overdrive sheave


I machined "0.100" off the center flange on the helix to get overdrive per bruce's recommendation at cbperformance ( one of a bunch of clutchign changes i made at once.
not sure if it is shifting out further or not. never checked it ,but if it does, seems a lot cheaper than an aftermarket sheave


just another suggestion
Ramb
 
I would not invest the money in them.............differnt angle sheaves on the sides of the belt results in black burnt rubber on the clutch face, been there done that.
 
In order for you to fully clutch out, you need to purchase the overdrive sheeve and machine .080" off the inside of the helix on the secondary. The angle difference between the stock and the overdrive is very minimal and we have yet to have any problems with premature belt wear running our overdrive. As long as you break in your belt using the overdrive (aka, run a new belt with the overdrive) the belt will be broken in with the correct angle for the overdrive sheeve and there should not be any problems. Make sure you put the belt on the same way everytime too.

I personaly have not had any problems with burning belt rubber on my clutches.
 
this srx had a speed sheave in it, but it was not a drag racer
 
full overdrive isnt nearly as efficent as closer to 1:1 rastio in a clutch anyways, you can easily set up a srx to run that mph without a speed sheave, the further into overdrive you go the more bending of the belt, thus a loss in efficency, results in a loss of power transmitted to the jackshaft/track/ground.............to each his own, its your money spend it as you feel the need to. I have used them before and they are just snake oil in my opinion.
 
mrviper700 said:
full overdrive isnt nearly as efficent as closer to 1:1 rastio in a clutch anyways, you can easily set up a srx to run that mph without a speed sheave, the further into overdrive you go the more bending of the belt, thus a loss in efficency, results in a loss of power transmitted to the jackshaft/track/ground.............to each his own, its your money spend it as you feel the need to. I have used them before and they are just snake oil in my opinion.
Click to expand...

mr. viper's way to a 1-1 ratio is the best way to go, ben there done that too. i had with what i had to work with. the owner of the sled did not want to take the speed sheve off since he just spent $150.00 with hauck.
i guess there is a coulple of ways to skin a snake!!
 
you can look at it eaither way i guess.
an overdrive setup gives you a wider gear ratio range overall ( but maybe not as efficient at full shiftout.

you could change the gearing to get the same final ratio and possibly same or more speed, but your initial launch ratio would be less .

dyno testing would be nice to see
or just simply test/test/test to see what an overdrive setup does 0 to 125 vs. a gear change. keep ing other things constant.

ramb
 
i had the primary shaved i think it was 30 thousandths but cant remember and ran 21/38 gearing and got better speed. this keeps the angles the same but lets the clutches close closer to get full shift.
 
Primary machining

With the stock setup it seems to me that the primary clutch shifts out completely and bottoms out. This full shift limits futher belt advance. If you remove the spring in the primary and move the clutch to full shift and at the same time put a belt around the clutch there is plenty of travel available for more shift. Can anyone report they have found speed by machining the bottom area of both insides of the sheaths. Would seem to me .04 to .05 on the inside sheath and also the movable sheath should gain some MPH. I tried long ago the secondary trick removing .100 thousanths from the helix only to find out through testing the primary was bottoming out. The helix trick does not work without primary machining. At least thats my findings. Anyone else. I have dicussed this topic before only to find no one else testing the machining of the primary.
 
well ill follow the been there done that from mr viper and keep my original sheave lolll
 
Mac,

You are correct you must do both sides to make it work. The 1/2 degree angle gives you a better grip on the belt. I run over drive on all may sled with a gain of about 2 to 3 mph. I also run it on my Apex with 275 hp with nos no burnt belt. Maybe I am just lucky.
Bruce
 
o.d. works great.
i have spent countless hours testing with o.d. on timers & radar. i have never used a aftermarket o.d. sheave. i machine the primary & run an ad-vantage roller secondary ( never tried it with a button clutch ). the o.d. allows a wider selection of ratios between engagement & full shift. it's like comparing a 6 speed transmission to a 4 speed.

bob
 
Please help! - Buffalo Bob

Come on Bob please provide details. What parts are machined and how much? Did you machine the pocket in the helix where the spring rests? Does the belt now climb all the way to the top of the clutch? Any other details I'm missing please do tell.
Thanks Bob --mac--
 
true the surface of fixed & movable sheaves.
with sheaves seperated start by cutting.020 off each side ( flat ). cut down the split collars an equal amount ( in this case .040 - keeps neutral the same ). keep doing this until upon assembly you get the belt to ride even with the top of the primary when fully shifted out.
i am not usung a button secondary so you will have to figure that out yourself. this will change the offset so you need to shim the secondary on the shaft & make sure @ full shift you are not hitting the chassis.
yamaha clutches are 5% o.d.. this will give you 13% - 15%.
gear down 2 teeth on top & you will be close to same mph you started with but stronger bottom end & midrange.
i also reccommend a IS clutch gaurd - bender sells them & they rivet to the inside of the yamaha clutch gaurd.

bob
 
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