push start



12 replies to this topic
  • az426

Posted July 12, 2001 - 12:58 AM

#1

hey there found a easy way to bump start the
bike.go thru the tdc/decompression/hot start routine then push or bump(downhill) starts way easier especially for us vertically challenged folk.nothing revolutionary just thought i'd add for the newcomers.

  • WR_Jason

Posted July 12, 2001 - 04:44 AM

#2

I once tried to bump it sliding down a loose gravel hill and it would not go. Thats the only time I tried it. I herd a few guys shredded their clutch baskets bumping it, so I may try it once or twice to make sure I can do it, but Im not going to make a habit of it since I am not verticly challenged and have lots of leg to spare :)

[This message has been edited by WR_Jason (edited 07-12-2001).]

  • sirhk

Posted July 12, 2001 - 07:35 AM

#3

I don't know if it's bad or not but I wait till I have quite a bit of speed built up and then let out the clutch keeping one finger on the Decomp. lever. If it starts to skid I just quikly pull in the D. Lever all most like a tap not even pulling it all the way and it lights right up everytime. It's basicaly just enough to get it over TDC

------------------
Khris
"What's that?"
"It's a Yellow 99' YZ400!!"

  • nozzlejockey

Posted July 12, 2001 - 06:07 PM

#4

DONT! According to my dealer you can bend your valves due to the placement of the valves and piston while it's running. Sorry for being so infatic, but I am currently on an engine rebuild right now and am paranoid about doing anything against the manual. 2001 426 six months old :)

  • Hick

Posted July 12, 2001 - 06:20 PM

#5

Originally posted by nozzlejockey:
DONT! According to my dealer you can bend your valves due to the placement of the valves and piston while it's running.



If you could bend them bump starting it, then you would have already bent them kick starting it.

My dealer is a complete f***in idiot too.

  • WR_Jason

Posted July 13, 2001 - 05:27 AM

#6

Thats true, you use the decomp lever to get the pistion over Top Dead Center, thats the closest the piston comes to the valves. I dont think there is a risk of valve damage, I just herd a guy say he dropped his clutch basket doing it. I think it was on a 98 though, they had some basket trouble. I wont hesitate to bump her on a down hill if she stalls, I just have to practice. I am going to try moving the decomp lever to the right side, shold make for easier starting while in gear and shold make bumping her easier too. I upped my idel to avoid stalling at all cost, I did have to put some water in it though last weekend when she pushed about one quart of antifreeze out on a slow trail ride.

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  • Shawbridge Husky

Posted July 13, 2001 - 06:49 AM

#7

Why risk expensive damage? I can probably kick start faster than trying to figure out how to bump start it. I read here about feeling the valve being pushed closed through the decomp lever. True or false, my life is complicated enough to keep away from it!

  • Hick

Posted July 13, 2001 - 01:19 PM

#8

Originally posted by Hugh LePage:
Why risk expensive damage? I can probably kick start faster than trying to figure out how to bump start it.


That makes sense, but there is no risk of damage. Zero, zilch, nada.

Plus I’m sure that anybody can bump it much quicker than stopping, finding TDC, and kicking. When I stall it I instinctively try to bump it, even if I’m barely rolling. I have successfully restarted in a sand wash, in deep braking bumps, in a corner, in first gear, during a race. I’m sure this saved me at least 30 seconds, and there was a guy who finished about 40 behind me...

If you run the motor with the decomp rod riding or pressing on the shim bucket (but not enough to open the valve) the bucket and possibly cam and head can wear improperly or become damaged because the decomp rod will prevent the bucket from rotating, which it does by design to promote even wear. So make sure you have some free play in your decomp lever.

Of course if the decomp is engaged all the way the motor will die.

In short, it is possible for the decompression system to cause engine damage, but not while you are trying to start it. And I don’t care if anybody’s dealer, mechanic, salesman or girlfriend told them differently, they are wrong.

:)

  • motoman393

Posted July 13, 2001 - 06:23 PM

#9

Bump starting works great! One time I was clearing a 110ft tabletop and while in the air I hit the rear brake w/o using the clutch (and of course my bike died in mid air)! So reacting really quickly I pulled the clutch in (while still in the air) and when I landed I let it out and I started and I kept going! But boy did that scare the crap out of me! LOL

Garrett

------------------
I get my kicks on a 426!
Motoman393's MX Site

  • ricky1

Posted July 14, 2001 - 05:37 AM

#10

Hick

Thanks for the post. I bump start mine whenever possible. I almost never use the decompressor. I always shift to 5th, bump it, as soon as it turns over start downshifting fast. Don't give it any gas until you hit the proper gear.

------------------
Rick Fuller
'01 yz426
'00 yz426 destroyed by fire in desert race 4/22/01
'81 490 Maico

  • sirthumpalot

Posted July 14, 2001 - 09:27 PM

#11

Just to add food for thought, in my 01' manual on page 1-14 it says:

---
"Never use the decompression lever after the engine is started. The engine may be damaged if you use the decompression lever while it is running."
---

I won't speculate as to the type of damage they are referring to, but I wonder if it is possible to get the valve to hit the piston if you pull the lever all the way back to the handle bar?

  • Hick

Posted July 14, 2001 - 11:43 AM

#12

Originally posted by sirthumpalot:
I won't speculate as to the type of damage they are referring to, but I wonder if it is possible to get the valve to hit the piston if you pull the lever all the way back to the handle bar?


No.

  • rob1980

Posted July 14, 2001 - 04:21 PM

#13

I agree, it won't cause any damage at low engine speeds, the engine is designed so that it will clear the piston when the lever is pulled in. That said, I wouldn't be pulling it in at 11,000rpm to test the theory.
Also, I thought the idea of a manual decompressor was to 1. Aid finding TDC and 2. Aid in roll starting a stalled engine.
I have always used them for roll starts on all the bikes I have had, and have had zero problems.





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