Clutching on the cheap

[sparky72]

Ok. So. With winter on its way (we all hope) I'm starting to think about getting my sled ready for the upcoming season. I have the COTC with the 4.5g's in the tip. My problem is on a long straight on hard pack or a real nice price of trail I'm tapping my rev limiter still. After looking at the Yamaha chart I'm wondering which rivet anyone would suggest to put in the second hole? I'm totally stock except for clutch. Also, my GWG engages my clutch at approx 3500 rpm still with 4 shims. Suggestion?

 

[stingray719]

Ok. So. With winter on its way (we all hope) I'm starting to think about getting my sled ready for the upcoming season. I have the COTC with the 4.5g's in the tip. My problem is on a long straight on hard pack or a real nice price of trail I'm tapping my rev limiter still. After looking at the Yamaha chart I'm wondering which rivet anyone would suggest to put in the second hole? I'm totally stock except for clutch. Also, my GWG engages my clutch at approx 3500 rpm still with 4 shims. Suggestion?

What are your secondary settings? Also, with the primary clutch cover off (and the belt off) can you push the clutch sheaves in and out all the way by hand easily?

 

[fasteddie15x]

you can get heavier rivets from hauck powersports in Rice Lake Wisconsin, just google them and you will find there website. They have 5.0 5.5 and 5.9 gram rivets listed, and of course lighter rivets. I was trying different clutching last year and also hit the rev limiter with the COTC set up with 4.5 in the tip. As you get more miles on your sled and if it has mods, you might have to add more weight to the tip. I did not have the opportunity to try it with more weight in the tip.

 

[sparky72]

Yes, it is loose. I put it together just after the 500 mile break in, and has done it since then, go on a trip, add weight, go on a trip, add weight. It now has 2000 miles on it. Secondary is stock except I shimmed the helix and am running an 8DN (with washers). It doesn't do it all the time, only when the trails are ssuuuwweeet.....

 

[shagman]

Yes, it is loose. I put it together just after the 500 mile break in, and has done it since then, go on a trip, add weight, go on a trip, add weight. It now has 2000 miles on it. Secondary is stock except I shimmed the helix and am running an 8DN (with washers). It doesn't do it all the time, only when the trails are ssuuuwweeet.....

This is where I was before I added my turbo. Once i added in the middle it smoothed ot the rpm spikes. I had abourt 2800 miles then.
8FP 4.7g tip, 3.2g middle

 

[stingray719]

As these sleds run better and better after they get some miles who knows where it will level out at?

 

[stingray719]

You might try the OSP magnetic weights with Barn Of Parts soft start spring and 4mm to 6mm primary spring shims. OSP weights are not flat but a good second choice to 8FP weights if you want adjustable. Please note that the green white green spring that comes with the OSP kit works very well, but I prefer the soft start spring to get a better take off from start. Either spring will do the job.

http://www.ospracingparts.com/yamaha-sr-viper-clutch-weight-kit/

http://www.barnofparts.com/Soft-Start-Clutching.html

https://thunderproducts.com/shop/clutch-spring-glide-washer-kit/

 

[Lynvingen]

XTX 153" 2.6 powerclaw 21/41 gearing, Hurricane stage 3, stroker kit.
Stock 43 helix and pink secundary spring at 70 *
8 JP
Supertip 60y
Heel 14 g tungsten
Mid 5 washers
Tip 5 washers
Dalton green spring
Just a few test runs at 14 psi.... KABOOM! My belt was gone. Wery hot clutches. 10 min after i could hold the secundary, but the primary was hotter.
Too hevy weights?

 

[cannondale27]

Not too many Turbo guys have had any luck with stock 8JP.

 

[Studroes144]

Here's the 2nd blown 8jp belt from my turbo running half the boost you are. They only lasted 200 miles for me. After the second one blew I put 800 miles on an 8dn and worked good, I was hard on it and it showed signs of wear, but at 200 hp or more I'm very pleased to get 800 miles out of a belt that I can get for $50 brand new.

 

[Lynvingen]

I will try DN belt. Mine was separated right off. I also was at limiter a few times from standing still. I think that the primary could not hold the belt. Any suggestions for setup? Springs and helix?

 

[Studroes144]

I will try DN belt. Mine was separated right off. I also was at limiter a few times from standing still. I think that the primary could not hold the belt. Any suggestions for setup? Springs and helix?

Was this just a pull the sled out of the garage and run it type thing? I personally think that one of the biggest things that's overlooked with belt issues is "when the belt blew". Meaning, were you on an actual ride where the engine, belt and clutches were all at normal operating temps? If you pull the sled out with a cold belt and cold clutches, first bad thing that's gonna happen is the belt will slip like crazy, and like you mentioned you're gonna be right on the rev limiter and with the super hard 8jp if it gets slipped enough it'll glaze over and really lose grip. With everything slipping bad it's gonna get very hot and eventually blow a belt, and at 14 pounds it'll probably be bad. I've seen a guy with a brand new cat turbo that was running around 260 hp go out and blow 2 belts in less than 5 minutes..my theory on the cause, he pulled the sled off the trailer, got the engine warmed up and pinned it the whole length of the field, half way across, BANG!!, put a new belt on, ride around for about a minute, another wide open run, BANG!!..he finally took it easy after he wasted $400 in 2 miles. I've also seen guys with 280hp cat turbos get a full season of 2000 miles or more on one belt with no issues, the difference, when they take they're sleds out of the garage for a ride they ride for at least 5 minutes before holding it wide open for much difference, a cold belt and cold clutches are a bad combo when u have a lot of hp and just go out and pin it. So before you go making changes I'd suggest putting an 8dn on and just riding it and get some seat time with everything up to operating temp and then see how the sled reacts.

 

[stingray719]

I did a "clutching on the cheap" turbo test with 8FS weights that came in a Nytro mountain. Worked great at altitude but for low level a guy would have to get VERY heavy rivets like the brass 7 gram MPI rivets to get the weights heavy enough. So I went with OSP magnetic weights and Barn Of Parts soft start spring with 6mm worth of primary spring shims and couldn't be happier. For aftermarket weights you might want to start a new Supertip thread, as more people with your weights may see it.

 

[cannondale27]

I think with 8jp being shorter and alot of power the belt limits potential travel of clutches and bang. Most NA sleds will never reach that point.

 

[Blue Dave]

My sled must be gaining some HP as it breaks in because I am now sometimes bumping against the rev limiter on top end.

I have the COTC set-up with 3.6G rivets in the outer holes of the 8FP weights.

Should I replace the 3.6G rivets with the 4.5G rivets in the outer holes or should I add some weight to the middle holes? If so, how much?

Thanks in advance for the help.