Track Tac

what clutch to use

T

taylorteamracing

Member
okay i have a 420 stroked to 440 (fresh) stg 4 head / flywheel/stroker crank/ billet rod/ 307 cam/ true full roller rockers/ 5/16 push rods/ 8" header/ crankcase evac syst/ making some where in the 40 hp range i changed tires to the new Hoosier treads for dirt and when i come out of the corner the noram star clutch slips and chatters half way down the straight away it runs the open outlaw 425lb class i am considering the Bully 1" Turbo, 4 Disc with the 14t driver the car is on a rail lol sticks very well what are the recommendations for this clutch
 
I personally. Would lock it up early .
High rpm stall is going to go through disc's . You got plenty of torque .
There may be a thread in the sprint section about it .
 
it does have a boat load of torque, this is the first disc clutch I will be running, and from what I read the 4 disc should fit the bill, I read some where on the vast innerweb the amount of hp and torque determines how many disc is needed, or the amount of disc is part of how much hp/torque its rated for, last night on the track coming out of the corner, it would lose power, (stop pulling) and rev up a bit, and when the kart increased speed the noram star would slow the rpm and lock back up, a person at the track was saying I needed a 2 disc, of course they had a used one (150.00), that's when I started researching it and found a two disc wouldn't last very long before burning the clutches, because its not rated for heavy/adult 35 plus hp I don't actually know haven't dealt with disc clutches before, so knowledge is power so I came here.
 
taylorteamracing said:
it does have a boat load of torque, this is the first disc clutch I will be running, and from what I read the 4 disc should fit the bill, I read some where on the vast innerweb the amount of hp and torque determines how many disc is needed, or the amount of disc is part of how much hp/torque its rated for, last night on the track coming out of the corner, it would lose power, (stop pulling) and rev up a bit, and when the kart increased speed the noram star would slow the rpm and lock back up, a person at the track was saying I needed a 2 disc, of course they had a used one (150.00), that's when I started researching it and found a two disc wouldn't last very long before burning the clutches, because its not rated for heavy/adult 35 plus hp I don't actually know haven't dealt with disc clutches before, so knowledge is power so I came here.
Click to expand...
That thing is pretty sweet man.
 
4 disc won't live either if you are running actual 40 CHP. You'll eat a set of $100 discs every night. Been there, done that.
Put the clutch back on a jackshaft and you can run a 2 disc. The torque curve on the big blocks is very flat between 3000-5500. I'd lock it up as early as you can 3500-ish.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
i ordered a bully 4 disc turbo clutch, i spoke with bully and they say this clutch will hold the motor but must be set up correctly to a early lock up and there is a whole different way these have to be maintained the clutch also dose not like part throttle or it be allowed to slip where it will build heat
 
I agree with Carlsonmotorsports about mounting it on a jackshaft. I have two modified big blocks, a Honda GX390 and a VC460 and have been racing them for a few years. Hanging the clutch directly on the driveshaft burns up the discs very quickly. You may get one or two track days out of them before they fail, and when the go kaboom it's usually in the feature. Its $80-100 per night to change them if you have not warped the floater discs as well.

The weight of the clutch mounted on the driveshaft will warp it at racing rpm and throw off ur chain alignment as well putting your drive gear, sprocket and chain at risk for damage. The initial buy-in for a jackshaft is a bit pricey, but you will be many dollars ahead and significantly less frustrated in the long run. What finally worked for me after trying almost every possible combination is a belt drive from the crank to the jackshaft and a 3/4 inch 4 disc Bully Turbo Clutch from the jackshaft to the rear sprocket. I also use 428 chain and Chautauqua sprockets. Bulletproof and the discs lasts for a half season.

Additionally I agree with the other posters on setting your clutch for the lowest possible stall speed. When a disc clutch is set at too high a stall speed the heat generated by disengaging, slipping and re-engaging multiple times in a race will significantly shorten the life of the clutch no matter how its mounted. This is my 2 cents based on my experience, your mileage may vary. Best wishes for success on this kart and keep us posted!
 
but what is confusing me is, if its on a jackshaft it would still be under the same punishment, just at a different rpm, and what would be the correct engine sprocket and driven gear, because now whatever that amount of torque is and the clutch still undergoes the engagement stall just at a different rpm
 
The jackshaft and drive chain/belt absorb some of the shock of each hit of the power stroke.
The jarring is what causes most of the issues.

Diesel pickups with manual transmissions suffer from the same issues. A dual mass flywheel is the factory's partial solution.
 
Last edited:
taylorteamracing said:
but what is confusing me is, if its on a jackshaft it would still be under the same punishment, just at a different rpm, and what would be the correct engine sprocket and driven gear, because now whatever that amount of torque is and the clutch still undergoes the engagement stall just at a different rpm
Click to expand...
The rotational forces will be on one axis when mounted to the j/s. When the clutch is mounted to the crankshaft the rotational forces are on two axis', the centrifugal force in the direction of the spin and the centrifugal force in the direction the of crank shaft warpage. Both forces are at right angles to each other and that multiplies stress on the moving parts.

The crank warpage at racing rpm with the heavy clutch mounted to the crankshaft will change the alignment of your clutch/chain/sprocket and risk damage to them.

Just like what 95 Shaw said. The belt drive from the crankshaft to the j/s absorbs some of the pulse shock from the combustion of the fuel and the motion of the piston. This puts considerably less stress on the clutch/chain/sprocket. The alignment of those parts is virtually unaffected at race rpm and enables the parts to last longer.
When compared to a small block clone, a two stroke or a MX engine you will see where the big block gets its nickname "The Paint Can Mixer".

As far as torque applied from the crankshaft to the clutch, that is very adjustable with a j/s by varying the size of the belt pulleys. You will have two ratios to deal with. The ratio from the crank to j/s and the ratio from the j/s to rear sprocket. You can increase or reduce the torque applied to the clutch by reducing or increasing (respectively) the ratio between the crank and j/s.
 
Last edited:
You must log in or register to reply here.
Back
Top