Rotax power valve spring

Sam Cooper · Posted: Mon Aug 12, 2002 9:14 pm Post subject: Rotax power valve spring

I have been told that the spring located inside the power valve cover has no purpose, and makes no difference if it is in there or removed...

I have even been told most new motors don't even come with them.. is this true?

Sam Cooper

Mikko Nassi · Posted: Tue Aug 13, 2002 1:44 am Post subject: Rotax power valve spring

If you're racing against me, and you're fast...then yeah you're right, the spring is useless, take it out.

But since you aren't.....the spring has a reason in being there, leave it in.

Marshall Mauney · Posted: Tue Aug 13, 2002 5:06 am Post subject: Rotax power valve spring

If you look at the design closely, you'll see that the spring is what holds the valve in the exhaust stream under low RPMs. When the RPMs increase and put enough pressure on the valve to compress the spring, the valve pushes out of the exhause stream, opening the pipe up for more flow and less backpressure. The red adjustment screw varies the length of the spring in the closed position, thereby changing the force required to compress the spring and open the valve. This is what changes the RPM value that causes the valve to open.

It follows that if you change the spring, you'll have to re-set your powervalve. This is also why otherwise 'equal' motors require different powervalve settings to operate the same; not all springs are created equal....

Marshall Mauney

[ August 13, 2002: Message edited by: Marshall Mauney ]

Nick Weil · Posted: Tue Aug 13, 2002 5:32 am Post subject: Rotax power valve spring

Sam,

I agree with Mikko. Bombardier is not in the business of sending out a part that may or may not come with the motor, that you may or may not need.

But now that you mention it...

every 1000th motor that Rotax ships comes with a small wiring harness attached to the existing wiring harness. This 'extra' harness is for wiring a boost system which Rotax only sells to those who can provide the serial # from the back of the boost button. I was glad when I got lucky enough to receive the 1000th motor in our recent shipment. I would be willing to sell it to you though because you seem like a pretty trusting guy...

Nick Weil