Clutch math w/multiple changes

[benjamingvsu]

14 rtx

Last winter:

COTC,8DN, Soft start primary,9-1 wrap ( this was an accident I didn't realize until year end clutch disassemble) 8800+rpm, 101mph top speed achieved only once. Blew out tribhub last ride of year, not sure how long it took but that might have affected top speed at least that day.

Upcoming winter:
Studded with 120 studs
going with washers under the bolts to spread the secondary out; it was starting to wear where the sheaves rubbed together after 2 years of running with no bolts
Opened the airbox per Stingray on here.
Going back to original COTC primary spring & 6-1 wrap.
MBRP can
Primary clutch machined
4 wheel rear

Lots of variables so I'm looking for clutch advice - do you guys think I should go ahead and toss a gram or two of weight at it before I put the clutches back on? I don't know how to account for the studs, and have read conflicting reports on rpm gain from mbrp and airbox. Right now I have 8fp weights with 7 grams in tip and 2.44 in center. Also haven't decided which belt I want to run.

 

[RTX]

Not sure i can help but i run the 8fp weights in mine and can compare some notes, which might help
Last winter
Primary
8fp weights. 4.5 in tip .85 in center
Soft start spring with 3/1 mm shims
Secondary
Stock spring
Bdx progressive helix cant remember the cut thinking 46/40
Helix shimmed .080 set at 6/1
8dn belt
I run 3 studs per bar on a 129 ripsaw, whatever that works out to for studs. Cant remember it was a while back i studded it but i know its more than 120
Evo quiet can
4 wheel kit and 2 extra idlers on middle of the rails
No other mods
On a good day with the wind at my back i max out at 95 mph but i am hitting the revlimiter pretty solid.
I dont do a lot of top speed runs and because it was a bad snow year i was lazy and just left it as it was because i was sick of tinkering and just wanted to ride.

This year i added the evo stage 4 flash and stingray airbox mod. And ulmer header.
I know i am going to need more weight in the clutches. But it should be easier to clutch with the rev limiter increase.
Wondering where you found 7 gram weights for the tip?

You never stated what last years clutch weights were,
but 7 grams in the tip and 2.44 in center sounds like a ton of weight to me for just a can and airbox mod.

 

[benjamingvsu]

The weights in it now were before can and airbox. 7 gram was from mpi, but there are others cheaper I believe schmidt has them. Might even be able to use bolts, but I never played around with that. I loaded the tip so heavy because I was only overreving on top end runs. With the current set up I was pulling 88_9 rpm.

 

[RTX]

Fron what you are saying i would think adding weight will definately be neeeded
a gram is a step in the right direction. Probably gonna need more though

 

[sxr70001]

If you are adding studs you might lose some RPM's, but you are also doing the airbox mod which should gain a little so it might be a wash.

If if was me I would just leave it alone till I could ride it some see where I was at. But I understand if you just have to tinker.

 

[RTX]

If you are adding studs you might lose some RPM's, but you are also doing the airbox mod which should gain a little so it might be a wash.

If if was me I would just leave it alone till I could ride it some see where I was at. But I understand if you just have to tinker.

You might have missed it, but he has has also added an mbrp can along with the air box mod.
If it was the can and studs, or the airbox and studs, i would think you might be right about it being a wash,
But a can and airbox mod should make a pretty significant change.

I am kind of with you on leaving it alone and seeing how it runs, but it sounded like the OP wants his clutching finalized before the snow flys. (Thats going to be hard without actually running it)

 

[benjamingvsu]

I think you guys might be right,I might buy the 2 gram rivets I could put in the heel if I need it but may just wait and run it, that's an easy change.I haven't actually sent out he primary for the overdrive yet, do either of you have experience with that?

 

[RTX]

No i dont have any experience with having the clutches machined for overdrive.
Up to this point i have barely been able to break 95 mph. Im barely maxing out drive, no point in having overdrive lol
Seriously though, I have been trying to do things in stages in order to spread out the cost so it dont look so bad to the wife.
Even though she gives me very little grief about what i spend on sleds, theres no reason to stir the pot. Lol
Next year will be a new track, gearing and clutch machining.

 

[Curtis Chambers]

Put in I think it was yellow silver yellow spring 47 degree helix and drilled out centre rivet. Have seen 106 (road) and midrange is well improved. Mbrp can and header no difference.also had washers Put in and 8dn belt. Can hit 95 almost anytime. Nice and hard condition 101 pretty steady.