Drive-Sprocket / Clutch help!

[kgray9]

Hi all!

I'm new to this forum, so please be patient with me.

I got a small go kart with a 5HP 126CC Subaru Robin engine on it. I don't really know how to work on gas related things, being more into electronics. I finally got it to run after cleaning the carburetor 3 times. I looked up clutch to drive-gear numbers and it seems to be a 1:6 ratio (12:72). My setup is a little unusual though I think. From the 12 tooth clutch, there is a drive-chain that goes to another gear with 36 teeth and 12 teeth on it. From that 12 tooth is another drive-chain that goes to the drive-gear attached to the wheel (one-wheel drive). I think that gear is 36 teeth, but it is ground smooth! It has no teeth at all! I figured that out by just trying to drive it and hearing this loud grinding noise coming from the engine. What should I do? Do I just get a new 36 tooth gear to replace the broken one? Is the gear ratio even correct? Also, what would cause that to happen.

Thanks in advance!

 

[Denny]

Check all the sprockets for bent or broken teeth and replace as necessary. Also replace all the chains. Go to Gokart Supply web site and you can learn about it. You will also need 2 master links. Any more questions just ask away! We all had to learn sometime! Welcome.

 

[kgray9]

Hi Denny,

Thanks! I’m not sure what to get for a new sprocket. Also, would it be better to switch to a torque converter? I am going to use this go kart off-road, so I think a clutch is not good for my situation. If I got a torque converter, how would I hook it up instead of a clutch?
Thanks again.

 

[Denny]

We’re gonna need pictures of the rear of the kart at least. From all angles. And yes, clutches stink off road and tend to die an early death. Also going to need to know diameter of engine pto shaft. The easy answer would be to say put a 60 tooth sprocket on the axle and buy a TAV II cvt off of Amazon and a Genuine Comet belt. Add in some new #40 chain and a 10 tooth drive sprocket. BAM! Bobs your uncle and done. But the truth is it is not always as easy as that. That’s why we need more information.

 

[kgray9]

Here are some photos:



I was thinking exactly what you are thinking. I found a torque converter on Amazon (https://www.amazon.com/Torque-Conve...U,B082LRLF25,B07T1FL1TR,B08RHK2FBM,B07T1MNZ44).

P.T.O. shaft diameter is 3/4".

 

[Denny]

Oh boy. This is going to be a tough one. Can you weld? Because you are going to need to move some bars if you want to get the cvt to fit. May need to refit jack shaft for clearance for the cvt. If you want to go live axle you will need to weld on some brackets or plates to hold the bearings in place.

 

[kgray9]

Yeah, I realize that. I haven't welded before, but my dad has a welder and I solder regularly, so I think I can figure it out. It would be better to make it a live axle. I think this is going to be a long project over the winter.
So...
1. The engine and its mount needs to be moved over, which means I need to weld a new bar almost in the center that is identical to the ones the engine is on now.
2. I need a live axle with a new 32 tooth sprocket on it (it can't be a 60 tooth because then it would be too close to the ground).
3. A 3/4" torque converter from amazon.
4. New #40 chain.
5. I need to somehow weld on brackets/plates to hold the ball bearings for the live axle.
6. Move the jackshaft out of the way for the cvt.

Anything else?

Thanks!

 

[Denny]

Genuine Comet belt. The cheap belts have a greasy feel to them and burn up very fast. You will burn up a lot of them in the time it takes to wear out 1 Comet belt.
Other wise your list looks good.

 

[kgray9]

Ok. Thanks. Ill get to work as soon as I can and report back .

 

[Denny]

Good luck!

