I modified a Trailmaster 150 XRX to put a bigger engine on it. Decided to go big and put a 420 cc(13hp) predator engine on it and have a 40 series torque converter on it. But I am running into a problem. It keeps burning up the belts. The torque converter was installed according to the instructions and is clean. I am wondering if maybe the 40 series is not beefy enough to handle that engine? Even though I have been seeing that they can go on engines as high as 18hp. As for the gearing, axle has the standard gear(39 tooth) that comes on that go cart. Tires are standard size too. And the torque converter has a 14 tooth gear that came with it. Is the gear ratio to high?Been using the Comet 203785A belt as that is the same belt size as the one that came with the converter. Tried the 203784A belt thinking maybe the other one was to big, but is it a bit tight. Any thoughts would be appreciated.
Burning up belts.
- Thread starter bessertc
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bob58o
SuckSqueezeBangBlow
39/14 =2.786….
There’s your problem.
what size diameter are “standard” tires?
If your tires are 18” diameter, you are geared to do about 86 mph at 4500 RPM
There’s your problem.
what size diameter are “standard” tires?
If your tires are 18” diameter, you are geared to do about 86 mph at 4500 RPM
bob58o
SuckSqueezeBangBlow
Try a 60T rear sprocket. And maybe a 12T front sprocket. Let us know what diameter the tires are.
Tire size is 22x10-10. So you are thinking the gearing in the issue?
Looking at the Speed Gear Ratio Calculator at gokartsupply.com. You are indeed right. With the gearing and tire size, it says the max speed is 84mph. In order to get it at a 40mph max speed which I feel is a more reasonable speed for a go cart, I will need a 60/10 gearing.
Edwin Spangler
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If youre curious why the stock sprocket didnt work, its because the gearbox that came with the kart had a built in gear reduction.
bob58o
SuckSqueezeBangBlow
With 22” tires, 6:1 gear ratio will work much better. I’m not sure what size your jackshaft is or what is the current pitch of chain you are using. If you can find sprockets that work (preferably with #420 chain or #40) to give you 6:1 ratio (like 10T and 60T) then you’ll be good. Correct that 3600 rpm will get you to 40 mph. This is much more reasonable. Torque and acceleration will be better. Belts will last longer.