Running engine on the stand...

[Cement Legs]

Bottom line, is it a nono to run the engine through its gears with no load on the drive sprocket? ie no chain.

[Cement Legs]

Bottom line, is it a nono to run the engine through its gears with no load on the drive sprocket? ie no chain.

[VFR750R]

Perfectly fine to do, although I have to ask... why this is important for you to do?

[EgyptianMagician]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by VFR750R:
Perfectly fine to do, although I have to ask... why this is important for you to do? <HR></BLOCKQUOTE>

We were hoping to be able to test the pneumatic shift system, and to ensure that all our gears are working fine.

We successfuly started the engine a few weeks back, but kept it in neutral. Someone had mentioned that it might be a bad idea to run the engine through gears at high RPMs if there was no load ...

thanks man !

[GTmule]

I'd be alot more concerned about the engine at high rpm, and no load.

[Agent4573]

I would think you'de see the same problems running gears through high speed testing with not load as you would with running an engine through high RPM testing with no load. It might not break, but its probably not good for it. I believe we do run our engine up to speed on the dyno stand stand though before applying any actual loading to it, and the engine has lastest a very long time, but its also outlasted everyone's expectations.

[rjwoods77]

The only thing you have to worry about is not letting off the throttle quickly. In close tolerance interference engines, if you dont have the engine under load, you run the risk of valve collisions at high rpms with sudden reduction in throttle angle. Each engine is different.

[Frank]

bottom line = no problems

[VFR750R]

Rob, I'm interested in what engines throttle postion has an effect on valve to piston clearance. I guess the engine would have to have lot of cam timing slop where under fast deceleration the cam shaft will take up the slack in the opposition direction it normally does, am I thinking right??

I can't imagine a problem, I know some people are under the illusion that without load the rod will stretch more allowing piston to head contact in engines running tight deck clearances but what about the other cycle, there is nothing to keep the piston from hitting during overlap during any load condition.

[rjwoods77]

If the seat pressure isnt high enough to keep the valves from floating because under no load the cylinder pressures arent helping push the valves against the seat. I have heard of this from around the way with engines that are designed to have just enough seat pressure to make the valves operate under normal conditions well. More seat pressure equals for losses beyond "what you need". I was just mentioning it as a possibility. But just like everything, what I heard could be wrong.

Sudden reduction in throttle was meant to mean spiking the pedal and letting off. You would have to have some real close tolerances for this to happen if it is true.