Clutch issues

[gtmud]

On my 30032 Yerf Dog, All new drivetrain, to the naked eye everything is lined up perfectly.
After it was driven all week-end, at first everything worked great, would even chirp the tires. I noticed that the kart was jerking allot at low rpm starts, especially to go up a hill, or even slight incline. If I mashed the throttle it would get up but jerk all the way up. I dismantled the driver and driven and cleaned them both. Applied a small amount of spray graphite to the driver inside face, and to the sleeve that the driven cam rides on. Also repositioned tension to position #3 on the Driven unit. Ran a bit better but still jerked on take off. I noticed that the new belt did fray a little on the cambered side. Any ideas.. Both driver and driven are new units from gokart supply. Belt too is new and correct for the crank to jack shaft spacing @7 3/16".

 

[OzFab]

Are you sure you have the correct belt, remembering that, apart from length, there are two different types; symetrical & assymetrical. Just a thought...

 

[gtmud]

Good question, but yes I have the assymetrical belt for the 30 series driver and driven units. I had no problem when I started to run the cart, but by the next day I noticed the jerking issue. Thats when I took it apart and cleaned everything, the "fraying" I noticed seemed to have stopped, I figure it might have to do with the break-in for teh belt. I still have the old driver, going to clean it and swap it out and see what happens. The original driven unit was a 7", I mistakenly ordered the 6", could that have something to do with it? Again the belt I ordered was for the 6" driven with a space of 7 3/16 between crank and jackshaft. Frustrating after all teh time I put into this cart!!! Thanks for teh reply Fabroman.

 

[ArachnidBrosMN]

I have also experienced a "chirp" when my 40 series engages on a kart that I personally think is geared too HIGH. My new belt actually was doing well even with the "chirp" to get it fully engaged. When I was done riding, I felt the belt, and it was pretty dang hot... I'm afraid that I will be burning through belts if I don't gear my kart lower. If your original kart had a 7" driven, then it would have engaged at a lower ratio than a 6" driven would engage at. Maybe that 1" of outer diameter has geared your kart a lot higher. Have you calculated your overall ratio?

 

[gtmud]

No, how do you do that. Thought the 1" differance might be part of the problem. Just want to be sure before I spend any more $$.

 

[gtmud]

Took the old Driver and cleaned it up, did not apply and spray graphite and installed onto the Yerf Dog. Ran it all weekend, everything seemed to work really well. Not sure if the NEW driver is faulty orjust not broke in yet. I think for now I will keep the old driver on the cart and maybe switch out the springs. Anyone have problems with items from Go Kart Suppy. I used them mainly due to the mass amount of info that they have posted on their site. Very imformative!!

 

[ArachnidBrosMN]

Hey, sorry for the late reply... if you go here:http://www.diygokarts.com/speed-calculator.html You will see how to calculate your overall speed (maybe your kart is geared too high/fast)

BUT: to calculate your overall gear ratio, you need to count the number of teeth on the back of your torque converter, and count the number of teeth on your axle-sprocket. (for instance, if your torque converter has a 10 tooth sprocket on it, and your axle has a 60 tooth sprocket, then your smaller sprocket (10t) will have to spin 6 times, before the larger (60t) sprocket spins ONCE. A torque converter system ADDS more gearing to your kart. Think of when your torque converter first engages. A "little" pulley is driving a "bigger" pulley, giving you a lower gear reduction.

If you scroll down on this page:http://www.bmikarts.com/PDF/Comet_40series.pdf
You will see that a 7.5" diameter driven unit (a "40D") initially engages at a gear ratio of 2.43:1 ratio... which you would ADD to your (example) 6:1 gear ratio from the torque converter to the axle (mentioned above)... for an overall reduction of 8.43:1. Accordingly, the 8.5" diameter driven unit initially engages at 2.83:1, which would give you an overall ratio of 8.83:1. BOTH clutch sizes (7.5" and 8.5") ultimately end up at a 1:1 ratio (clutch transferring the exact speed of the engine to the sprocket off the torque converter) BUT they START at different engagement-ratios, one "lower geared" than the other. The kart I just finished this month has large 25" diameter tires, and even with a 2.43 initial engagement, and a 7:1 sprocket reduction (10 tooth to a 70 tooth)... it was geared TOO HIGH (fast). So, I tried an 80 tooth sprocket on the axle instead of a 70 tooth (8:1 sprocket gearing ratio)... and it helped.. but it sill is fast!

I guess what all this says is, the LARGER driven unit (your old one) gives the go kart .40 LOWER reduction than the SMALLER driven unit. Which MAY be your belt-chirp problem. You may have to get either a smaller sprocket for the T.C. or a larger sprocket for the axle (to gain a lower-gearing to prevent the belt from burning)
Good luck with your project!