 

[madprofessor]

Good choice on the TC from Amazon. Note that it has 2 different sprockets, for #35 chain and the #40 chain that Denny mentioned. The #35 is 3/8", #40 is 1/2". Many more options for #35, and is usually the standard for 5hp. engines, but you can go heavier with the #40 if you can find the sprockets and chain you want. Note that you no longer need a separate jackshaft (and chain) with a TC, it's built into it. Here's some options you can learn from just by reading, and welcome to the forum..............
Go Kart Chain | Mini Bike Chain | Masterlinks | Chain Tools (gokartsupply.com)
Comet Drive Belts | Comet Torque Converter Belts | Go Kart Belts (gokartsupply.com)
UCP205-16 Pillow Block Bearing 1" Bore 2 Bolt Solid Base (4PCS) 688938512934 | eBay
1" Bearing Kit (3 hole) | 400400 | BMI Karts And Parts
AZ1411-40 - 1" Deluxe Flexpruf Solid Steel Axle Std End 40" | Go Kart & Mini Bike Parts | MFG Supply
Unihub - Sprocket Hub | AZ2556 | Azusa 2556 | BMI Karts And Parts
#35 Split Sprocket | 6335** | BMI Karts And Parts
Chain - Purchase by the Foot | 4006** | BMI Karts And Parts
Chain - 10' Roll | BMI Karts And Parts
Plastic Sprocket Guard - 9" | KM1081 | KM1081 | BMI Karts And Parts

 

[ONE-EYE]

I'd get a riser kit for the engine, get rid of the sprocket on the jackshaft, use the TC (30 series), change out to a 10T sprocket on a driver, and add a 60T sprocket on the axle. Should do fine with a #40,#41, or #420 chain. I like #420 personally but others work. Comet belt only. Good luck.

 

[Denny]

I'd get a riser kit for the engine, get rid of the sprocket on the jackshaft, use the TC (30 series), change out to a 10T sprocket on a driver, and add a 60T sprocket on the axle. Should do fine with a #40,#41, or #420 chain. I like #420 personally but others work. Comet belt only. Good luck.

He would still have one major problem. Not enough ground clearance for the axle sprocket. He has to keep a jack shaft.

 

[kgray9]

Yeah, I can only put a ~32T sprocket on the axle because of ground clearance problems. I could fix that with bigger tires I think, but I would rather keep the ones I have.

The TC has a jackshaft though. Do I still have to add another because of my setup?

 

[Denny]

Not if you just build on what you have.

 

[madprofessor]

1. The engine and its mount needs to be moved over, which means I need to weld a new bar almost in the center that is identical to the ones the engine is on now.

You can weld down a large plate all the way across the frame tubes that will allow you to move the motor, jackshaft, whatever anywhere you want. Just putting in more tubes means you're stuck with that position.
Slots cut into the plate would give you the sliding primary chain adjustment of the motor, in addition to the motor base's own slots. Mounting the plate itself to slide whole as a unit (slotted angle iron supports underneath for mounting the plate) would give you adjustment for the jackshaft, instead of having to use a separate chain tensioner. With a TC, the jackshaft is integral of course, no need for a jackshaft secondary chain adjustment for most applications, but you'll still need a separate jackshaft anyway because of the axle sprocket clearance issue.
You'll need to drive a separate jackshaft off the TC's output sprocket, then drive your too small axle sprocket from the jackshaft with a secondary chain. Pic of a chain tensioner on too long of a secondary chain attached below.
If you're wanting a 6:1 gear ratio, you can put a 12-tooth sprocket on the TC's output jackshaft, run your primary chain from there to a 24-tooth on a separate jackshaft, and run a secondary chain from a 10-tooth sprocket on that jackshaft to a 30-tooth axle sprocket.

 

[ONE-EYE]

He would still have one major problem. Not enough ground clearance for the axle sprocket. He has to keep a jack shaft.

Yeah you're right. I was assuming that he was getting rid of the wore knobby tires and using what looked like a 20x10-8 turf savers that it was propped up on.

 

[DukeKL]

Genuine Comet belt. The cheap belts have a greasy feel to them and burn up very fast. You will burn up a lot of them in the time it takes to wear out 1 Comet belt.
Other wise your list looks good.

Going to need a new belt as well and looking for something that lasts. Will try that Comet belt next. Need to finish installing the suspension on the truck this week before I can work on the kart and have some hobby time next weekend.