Vmax 700sx screams at 9400rpm??

W

wallyturcotte

New member
Joined
Feb 4, 2015
Messages
13
Location
Canada
Recently bought a 97 all original with 5500km replaced belt (89L) because of cracks, the machine is reving at around 8000rpm at half throttle, took shims out of the back of the secondary seemed to help a bit on lowering rpm but still reving over 9 what can I do to get the rpms down? Any info will help!
Thanks
 

I have 2 97 sx700 and both rev to that 9100-9200. This is something I was working on last year stick with the 89L They say it's a little softer and rev will be a little lower compared to the 8dn. Make sure clutches are clean and there are no bad parts. Nothing wrong with them. You will also need to figure out what you have for fly weights, rivets, rollers, springs, helix, ect.

This is my plan so far since my sleds are stock.
Primary clutch
fly weights 8ch Stock
Rivets 17.2 outer and 17.2 inner. (4.5 grams) (stock is 2.4 and 3.1 grams)
Rollers 15mm stock (May go to 14.5 if I still over rev)
Primary spring stock w s w
maybe 2 engagement shims (If engagement rpms are to low)

Secondary clutch
Secondary spring stock green set at 60
47 degree straight helix. Yamaha 8bv71 (45 degree straight is stock 8bv51)

Last year I did a 3.6 rivet outer and a 4.5 rivet inner with the stock helix at 60 degrees. My rpms where around 8700-8800. So this year I put in the 47 degree helix. I have not had a chance to ride it due to the lack of snow where I live. I also need to get the other rivet changed to 4.5 gram. I am thinking this should get me in that 8400-8600 which I could live with.
 
Thanks for the replys! This am I took the secondary back off and cleaned it top to bottom, checked everything over, now it's reving to 9100 to 9200rpm. Stock helix at 60. Talked to original owner and primary is all stock, has never been touched, (previously owned by senior) highly doubt he has ever had the machine wide open. Just bought a 1.25 ripsaw track I will be putting on this week, I'm thinking this will also change the way it revs at wot? Being heavier and more aggressive. Should I take the primary off and start by changing the weights or wait for the new track to be on and go from there? Or buy new springs for the primary and secondary? So confused!
 
check first what you have for rivets in the weights.You need to add heavier rivet to tip to get the rpm's down.If you are wrapped at 60 in the secondary and going full tilt,probably the belt is slipping in there as there is not much side pressure on the belt.Try a 70 wrap first and see what happens..but to tune for high revs is done in the primary clutch,the secondary you can fine tune a touch.See if everything in the primary is stock,give us the exact weights in there,the rivets if you can,roller size as well and we can go from there
 
Okay I'll pull the clutch apart tomorrow and let you know what is in there, just getting back into sledding after 12 years, so lost with some of these terms, what is a 70 wrap? Also will the rivets and rollers have markings or do I measure them with a micrometer?
 
you have numbered holes on your helix and outer secondary sheave..these are 1,3,6,9.Your secondary spring would be set at 3 and 3 (then twist the helix clockwise to line up the 3 studs)..this gives you a 60 wrap..for a 70 wrap you place spring ends in 1 and 6 holes,twist and line up studs and add the nuts and torque down..then you have a 70 wrap...the 2 and 6 hoes give you 80 wrap..so on and so on.
 
weights will have markings on them,rivets go by color and grams. You will need a gram scale to properly weigh each weigh with rivets to get them near all equal.But for now would like to see what you have in there,post some pics if you can would help.
 
9400rpm. damn thats high. Primary isnt binding or bringing up is it? I cant see weights groving out with such low mileage. Dont think previous owner would purposely clutch it that way either.
 
yeah he is running that engine about 1000 rpm to high...wouldn't want to be around when it explodes..lol.For that sled he should be at 8300 max.
 
Wouldn't weak springs cause low rpms? not high

Under target rpm.

Too heavy primary (drive) weights.
Too steep secondary (driven) helix angle.
Too low tension in secondary (driven) clutch.
Too tall gearing.

Over target rpm.

Too light of primary (drive) weights.
Too high tension in secondary (driven) clutch.
Too shallow secondary (driven) helix angle.
Too low gearing.
 
Just took the primary apart, took some pictures of what's in there, can't figure out how to post pics on my phone but if someone is willing I could e mail them to a kind fellow? Only writing I see is
08
0C the c looks more like a pacman
H
Spring is black with two white marks on it
 
The roller looks looks to be a 14.6 grooved
The rivits are both a gold color the middle rivet has a bigger head.
 
Cleaned primary clutch, set secondary to 70 was at 60 took for a test run and feels like clutch is getting hung up at 4000 then again at 2300 slight bog mid range, rpm is now at around 8800 8900
FML
 
first off , that sled was setup to run an 8ch belt ,very soft compound, you are now running 89L, you will over rev alittle , now you have a ripsaw track, more bite, try adjusting to 80* on sec. also your springs could be weak, replace the sec, and primary. and lastly put 14.5 mm rollers in the clutch! you do these things and you will be close to your rpm target.If not then change the rivets in your primary to heavier ones!
 
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