Clutch help!

D

Daniel5304

Member
I have a Jammer 2 disc 6 spring clutch. I want it to engage at 2800 rpm for box stock predator class. It is currently set up with (Bully) black springs @ .275, weights on the inside, and the air gap is .040 (iirc)

What is the best way to check what rpm it’s actually engaging at with it setup this way? Is there a way to set it up by trial and error that DOES NOT burn the clutch up? Does it sound like I’m in the general ballpark with it setup the way it is, or am I way off?

Side note - my reason for running bully springs is because jammer bob is a very hard man to reach. Got him on the phone once, but it was a Friday around 5, so he asked me to call back the following Monday. Since then, his grandson answers every time and says he’ll have him call me back, so I gave up.
 
Bathroom scale between the front of your kart and a strong wall. Only takes 2 or 3 seconds. The highest reading on the scale means the highest amount of torque going to the rear wheels. The highest torque at the rear wheels means the most horsepower at the rear wheels.

I can hear you saying "that might burn up the clutch", but it won't, not if you do a right.
 
Thats a place too start .
If theres holes on the outside might add bolts in them .
You have a tach ?
Set it on the ground .
Watch it when it starts to move is where its engaging .
Adjust from there .

The scale method will also work .
Just dont hold the thing full throttle for minutes at a time . Allow time too cool between adjustment
 
flattop1 said:
Thats a place too start .
If theres holes on the outside might add bolts in them .
You have a tach ?
Set it on the ground .
Watch it when it starts to move is where its engaging .
Adjust from there .

The scale method will also work .
Just dont hold the thing full throttle for minutes at a time . Allow time too cool between adjustment
Click to expand...

Yes, I have a Mychron3. Seems like the reading on it jumps around a bit though. So I’m gathering that I should try to set It for 2800 rpm with the tach, and then do the scale method to dial it in exact?
 
alvin l nunley said:
Bathroom scale between the front of your kart and a strong wall. Only takes 2 or 3 seconds. The highest reading on the scale means the highest amount of torque going to the rear wheels. The highest torque at the rear wheels means the most horsepower at the rear wheels.
Click to expand...

Just to be clear: if the kart is not moving, there is no horsepower being produced at the rear wheels. Only torque (a static force).

PM
 
Daniel5304 said:
Yes, I have a Mychron3. Seems like the reading on it jumps around a bit though. So I’m gathering that I should try to set It for 2800 rpm with the tach, and then do the scale method to dial it in exact?
Click to expand...
Thats a big question .
Will your nose hold up ? That would be a concern .
First figure where its at now . Write it down . Do a scale test . Then make the change . Document that .Turn the adjusters in 1/2 turn too raise rpm . Do a test . Check your results .
Honestly i would set it with the tach . Then add 1/2 turn (per time) in too raise rpm at the track or at home . If i felt it was needed . Its not going too be a race winning adjustment .
 
flattop1 said:
Thats a big question .
Will your nose hold up ? That would be a concern .
First figure where its at now . Write it down . Do a scale test . Then make the change . Document that .Turn the adjusters in 1/2 turn too raise rpm . Do a test . Check your results .
Honestly i would set it with the tach . Then add 1/2 turn (per time) in too raise rpm at the track or at home . If i felt it was needed . Its not going too be a race winning adjustment .
Click to expand...
I left it on the stand and let it idle a while to warm up. Then, I just held the back tire with my left hand tightly (so I could feel it try to spin) and ran the hand throttle up slowly on the motor with my right hand, while watching the tach. Looks to be engaging around 2500 rpm. I’m going to do as you suggested and turn the springs in half a turn, then try again. I’m still tempted to try the scale method to dial it in even better, but I think I’ll wait for now.
 
alvin l nunley said:
Bathroom scale between the front of your kart and a strong wall. Only takes 2 or 3 seconds. The highest reading on the scale means the highest amount of torque going to the rear wheels. The highest torque at the rear wheels means the most horsepower at the rear wheels.

I can hear you saying "that might burn up the clutch", but it won't, not if you do a right.
Click to expand...
Can someone please explain into detail on how to do this scale test?? I have been playing around with a 2 disc 4 spring clutch predator 212 it’s slightly built but still stock cam and piston and stuff and I have been just setting it by my tach. It’s not a bully clutch it is an old “rockstar” clutch but it’s almost identical to a bully clutch. Other then a few things. But I run bully springs and friction disc. I am planning on getting a bully clutch but I want to get setting them and all that good stuff down before I get a expensive clutch I don’t want to fry parts lol this is my first racing kart and disc clutch.
 
alvin l nunley said:
In order to add details, first tell me what you don't understand.
Click to expand...
Just need a little more detail, like my engine hasn’t ever been dynoed so I don’t know what the torque or anything is does that matter? And I just put a scale between my front bumper/nerf bar and press the gas till the clutch engages? Is there a amount of time I should do it for? I get not to do it for to long so I don’t burn up the clutch. Honestly I’m just amazed that it actually works lol I need to go get a scale cause I think the only one I have at home is glass lol
 
You need a spring scale . And probably a helper .
Once your topped out thats it , test over .
Make whatever change , do it again .
If its more you improved . If its less , reset then go the other way .
Test again till it tops out.
 
DrewSkii said:
Can someone please explain into detail on how to do this scale test?? I have been playing around with a 2 disc 4 spring clutch predator 212 it’s slightly built but still stock cam and piston and stuff and I have been just setting it by my tach. It’s not a bully clutch it is an old “rockstar” clutch but it’s almost identical to a bully clutch. Other then a few things. But I run bully springs and friction disc. I am planning on getting a bully clutch but I want to get setting them and all that good stuff down before I get a expensive clutch I don’t want to fry parts lol this is my first racing kart and disc clutch.
Click to expand...

There is no need to do the “scale” test unless you want to burn up the clutch, punch a hole in your drywall, or bang up your body.

Based on your engine description, you’ll want the clutch hitting around 3000 RPM.

Black bully springs, .225 spring height, double weighted levers should get you close. Fine tune from there.
 
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