Supreme Exhaust Valves

[grandpaj]

I purchased a set of the ski-doo style valves. I live at 4800 ft in elevation. My sled is a stock M8 with slp single, clutched to run at 8100. After instalation it ran right 8050 and felt very good.
Went to Island Park for a few days and it would only run 7450. Adjusted the spring on the front of the valves as far out as I dared before the adjuster would just come out. Still could only get 7500. Put stock valves cable etc back in and 8100 again. any Ideas on how to get them to work so I can get rid of the burnt cable etc.
I'm sure the elevation had some effect on how they performed that is why I put that info in. I don't want to reclutch to get rpm as that would mean less weight in my primary and thet just means less hp in my book.
any info would be appreciated.

 

[NDM8]

I have the same problem 07 M8, put STM's in and lost rpm.

 

[diggerdown]

I don't really know anything about the stm valves but I do know pol. had problems with having too stiff of springs in for high elevation when they first came out with theirs. I would guess stm has the same issues.

 

[76FOMOCO]

just cut one coil off the bottom of the spring, this will give you more room to adjust the jam nut.

 

[Meatman]

why is less weight less hp? i'd be thinking on the opposite side....less weight to attain max hp at RPM....id check with stm for spring options first though....(cheaper )

 

[likinit2]

Being a Polaris guy that now has a M8. I have had the experience with this type of setup for the last 10 years. Sounds like the springs are waaaay too stiff. Cutting the spring will help but a much lighter spring rate is needed. I want to look into the same setup. Give us some feedback if you get it working right.

 

[bluebear]

I had them on my M8 big bore and they seemed to work fine at high and low elevation, but those were M7 valves. I would call STM.

 

[NDM8]

Thanks for the replies, will call supreme this week. Removed valves and they dont look like they are moving.

 

[tatorsalad]

springs

I used skidoo 800 springs and they work awsome on mine they are alot softer the 600ho are in between the stm ones and the skidoo 800 ho springs good luck

 

[ditch1000]

STM Exhaust Valves

Do the STM Valves improve the gas mileage on an 08 M1000???

 

[grandpaj]

Update

I called the guys at Powerquest and told them my problem. They ordered me some lighter springs, much lighter I will say. I put them in and started testing. In the shop I could see the one valve working the way I thought it should, but the other one didn't seem to funtion until you had the motor running about max rpms. So I switched sides with the valves just to eliminate the cylinder and the problem followed the valve. So after some more looking I tore the valve completly apart and lo and behold I found the one not working had a 1/16 hole in the front of the bellows. I took it to the power quest guys and they fixed it for me.
Got to ride it finally yesterday and I think it works great. Put 50 miles on and they are letting my rpms be what their suppose to be and the power is smooth and the mid range seems to me stronger than before. Hope to get some more seat time soon.