Jr champ bully setup

J

jayo48

Member
What would be the ideal set up for a bully 2 disk 6 spring clutch? Running jr champ, 360lbs, unrestricted clone.
 
Meant to add.... which springs and heights, and weights. Rebuilding mine, and was looking through the manual and it says red springs at .225" with one bolt for adult/jr stock. But looking through here I see some say different things.
 
My only concern was where does the clutch hold the engine on acceleration, at what rpm? If the settings you were given hold the engine at peak torque RPM, that's ideal. If not, adjust the clutch so it does!

If the clutch is holding the engine at peak torque, that force is transferred through the chain to the rear axle. With maximum torque at the rear axle, you have peak HP at the rear axle. During this period, while the clutch is slipping, the HP at the engine and the HP at the axle are different. Just look at the formula for HP; torqueXRPM/5252.1 = HP. Maximum HP at the axle should give you maximum acceleration.
 
We have also had alot of success on clone engine setups with black springs and double weight. I havent tried this setup on a Jr Champ, but the weight is the same as an adult clone (360).

Either combination with properly machined plates and the correct air gap are going to perform well
 
Red springs, one bolt in the outside of each weight lever. .240" spring height, .030" air gap.
That'll be close.
Only way to get it exact would be to know where the engine makes peak torque (most clone builders are very similar on this now) and to check your clutch against that (dyno, track, or bathroom scales as Alvin suggest.) I have my preferences, but I am pretty confident the settings I have provided will be a great starting point for you. :)



-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on FaceBook
29 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Thanks for the input. Really appreciate it. One other question regarding the weights. What exactly do they do?
 
jayo48 said:
Thanks for the input. Really appreciate it. One other question regarding the weights. What exactly do they do?
Click to expand...

A heavier lever will make a clutch "snap" harder and quicker, in theory.

But this also has to be set with the correct spring weight. A light spring with heavy weight will snap too hard and cause a chatter...a light lever with a heavy spring will cause a chatter.

The spring/weight combination works in tandem. Red springs are pretty universal, which is why its a standard setup that covers 80% of applications. There is some performance to be found in the right spring/weight combo for given weight and engine classes.
 
CarlsonMotorsports said:
Red springs, one bolt in the outside of each weight lever. .240" spring height, .030" air gap.
That'll be close.
Only way to get it exact would be to know where the engine makes peak torque (most clone builders are very similar on this now) and to check your clutch against that (dyno, track, or bathroom scales as Alvin suggest.) I have my preferences, but I am pretty confident the settings I have provided will be a great starting point for you. :)
Click to expand...
Really good advice, pay particular attention to the parts I have marked in bold print.
 
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