drivetrain upgade. overreving engine

D

Dennis

Banned
Hi.
I made a drivetrain upgrade on my vmax 750 93' this spring. with house , jackshaft, and secondary from a 800.
i also put a sc-10 3 suspension from a renegade o6' under it. brackets loweret in the back for clearence and mounted a back country 1.75 track. and 8 tooth exo. drivers.
The clutch is standard 93'

The engine revs to 8600 in WOT. and it seems very slow. i know that 13" suspension and 1.75 track takes a lot of top speed but i dont think i can get it up to more than 130-140 KM/h. The gearing is lower now, but i also put on 8 tooth drivers witch gives higher gearing. I have owned a 750 and a couple of 800's in the past and got pretty god experience on working with them, but i never messed around with clutching before, because it never had been a issue before.

My question is:
Do i need to change to 8bu weights and spring too?

I think i want to try yammiegods clutch setup next winter. But i have searched for a setup for a 750 with 800 driveline, and i can't find anything.
Is it a 800 setup i am going after?

Is there anyone here who can help me out with this?
 

Actually going from a stock 9T driver to a smaller 8T driver will give you a deeper ratio, not higher gearing as posted. Your close on the rpm as 8600 rpm's isn't really that bad for a back country rider, although 8350 is optimum...your in the ballpark. Before you change too much in clutching, what gearing do you have in the sled? What number of teeth on top gear and bottom gear, with that info given I can calculate your "max" mph. Keep in mind that it takes "lots" of horsepower to turn a 1.75" paddle track as compared to a .750" lug height, plus the added suspension travel and the sharper approach angle on the front will cut speed greatly. So you may not be as far off as you think with all factors taken into consideration. Also a 1.75" track could suck up as much as (10 "track" horsepower), which is equivelent to almost 20 crank horsepower being robbed. Anyways, hopefully this helps you out!

EDIT!!! Also about your question on changing the primary spring/ weight combo, what are you attempting to gain? Are you trying to lower that 8600 rpm's, more engagement, ect ect, LOL! For every change made on the primary it will have a reverse effect on the secondary and vise versa. Maybe just add more weight to the flyweights, just some .02 for ya.

Also for many other fellow Vmax-4 owners, I realize 8BU's weights are a very popular weight on our Vmax-4's and other Yamaha's, but are harder to come by these days. For those willing to make the investment you got to try the Supreme Tool & Machine "Super Tip" weights, they are awesome! The Yamaha version has an identical profile and ramp curvature to an 8BU. They are completely easy to add weight with 3 different areas to load and eliminates messing around with lead rivets and ect. It took me awhile to convince Curt Wald to give them a try as he loves the 8BU's but he too see's the ease with the Super Tips. Just wanted to pass this tidbit on seeing the talk of weights always comes up on hear.
 
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Thanks for the reply.
Sorry about the higher/lower gearing swap. i always forget what term to use. I don't remember exactly how much but the new topgear was 2 tooth bigger i think,and on the button side ecual smaller. if i remember correct the old one was stock, 93 and the new chain from a stock 95.
So My theory was that the new gearing would give more topspeed, but the 8 tooth would level it down to about the same gearing to the track.
But i am olso not aware of how much 2 tooth in the top versus 8 tooth drivers will be in difference so maybe my theory is way of.

About the track.
I know i will loose speed with bigger track. i normally uses a 1.25 track on my snowmobiles, because of the many mountains uphere. and i usually get about 160 at topspeed on the 1.25. so i did not imagine that the 1.75 would take so much more topspeed.

I havent been riding since 2002. before that i was driving 2000-3000 km a year for many years mostly on the 800. the thumb were itching more and more for each year and last winter i got a nice offer on the 750 so i decided to make it as i always wanted, with the suspension and the track.

But once i tried it out the first time up the hills i was disapointed. there is no pull when you hammer the throttle. from 0 to 20 is lifted skiis and big smile, but from there it lacks speed. Alot.
the revs is pretty constant. maybe 8650.

About the weights.
I do have a set of 8bu weights, but i just dont have the spring.
Is it worth an effort to get the spring and try it out?(got the tall cover too)
And yes, i want to bring the revs dovn a bit. there is a lot of WOT when climbing mountains

I hope not that i have to live with 130 km. at topspeed. Then my wife would overtake me with a phazer 485 that i also is bringing back to life, on the lakes. that wouldnt be very funny. exept for her.

And a little respeckt for you at the end here. when the needle i stuck on the button at the speedometer on the lakes, on the standard track i am full of adrenalin. i cant imagine how it would be with your turbo machine.
 
I will get the exact numbers on old and new gearing for you tomorrow i you would calculate expected topspeed for me.
 
a nother weight that has the exact profile as the 8bu weights is smidt bros adjustable weights for the 2010 nytro they come in at the same weight according 2 my gram scale and they are ajustable on the toe, heel with little bolts and shims plus allen head screws for the heel. with ur 8 inch drivers u will lose lots of speed, if i were me i,d roll that chain case so u can put ur 9 in drivers back in.
 
Dennis said:
I will get the exact numbers on old and new gearing for you tomorrow i you would calculate expected topspeed for me.
Click to expand...

Sounds good, when you get around to it PM me your gearing setup and I can give you the the mph @ 1:1 @ 8350 and 8600 rpms so you know where your at. You'll be just fine with the 8 tooth drivers for the type of riding your doing, your just going to loose some h.p and mph with the combo your running, its a give and take.
 
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