Rotary valve degree

[jwick86]

I have been looking around at changing out the rotary valve on my 97 GTX as from what I'm reading its a simple and quick upgrade. I know the stock one is 159*, and from what I'm reading people are lowering the duration. Just curious what lowering does and what raising the duration will do on these motors? Also when reinstalling the valve do I set it to the factory specs?

 

[timmyboy76]

whats the motive...

think, if you start tweek'n w/it, but your ski is stock, than i'm sure you'll runinto probs. Ski calls out with, 159*RV, with 147*opening, 65*degree closing. So, with "mag" piston,TDC, you can then remove the rv if need be, and you'll have the mark'n for realignment, if off, flip plate around

 

[jwick86]

I understand how to put the RV back in, I have the Seadoo manual for most models from 96 to 05 I believe. I was just wondering if changing the duration would gain me anything in performance. Not necessarly looking for HP but even throttle response. Does anyone know what will happen by giving it more duration or less duration? This is my big question as I am curious to learn this.

 

[seadoosnipe]

Modding?....

Because I'm not heavy into modding these things (yet), I don't know an exact answer to this question, but a theory.

If you change the degree of the wheel, then your only changing the amount of fuel the combustion chamber gets by the amount of vacuum you create when the cylinder is in intake stroke.

The degree wheel is set with the mag piston at TDC. If you want to create more power, changing the timing in 4 stroke applications, you advance or retard the timing. I don't think this would work in the rotary valve's timing, since this is just a way to create the proper amount of vacuum to draw in the correct amount of fuel (adjusted by the jets of the carbs).

That's just my opinion. I've never tried to make any major mods on these things. I just like to keep them running.

I mod my 350 cu. in. and it cost me enough money. I can't dump it in my boat too!..............:rofl: