I need clutch help, new to karting

R

rocket7j

New member
We run a 2 disc bully, got a purple plate animal motor, and we run dirt oval. Driver is only been in kart for 5-6 tmes, but she's getting smoked on the starts. Once we are up to speed it's fine, but need some info on setting clutch, springs, maybe a newer clutch(ours is an old one). Can any one help? We know nothing about karting so remember we r novice. Thanks
 
The clutch should be slipping, on the starts, at peak torque.

One way to find that peak torque point in the rpm range is with a strong wall and a bathroom scale. Put the bathroom scale between the wall and the front of the kart. Warm the engine up, then floor it. It should only take a second or two to get your readings. Write down the scale reading along with the rpm on the tack. You adjust the clutch until you find the slip rate (called stall RPM) that makes the highest scale reading.
 
Adjust the nuts on the springs clockwise 1/4 to 1/2 turn at a time until you are no longer getting beat on the starts like you are now. Here is a chart to help you, you want it engaging at around 3200 according to Bully's website, which means you should have the spring height set at .215 from the bottom lip of the spring retainer to the top of the plate the spring sits into, can check this with a digital caliper or a Bully spring height guage. I would suggest investing in one of the spring height guages if you are new to these clutches and adjusting them. If you cant afford to do that, i would suggest what i mentioned first, adjust each spring 1/4 to 1/2 turn, then sit the kart on the ground on pavement or concrete in race ready shape, start it up and watch the tach on the kart, have your kid hold down the brake and start giving the kart throttle until the kart starts moving, watch the tach and you can see what rpm the engine is at when the kart starts moving, you want it to start moving at around 3200-3300 rpm. Dont hold the brake and keep giving it gas, just hold the brake and have her hit the gas for a few seconds then let off, holding the brake and gas at the same time for a while will burn the clutch up if you arent careful, just do it long enough to see what rpm the clutch is engaging and the kart starts moving, if that makes sense.

http://www.buller.net/Category/bully_2d6su
 
I would recommend sending the clutch to Tony power and have him take a look at it. Give Tony a call he will get you straight.
 
We always ran a single disk clutch with purple plate, more than enough hold and less weight to spin.

Are you sure it's the clutch and not gear ratio/combo?

Purple plates are unforgiving if she even a second later to the pedal than the other drivers.

I agree- have Tony Power hook you up with the right clutch/adjustment
 
What would be interesting is to find out how much heat the clutch is producing. Heat is a power loss, you want to make as little as possible while maintaining the rpm at peak torque.

Understand, if all the clutches are holding their respective engines at peak torque, the one producing the least amount of heat is the one getting the most power to the rear axle.

All clutches slip some on the top end, the one that slips the least, on the top end, is the most efficient one at getting power to the rear axle. With no evidence to back me up, I believe a two or three disc clutch is the better choice. The extra weight of the extra disc is insignificant compared to the weight of the kart and driver. Any calculation of the power required to accelerate something will include the speed at which you are trying to accelerated it. The faster you accelerate it, the more power it requires. From idle RPM to clutch engagement, the acceleration is very quick, even so, it's hard to tell the difference in that instance between a two disc and a three disc clutch. After lockup, the acceleration is relatively slow compared to that, that means the difference between a one disc and a two disc is even less significant.

Prove me wrong, measure the heat coming from a one disc and a two disc at stall RPM. I'm pretty sure the one disc is going to show more heat than the two disc.
 
I would check the idle RPM. It may need set up some. If you have 2 karts with the same clutch stall and one idle set at 2500 and the other one at 2700 and hit the throttle at the same time, the one set at 2700 will hit the clutch sooner and take off sooner.
 
Prove me wrong, measure the heat coming from a one disc and a two disc at stall RPM. I'm pretty sure the one disc is going to show more heat than the two disc.
Click to expand...

It is not my intent to prove you, or anyone wrong...but I can offer my experience. If the clutch is set up incorrectly or overpowered, then what you say would be absolutely correct. In the OP's case of a very limited power engien, I am not so convinced, and here is why.

Keep in mind that this is very difficult to quantify and repeat (at least with my limited abilities.)
Here is what I can provide for you to consider:

My claim: A one disc Bully clutch has sufficient surface area for a small plate (purple in this case.)
The temperature produced from slippage is nearly identical. On two back to back runs from 2000 rpm idle to WOT with the same amount of load on the dyno, each clutch (fresh single disc and fresh 2 disc Bully clutch (same oem clutch linings and surface finish/grind used)) produced the same amount of increased temperature (15* F) after a 20 second pull. With three add'l down pulls, the clutches each produced only slightly more heat (raising a total of 20* F) more than what they started at (ambient air temp at 78*.) Actually, the single disc clutch was a degree cooler than the 2 disc but I would assume that is within reasonable error for my Goodson temperature gun. Still both were cool to the touch after being run - that's what is important to me.

Clutches that build heat are slipping power away from the rear wheels. If they get hot, (I don't care how many discs they've got), they're robbing power. The more discs (same size diameter and surface width) a clutch has, the better it's ability to disperse heat across a greater surface area. For that reason, higher HP (more specifically torque since that's what we're concerned with clutching,) engines require more surface area in the clutch, ie more discs.
For purple plate animal, a single disc will be sufficient. If you find it getting hot, it may be out of spec or in need of being rebuilt.
On the other hand, a 2 disc really won't hurt your performance (seat of the pants anyway.) Interestingly, the weight of the clutch also has some input on where the peak total output of the engine (torque) lies. That's why you often times see builders recommending an engagement speed slightly different than the engine's peak torque on the dyno. For myself and my customers, I recommend to engage the clutch (single or 2 disc) AT peak torque.

FWIW: On our dyno, the clutch I typically use for engine testing has a belt drive and a very low engagement rpm so I don't miss peak torque numbers when making pulls due to clutch disengagement. When breaking clutches in though, we use a chain drive and normal engagement at peak torque.

For the OP, your problem is not the number of discs in the clutch, it is likely how it is set up or in need of being rebuilt.
It could be something entirely unrelated to the clutch as well (driver not anticipating the starts, engine power is down, dragging brake, incorrect gearing, driver, etc.) as well. If you'd like to give us a call here at the shop, I can offer my recommendations on your clutch settings. If it varies considerably, then we may have just found the problem. If my springs, spring heights, weights, air gaps, etc set-up is similar to yours, then it just might need rebuilt or start looking elsewhere for the problem.

-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
27 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Very good test and write up, thank you. I wonder if an on track test would duplicate your dyno results? Maybe an acceleration from a rolling start for about 25 yards with the clutch slipping at peak torque at the start.

To make things even more complicated, perhaps a solid mounted infrared gadget of some kind that could feed into the Mycron gauge on-board. Kind of elaborate I know, but I think the results would be interesting. The scientist in me wants to eliminate speculation. Eliminating speculation on which is better, one disc or two disks, could only help.
 
I would think an on-track test would only enter more variables, rolling resistance, track surface, wind, driver error, weight of car, tire pressures, grip, stagger, etc etc.
A controlled environment (as much as it can be anyhow) like a dyno test cell is better equipped for making back to back comparisons.
 
Thank you everyone for ur help. I've talked with bully about our clutch we have now and I described it to them, seams to be in pretty bad shape. They pointed me in the right direction for a new one and it will be set at 3300. We r gonna try the new one this week and see how things go and I'm gonna send out old one to have cleaned up, redone, and new parts put in and set for us. I will also be turning the rpm up a little this wek as I liked that idea as well. I thought about that but didn't know if it would hurt anything As far as our gears, we ve had help from several people that run this track with the same kart and motors and we r in the ballpark. She is getting faster so we have been adjusting the gears. Thanks again to all that helped.
 
CarlsonMotorsports said:
I would think an on-track test would only enter more variables, rolling resistance, track surface, wind, driver error, weight of car, tire pressures, grip, stagger, etc etc.
A controlled environment (as much as it can be anyhow) like a dyno test cell is better equipped for making back to back comparisons.
Click to expand...
I'm sure you're right, as far as testing the engine is concerned, but I'm talking about a clutch test. A 25-50 yard straight line test, with the clutch stall set at peak torque, Which is something else. My concern, in this instance, is not how much HP the engine is making, but how much heat is being generated in the clutch. I see it as two totally different things.
 
alvin l nunley said:
I'm sure you're right, as far as testing the engine is concerned, but I'm talking about a clutch test. A 25-50 yard straight line test, with the clutch stall set at peak torque, Which is something else. My concern, in this instance, is not how much HP the engine is making, but how much heat is being generated in the clutch. I see it as two totally different things.
Click to expand...

