The rotax engine maintenance manual tells you how to set up the exhaust valve with the engine on the bench. I would be very interested in opinions on several matters:
1) What effect does winding in the adjustment actually have on track. Some say you have to wind it 10 clicks to notice a difference, others say changes can only alter the timing of opening the valve by a maximum of 500 revs. What do experienced racers feel about this?
2) When fitting a new bellows, what length do you set the blade at, and if you set it shorter or longer is there a benefit? Two major (renowned) engine sealers in UK give me different advice.
3) Is there a trend to use the exhaust valve like a carburettor and move it between engines as one would do with a favourite carburettor?
4). Is it of any importance to remove the internal spring when the engine is stored (ie between race weekends) to "rest" the bellows"?
5) Anyone got any favourite tricks to share - I am on another continent!

I usually test it on track making fairly large adjustments of about 10 clicks and narrowing it in from there. Takes about 4 laps or so to get it about right.


What advice did they give? :O I probably haven't paid enough attention to the length. It does seem that there should be one ideal length outside of which you are losing performance somewhere - it won't be flush in the "open" position if it isn't set right.


I start looking for another exhaust valve when one is giving me trouble.


Interesting... doesn't sound like a completely pointless exercise to me. Maybe extend the bellows lifespan.


Always keep it clean to ensure consistency. [/quote]

1). Testing will reveal this answer but ours always stays the same, 10-11 clicks from full in.
2). I do not believe the "blade length" is critical. The valve is either open or closed, nothing in between for all practical purposes. The open position is controlled by the body of the blade hitting the o-ring which is then pressed against the RAVE body. Thus the opening position cannot be controlled by the length. Similarly, the closed position is controlled by the body of the blade hitting the machined surface of the cylinder. What is important is that the bellows has enough travel to comprehend this overall movement and that the length doesn't change during the session (use Loctite).
3). I have a spare for immediate replacement so that I don't have to rebuild the RAVE in the short period between sessions. But nothing "special".
4). We always remove the red adjuster at the end of the day because we have experienced the bellows taking a "set" after leaving the spring in place for several weeks. Probably doesn't hurt, but since bellows are expensive, why take the risk?
5). I will send a PM with "secrets"

ohh 1st post already with secrets? damn, may you shoot a PM toward me too..


hehe i tho that was funny