[richeyb3]

Just rebuilt 2004 Yam SX Viper Mtn and during breakin noticed that at wide open throttle I would get 9,100 RPM. Checking the manual Specs it says that the engines Max horse power r/min is 8,500 r/min Just wondering if I'm over speeding the engine or if once it is at 8,500 r/min I'm not getting any more horspower? Or what??
Richey

 

[yamadad4]

you are correct. max power on your sled is reached at about 84-8500 rpm. anything above that is overworking the motor unnessecarily with no performance gain.

time to do some clutch tuning.

 

[richeyb3]

you are correct. max power on your sled is reached at about 84-8500 rpm. anything above that is overworking the motor unnessecarily with no performance gain.

time to do some clutch tuning.

Thanks I'm in the books reading, will this take parts or just re-adjusting what I have?
Richey

 

[yamadad4]

you will need parts. nothing major, just tuning rivets. thats an endeavor in itself.

based on your description, i would say you need to loose about 2 grams of weight from the tip.

rule of thumb, but not always consistent, 1g=300 rpm. unfortunately yamaha did not make this an easy change

did you regear during the rebuild? pipes or stock exhaust?

 

[richeyb3]

The machine has had pipes for years and clutch and rpms all seem to be fine for the past 5 years before it seized...

Only thing I have done is rebuild the engine... same weights and clutch etc.. new belt

Richey

 

[yamadad4]

what brand of pipes? hopefully slp's. certain manufacturers require different rpms ranges.

probably just an end result of all the new horsepower you created by freshening up and correcting the motor.

good job. see what you did? you created more work for yourself. ha,ha, joking.

 

[yamadad4]

you will need parts. nothing major, just tuning rivets. thats an endeavor in itself.

based on your description, i would say you need to loose about 2 grams of weight from the tip.

rule of thumb, but not always consistent, 1g=300 rpm. unfortunately yamaha did not make this an easy change

did you regear during the rebuild? pipes or stock exhaust?

i would like to clarify a mistake on this post. due to the overwhelming number of messages and activity tonight, what i should have said in regards to the tip weight should have read "ADD 2 GRAMS" of tip weight. all other statements are still relevant to the best of my knowledge. sorry for any confusion.


for those that may be following, anytime horsepower increases, the proof is usually in the calibration of the clutches. if you make any alterations to your sleds engine(even a rebuild) and suddenly show an overrev, you have made power somewhere. proof is in the tachometer.