RPM question......

[stingray719]

SO if Yamaha is putting what looks like a variant of the Vector engine in the new SXS side by side and it redlines at 10,500 why are we restricted to 9200?

 

[4StrokeAddict]

Number of valves?

 

[NOS-PRO]

Primary clutch rpm is the concern. They say you shouldn't rev more than 9,500 with primary clutch with stock cover. The reason the Apex and RX1 can rev more is because of the gear reduction.

I have this 911 cover on my sled now so I am safe to 12,000 rpms. Not only that but the 911 cover allows the clutch to move more free, has a larger bushing, strengthens the towers and you are able to adjust the primary so the clutch doesn't slam against the belt.

 

[yamahajohnson220]

Id say Nos-pro nailed it. Except he forgot to mention the phazer engine also.

 

[NOS-PRO]

yamahajohnson220 is correct, I did leave out the phazer.... I even have a phazer..... (brainfart today)

 

[4StrokeAddict]

Primary clutch rpm is the concern. They say you shouldn't rev more than 9,500 with primary clutch with stock cover. The reason the Apex and RX1 can rev more is because of the gear reduction.

I have this 911 cover on my sled now so I am safe to 12,000 rpms. Not only that but the 911 cover allows the clutch to move more free, has a larger bushing, strengthens the towers and you are able to adjust the primary so the clutch doesn't slam against the belt.

Are you running higher revs? If so, what is your limiter set to? If memory serves, you are turbo-ed... I'm guessing this is how you are getting higher reves? If not, how much can you get out of this engine stock with a reprogram?

 

[shagman]

Are you running higher revs? If so, what is your limiter set to? If memory serves, you are turbo-ed... I'm guessing this is how you are getting higher reves? If not, how much can you get out of this engine stock with a reprogram?

Nos-Pro is not running a turbo. i am running and OSP turbo and just ordered the ignition module and plan to run 9400 rpm while Nos-Pro is running that now with header muffler and air box. I will let you know how it works when i run asphalt on the 13th.

 

[stone88]

Nos-Pro is not running a turbo. i am running and OSP turbo and just ordered the ignition module and plan to run 9400 rpm while Nos-Pro is running that now with header muffler and air box. I will let you know how it works when i run asphalt on the 13th.

The rev X tend on the Viper is not working the way its supposed to, I ran it up to 9200 one weekend then the next weekend it was bouncing off the rev limiter at 8900 rpm then the next time out 9350 then the following weekend 8900 again so I took the rev X tend off and it now goes to 9150 every run and is much faster. I don't spin my engine at those rpm's just at the end of the run when it goes into overdrive. I spin my engine at 8600-8900 through the run but that's what makes my sled work yours may differ.

 

[shagman]

The rev X tend on the Viper is not working the way its supposed to, I ran it up to 9200 one weekend then the next weekend it was bouncing off the rev limiter at 8900 rpm then the next time out 9350 then the following weekend 8900 again so I took the rev X tend off and it now goes to 9150 every run and is much faster. I don't spin my engine at those rpm's just at the end of the run when it goes into overdrive. I spin my engine at 8600-8900 through the run but that's what makes my sled work yours may differ.

Are you running a turbo. I had heard that some turbo sleds are having trouble with Rev-extend. It seems to be fine on Nos-pro's sled ( non turbo)



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[stone88]

Are you running a turbo. I had heard that some turbo sleds are having trouble with Rev-extend. It seems to be fine on Nos-pro's sled ( non turbo)



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Yes it started out as an MCX low boost kit on it then I added an intercooler and PCV with bigger injectors and an in tank large volume fuel pump and regulator all on a stock motor running straight C-12 and it has run 8.91 @ 145 with me on it Im 250 plus suited

 

[stingray719]

View attachment 109584
Primary clutch rpm is the concern. They say you shouldn't rev more than 9,500 with primary clutch with stock cover. The reason the Apex and RX1 can rev more is because of the gear reduction.

I have this 911 cover on my sled now so I am safe to 12,000 rpms. Not only that but the 911 cover allows the clutch to move more free, has a larger bushing, strengthens the towers and you are able to adjust the primary so the clutch doesn't slam against the belt.

Yes but the Viper engine could also have gear reduction, my question was tongue in cheek as we know Yamaha overbuilds so you can't damage there engines. Look how the R1 dropped close to half its horsepower when it was put in the RX1.

Our Viper engines could be over 200 horsepower from the factory if they wanted too.

 

[cannondale27]

Don't forget we don't have Titanium valves. I agree though no reason other than clutch and longevity that our motors are so limited. Now as for power it would be nice to either have peak at 8500 rpm and leave rev limiter alone or have peak where it is now right around 9100 rpm and have over rev to about 9800 rpm. I may or may not increase the rev limit. Would prefer way more power at 8500. But if I do I would expect some decreased longevity. The gear reduction in Phazer and Apex is a mechanical buffer that makes it easier on the motor to drive a sled at high rpm for a long time. No street bike sees Rpms like a sled unless raced. A better comparison would be to the watercraft. As for engine life it seems to me other than keeping oil in and stator,coil and other electrical issues these Yamaha motors last 5 times longer than most 2strokes so maybe killing a year or two is livable! This is one of those things that maybe should not be talked about especially under warranty. I have heard with Dynojet your serial number is required. Call me paranoid but WHY?

 

[NOS-PRO]

Yes but the Viper engine could also have gear reduction, my question was tongue in cheek as we know Yamaha overbuilds so you can't damage there engines. Look how the R1 dropped close to half its horsepower when it was put in the RX1.

Our Viper engines could be over 200 horsepower from the factory if they wanted too.

The viper clutch is driven right off of the crank so there is no gear reduction. Could it have like the Apex and RX1? Sure, but I don't think yamaha is going to add that option....LOL.

That is why the RX1 dropped it's horsower because of the gear reduction to spin the clutch at 8,900 and the engine at 11,000 and not 13,000 because the clutch would be flying at 10,700 and would not last.

 

[NOS-PRO]

Are you running higher revs? If so, what is your limiter set to? If memory serves, you are turbo-ed... I'm guessing this is how you are getting higher reves? If not, how much can you get out of this engine stock with a reprogram?

Just like Shagman said, I am not running a turbo and the higher revs with the ignition module is working great! I have no problems seeing 9,480 - 9,520 on a 1/4 mile pass now. Rev limiter is set at 9,600 right now.

When the performance flash comes out from Evo, I have told them that I would like to see the rev limiter raised to 9,400 at least because the power is definitely building past 9,150 or 9,250 (2014 & 2015 rev limiter).

 

[mtotguy]

these Yamaha motors last 5 times longer than most 2strokes so maybe killing a year or two is livable!
That's the conventional wisdom these days. But I've had a lot of two stroke snowmobiles and I've never worn out a modern one (1990's up). I've burned down a few. Always Arctic Cats. I've had two SX700's with over 10 thousand miles on them and never had them apart. I had a Polaris XLT. The speedo quit working 15 years ago at 9000 miles. A friend of mine is still riding that sled. I have a friend with an F700 who just rebuilt the motor after 15000 miles. Now on the other hand, my CR250F needs valves and a piston every season. I think this whole 4 stroke longevity thing is a bit overrated.