Maintenance & Technical > KX500 Original

Exhaust valve timing..?

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John:
Has anyone investigated (verified) the opening times for the exhaust valve in relation to engine RPM?s?

If you are familiar with the principle of how the exhaust valves operate, you know that the opening times are controlled by a spring loaded mechanism.

It would be possible to change the opening times by fiddling with the spring pre-load and the K value of the spring itself.

I am not saying that this is something I particularly want to do, I was just wondering if someone has done anything in this area and would like to share their findings.

I think it would be possible to set up the whole axle with the balls and spring in a lathe and crank up the rews until it opens. I guess there are lot?s of opportunities for false reading given that the axle is not in its native environment - lack of friction and resistance and all.

Just wondering?


On the same subject;

Would there be any benefits in changing the exhaust valve timings? Maybe this could be a cheap (and easy) tuning tip?

//John

YUNGGUNNAZ:
john,good question to explore.my opinion is there should be some gains in changing the exhaust timings if other factors such as transfer hgts.,exhaust widths,intake openings etc.as well as pipe and intended use of bike. did not have time this year to experiment with governor spring or ramps to see what i could come up with.sure there are gains here.did tinker with rm250  spring and tension on return spring and it picked up revs quicker.i'm pondering blocking off the exhaust port drumm openings and center valve in order to control timing more for my use,which is drag race.this thread should be interesting.

IridiumRed:
This would be an interesting test to do - running the gov in a lathe and watching the behavior at various rpm

I wonder how much the governor behavior (such as the RPMs when it begins to open, fully opens, etc)

I know the powervalve makes a HUGE difference in the way my bike runs.  I should know, I had problems with mine for a while (dirty powervalve system, overclosing valves, etc), so I played around with it, disengaging it completely (leaving it closed), leaving it wide open, etc

This might be a fairly substantial reason why one KX500 runs differently from another

John:
Just writing something to keep the topic going. I can't be bothered to do anything myself .  :oops:

//John

YUNGGUNNAZ:
john,i don't have a lathe here to turn it that fast.but i did take a look again at the rams and balls and decided to modify ramps some to see how it actually makes the bike react.i assume it will allow the balls to climb ramps faster and open valve sooner maybe getting motor on the pipe a little quicker.still plan to spinn it to visualize effect.

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