New clutch engagement around 3300

ggodwin

Member
I just got a new clutch that is currently engaging around 3300 rpms.

Can someone she some light on the reasoning behind different engagement rpms?

I assuming track size, class etc other variables apply.

We’re on intetermediate track sizes all the way down to a 1/10 mile short track running clone motors. Any suggestions?
 

alvin l nunley

Premium User
Picture coming out of a turn, you're at full throttle, the clutch is holding the engine at a given RPM. It's at that RPM because the clutch is absorbing all of the torque the engine is producing, give or take some because of the heat it's producing. That torque is transferred through the chain to the axle. At this point, it's possible to calculate the horsepower being produced at the axle. More or less torque, more or less HP. So if the clutch is holding the engine at peak torque, you have peak torque at the axle, which means you have peak HP at the axle. Torque X RPM/5252.1 = HP

So, if you know the RPM at which your engine reaches peak torque, you know where you want your clutch to be slipping.
 

paulkish

old fart
Assuming you're correct on a longer track: ....

Generally, when you put more gear on going to the smaller track, you tweak the clutch a little making it engage a little sooner.
With a disk clutch, the tweak maybe only a 1/8 to 1/4 turn tighter on each screw.

Then when you go back to the larger track even if you forget to do anything to the clutch your probably ok.
You're probably ok because of wear and tear on the clutch making the little bit of tweaking ok.

IMHO, forget what you were told in post #2 he has no clue about the question you asked and is just rambling with garbage as far as answering your question.

We did that all the time going from 1/5 to small 1/8 and beyond tweaking going to the smaller track seldom had to back off the tweak when going to the larger track.
By the time it made any difference the clutch was worn and in need of new disks.

It was like sure if I went 1/4 turn in the back it off when going to a larger track was only not quite a 1/4.
As the clutch wears and generally when you go to a shorter track you need to tighten the clutch up a bit for the additional gearring and wear.
Why we needed a bit more on the shorter track, we didn't really car way, just knew it needed it and if it didn't get it, wasn't as good until the clutch needed to be redone.

I'm thinking about when we ran our stuff hard, like two tracks on Saturday and one on Friday and maybe Sunday too, each weekend.

.
 
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ggodwin

Member
Let me rephrase my question.

It’s a Bully 2-disk that engages at 3300. But, I don’t know if that’s good or bad because I don’t understand the various dynamics.

What should my RPM be for a 1/7th mile track and why? Max RPM is 6500 minimum while burping it in the turns is maybe 5000.

does my clutch engagement point matter? Why 3300 and why not 4000?
 

racing promotor

Moderator
Let me rephrase my question.

It’s a Bully 2-disk that engages at 3300. But, I don’t know if that’s good or bad because I don’t understand the various dynamics.

What should my RPM be for a 1/7th mile track and why? Max RPM is 6500 minimum while burping it in the turns is maybe 5000.

does my clutch engagement point matter? Why 3300 and why not 4000?
Yes it matters, for your application engage it at 3750 to 3800, WHY because that's what a lot of guy's do for clones and it works.
 

paulkish

old fart
The theory is engaged at engine peak torque
Practice is engaging it a bit under peak torque.

It nets out your engine makes the best power at peak torque.
Engage it too soon and you lug it.
Too late and you spin it needlessly where it isn't making its best power.

Without going back and reading Al's posts, he's probably explaining it ok to your corrected question.
 

paulkish

old fart
proly just listen to what was told about it in post #6 and you'll be ok and not have to worry bout the rest of the BS, including my BS.


not proly best it would be best
 

ggodwin

Member
proly just listen to what was told about it in post #6 and you'll be ok and not have to worry bout the rest of the BS, including my BS.


not proly best it would be best
I appreciate your BS. I just want to make sure it is aligned with what I was thinking.

So to increase the engagement RPM, I need to tighten or loosen the bolts?
 

XXX#40

2A supporter
I appreciate your BS. I just want to make sure it is aligned with what I was thinking.

So to increase the engagement RPM, I need to tighten or loosen the bolts?
Tighten but needs to be done equally, or if it has the weights on the arms remove them
 

alvin l nunley

Premium User
Before you do anything, find out where your engine reaches peak torque. I think you're pretty close to 3300 RPM.
 

JPMKarting

Premium User
I don’t have access to a Dyno. I’m just going to have to get as close as I can.
Adult clone is 3600-3800 engagement. Track size doesn’t matter.

a 1/4 turn down on the springs is 150 rpm.
 

rainman

Premium User
On 4 strokes I would engage it at higher than 3,300 rpms, especially if you are racing asphalt sprint tracks. I did make a mistake for more than a season and though I was running on top another guy was faster than me most times and tried everything else, but I found out it was the clutch engagement most times what was making him faster at most races. Again with 2 strokes I do like low engagement clutches that one engaged actually work like a Direct Drive, but on low power 4 strokes i would do as they are recommending you here.
 
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