Al, I think you've just described we we call a "butt-dyno."
An acceleration dyno would do the same thing but without many of the variables of a moving kart.
To each their own.
 
Apparently I'm not making myself clear, I'm not dynoing anything with my straight line idea, I'm hoping to measure the heat generated by the different clutchs. I think it would be interesting to know which clutch generates the most heat, seeing as how heat is energy not going to the rear axle.

The difference in "heat generated" may be insignificant, I'm just thinking it's something we should know.

Many times I have heard comments that this or that clutch is better off the corners, my logic tells me, if there is a difference, with the slower one, it would show up as extra heat. My logic says; if two clutches are holding their respective engines at peak torque coming off the corner, and one is faster, there has to be a reason. I can't imagine any other reason other than a loss of energy to heat.
 
alvin l nunley said:
Apparently I'm not making myself clear, I'm not dynoing anything with my straight line idea, I'm hoping to measure the heat generated by the different clutchs. I think it would be interesting to know which clutch generates the most heat, seeing as how heat is energy not going to the rear axle.

The difference in "heat generated" may be insignificant, I'm just thinking it's something we should know.

Many times I have heard comments that this or that clutch is better off the corners, my logic tells me, if there is a difference, with the slower one, it would show up as extra heat. My logic says; if two clutches are holding their respective engines at peak torque coming off the corner, and one is faster, there has to be a reason. I can't imagine any other reason other than a loss of energy to heat.
Click to expand...

So...you're simply look at heat generated by the clutch.
That's exactly what I did on the dyno, recorded and shared the results on here.

The difference is that the dyno has controlled resistance (hydraulic, H2O, load cell, inertia flywheel, etc.) whereas a kart would have rolling resistance, tires, tire spring rate, smoothness of track, a small rock or pebble in the path of the kart, driver input into the steering wheel, wind resistance, etc. Just more variables added into checking 60' times than testing in the somewhat controlled environment of a dyno test cell.

From what I recorded, there was no difference in temperature produced using either a single or 2 disc clutch with the limited power given of a purple plate animal (OP.) Now, given a much higher output engine that could easily overpower the clutch, I think you'd see a real difference in temperature for the reasons discussed above concerning clutch disc surface area.
 
Carlson motor sports. We run adult clone 350 we been experimenting with small light clutches. We run a 1/10 mile dirt oval. Big pipe pro clone. We have noticed faster starts.We have tried a 2 ward revs. Liked them but after 2ND week was blue from heat. Would a revolution 3 disc be better. Was thinking of trying a single disc X5 I have. U think a single disc bully. Would be better. We Deglaze and service clutch weekly regardless of which we try.
 
fasttommy said:
Carlson motor sports. We run adult clone 350 we been experimenting with small light clutches. We run a 1/10 mile dirt oval. Big pipe pro clone. We have noticed faster starts.We have tried a 2 ward revs. Liked them but after 2ND week was blue from heat. Would a revolution 3 disc be better. Was thinking of trying a single disc X5 I have. U think a single disc bully. Would be better. We Deglaze and service clutch weekly regardless of which we try.
Click to expand...

You do not need a 3 disc for a 350# clone, 2 disc is exactly what you need, a single disc might work better than a 3 disc though. If the Ward clutch was blueing after a couple races, i would check the engagement and make sure you have it set up right, 3600-3900 engagement rpm. I really liked the X5 clutches, they work very well on the clones, just hard to get parts for and a pain in the *** to change the drivers quick without stripping the screws in the basket. With the Hortsman X5 and Reaper clutches, i just kept extra baskets with gears already on them to make gear changes alot quicker and easier at the track.
 
If you are dropping enough rpm in the corners to disengage your clutch, I don't care what small clutch you choose, you will roast it.
A 2 disc Ward should be fine if it is set up correctly. I would not use a single disc X5 -- I don't think there is enough surface area for the torque that your engine makes. It would work fine for a time or two, but if you ever disengage during the race (restarts) it will be inconsistent and the more it slips, the more heat it generates...on an on. Keep in mind that just about any time that you get a clutch hot, it will warp the pressure plate or backing plate and that will only lead to less contact area for engagement and even more slippage and more heat. I'm a firm believer that your clutch (no matter the brand) should never get hot to the touch.
I still have a few X5 parts here if anyone needs (drivers and baskets) new & used.


-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
27 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
What temps do clutches run during race conditions? I figure opens or stronger motors will slip more and have more heat just curious at what temps is there more to worry about.
 
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