killing the bike

any harm, in killing my yamaha wr400f -98 with the compression release lever??

my kill switch doesn't work, so this is the only way I could stop the engine...

I would use the hot start or choke. Better yet fix the kill switch


Tough question. I will bump start mine using the CL to help it turn over the first time. I have accidentally hit it while running. It probably gets hit during some falls. After rearranging my levers, each time I turned the bars to the right, it would die and it took a couple of days to figure it out. So it probably won't hurt to use it. But it sounds bad.

People have two issues with using the CL except when dead, burned valve faces and seats and valves dinged by the piston if down when the piston comes up. I think I can vouch for the piston hitting them because the time I grabbed it while riding, I heard what sounded like a knitting machine. It could have been the CL actuator but I believe it was the piston. Unlike a mistimed cam which will break valves, the valve isn't held down firmly so the piston can push it back up but it can't be good for it.


I will be disagreed with but: VERY BAD IDEA

That jackhammer sensation you feel when you do that IS the piston hitting the valve. Never a good thing in any engine, anytime.

I guess that is another good thing about having a B.D. Dual Sport kit: 2 kill switches. :)

put the bike in gear and let the clutch out slowly...this will also stall out/kill the bike!

Originally posted by Chaindrive:

That jackhammer sensation you feel when you do that IS the piston hitting the valve.

I believe it's the valve hitting the compression relief shaft as the valve opens and comes back down on the shaft rather than the valve seating.

I frequently just dump the clutch with the brakes on to stall it. Mine starts just fine in gear (with the clutch in) most of the time anyway.

[ April 13, 2002: Message edited by: John H ]

fix the kill switch!!its only 2 wires.


Just fix the kill switch!!

Like freestyle says its only two wires.

I can post photos of where they connect to if it helps you. Just buy a new switch and wire it in.

The later Euro spec bikes have a combined light switch and kill switch, is yours the same? Even if it is you could buy an aftermarket kill switch and wire it to the black & white wire under the tank. If it is a two wire kill switch wire the second wire to the black wire next to it - or any earth wire or earth point.

The photos would help, so I'd appreciate if you could post them. I got the light switch/blinker/horn/kill switch combination... only the light switch works at this time.

From the manual "CAUTION never use the decompression lever after the engine is started. the engine may be damaged"

You might as well tear it down now. This will give you the excuse to install that 13-1 piston you always wanted.

If you have ever done your own valve adjustments on you bike you would find that the compression release tab sits on the upper edge of the tappet, when you pull the compression lever it pushes on the tappet so slightly you can barely notice it. I have been using the compression lever for different purpose's (Bump Starting/releasing engine braking for three years) I do regular valve adjustments, and like many others have had NO PROBLEMS....I was told from the start from professional Yamaha mechanics (Factory/Local) that the damage to the bike because of the Compression lever utilization while running was a myth from the begining.

Bonzai :)

Well, after thinking about it I am not sure for these two reasons:

1 -- If you are clearing the cylinder, you are holding the comp. release while kicking through multiple full strokes. This does not seem to be a problem.

2-- I have had my motor lock up and bend the exhaust valve due to not having enough slack in the comp. release cable.

I personally would not take the chance, its too expensive and too much time if a failure occurs.

Fixing the kill switch is a much better idea.

How do I add an attachment??

I have a word document showing the wiring and a bit of explanitory text, but cant figure out how to do it.

I guess I need somewhere to host the file so I use the URL? I dont have a website of my own.

Laba - Send me a PM with your email address on it and I will email it.



I change my vote. I said I could vouch for the valve tapping the cylinder because I could hear it, it sounds like a knitting machine.

John H, Yamakaze, and others were right, I was wrong. I just happened to be putting the head back on tonight and checked it. After putting the cams on, I pulled the decomp lever, rolled it through a few times and (1) the valve does not hit the piston (longshot, if hot and high RPM, naahh, it just doesn't) and (2) when the exhaust cam passes and the bucket comes back up, it clicks, creating the knitting machine sound I heard. Next time, ignore my posts and read John H's instead.


p.s., I am proud to say I used the scientific method. Hypothesis: if the piston hits the valve when the decomp depresses it, I will hear it. Test: pull decomp while running. Result: heard clicking. Conclusion: piston hits valve. This must be the scientific method that predicts global warming or requires protected thousands of square miles of desert for a tortoise so depopulated it may become extinct. If so few of them, why do they need so much land?

Use the compression lever for what it's for and thats it!! Fix the kill switch or just dump the clutch. Don't be a fool and put any unwanted strain on the motor. Two wires is all it takes to fix the switch. You can connect them any way you want becauce the switch is just a normally open curciut. I've already reconnected mine and placed it in a different location on the bars after it was pulled off by a tie down.

Steve, I agree, the priority should be to fix the Kill switch....But...The purpose of this forum is to provide assistance and some training to those who need it and want it. It is also to dispell untrue rumors such as this one...

Like my hero Joe Friday always said: JUST THE FACTS MAAM :D

Bonzai :)

It's still a bad idea, over time it can deform the bucket and cause it to stick. In turn, causing engine damage.

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