pull and quickly release the lever and the motor will spin past TDC and two revolutions later will return there with enough momentum to fire.

Soon you will be instinctively reaching for the comp. release lever when you stall it, you need not even bother with the clutch if you can feather the compression release quickly enough.

Hope this helps.

  • CAL

Posted January 29, 2002 - 03:13 PM

#13

Originally posted by bbeakley:
I don't know if there is enough lever throw, but the new CR450F has a sweet set up with an integrated clutch/decomp lever. There is very little chance of actuating the Honda decomp lever in a crash. I don't know a price yet, but I keep checking partsfish.com to try and find out what it'll run.


I thought the CRF's had automatic decompression? And the lever on the perch was a remote hot start?

  • bbeakley

Posted January 29, 2002 - 05:25 PM

#14

Ah, my red bike ignorance shines through. I saw the little lever, assumed it was a decomp lever (even though I know they have auto decomp, some bike have both). That's a cool hot start if that's what it is. Thanks for the info.

  • Looped_Out

Posted January 29, 2002 - 07:09 PM

#15

I thought the CRF's had automatic decompression? And the lever on the perch was a remote hot start?

Does the hot start lever on the CRF use a cable? If so, can that set up be used for the comp relese on the YZF?

  • Looped_Out

Posted January 29, 2002 - 07:12 PM

#16

Sorry, I didn't do the quote right, but you get the idea, right?

  • krazyq

Posted January 30, 2002 - 04:48 AM

#17

Did someone ask why ;and said they use the comp. lever to shut off thier bike?
This lever dumps the exhaust valve in. Thus releasing the compression(easy kick) .Doing this in a fall or to shut down the bike is NOT GOOD.You could dump the valve into the piston causing unthinkable dammage.
To avoid this I used the cable screw and set it all the way in giving me about 1 inch of play.This when fully engaged lowers the valve much less now the valve dosent go in as deep thus avoiding the problem to some degree.

  • Hayseed

Posted January 30, 2002 - 11:51 AM

#18

Originally posted by krazyq:
Doing this in a fall or to shut down the bike is NOT GOOD.You could dump the valve into the piston causing unthinkable dammage.


Actually, the valve stays in the head and will not fall into the cylinder or otherwise contact the piston.

I don’t know where this notion comes from. If it was gonna hit the piston it would do so when you kick it over with the release pulled, which I’m fairly certain everybody has done at least once.

Thank you.

  • herbski

Posted February 01, 2002 - 10:44 PM

#19

I have kicked my 01 over w the decomp pulled to clean it out after a crash and had it start.


Herbski





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