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If I were to put a smaller pulley on the rear of my old craftsman 5 speed maual to make it go faster, how fast could I get it to go. And how small of I pulley could I get away with without loosing so much torque that I wouldn't be able to get a a big hill? The engine is a 1985 B&S 11HP flathead.

crazyoldtractor said:

If I were to put a smaller pulley on the rear of my old craftsman 5 speed maual to make it go faster, how fast could I get it to go. And how small of I pulley could I get away with without loosing so much torque that I wouldn't be able to get a a big hill? The engine is a 1985 B&S 11HP flathead.

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Why do you want to go so fast are you going to race it.

No, not gonna race it. Its just fun to ride it around on my trails but doesn't go that fast. Its my beat up tractor I use for utility, towing stuff around, pulling, and fun.

It will be twice as fast if you half the circumference.... BUT it will have a bit less than half the torque.
You will also have a problem with belt slipping on a smaller pulley...

So you will have to determine how much torque you want to be left with... :smile:KennyV

KennyV said:

It will be twice as fast if you half the circumference.... BUT it will have a bit less than half the torque.
You will also have a problem with belt slipping on a smaller pulley...

So you will have to determine how much torque you want to be left with... :smile:KennyV

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Yep, I was just going to say, you'll loose torque, which on a mower, is low at the best of times.

I'd reduce the pulley circumference by 1/4 if I were you.

You will increase the speed a little bit, but still retain a reasonable amount of torque.

If you have room I would put larger pulley on the engine rather than smaller one on the transaxle because you will gain pulley surface and that means NO belt slip.
Then you can start shopping for a bigger engine to put on it. :biggrin:

Black Bart said:

If you have room I would put larger pulley on the engine rather than smaller one on the transaxle because you will gain pulley surface and that means NO belt slip.
Then you can start shopping for a bigger engine to put on it. :biggrin:

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Ah, of course, I didn't think of that!

Black Bart said:

If you have room I would put larger pulley on the engine rather than smaller one on the transaxle because you will gain pulley surface and that means NO belt slip.
Then you can start shopping for a bigger engine to put on it. :biggrin:

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will a regular drive belt stretch withought breaking if you do that?

This isnt a hydro is it? Hydros cant be modifed or theyll self destruct. Its not a matter of making it faster, youll need to do more then that- like brakes, steering, ect.

My first couple of mod tractors were failures, not in the speed aspect, but saftey - barreling around and no brakes = trip to the ER .

One the transmission broke on me - luckily as i was just taking off, if it happened while at speed, id be lucky not to be paralyzed.

The second was way too fast for a 90% stock tractor - after more then a couple near bad crashes, i took it apart- was too dangerous to drive it.

My current mods in progress will have good brakes, lowering, ect - built to handle faster speeds, not just thrown together like my previous machines.

Dangeroustoys56 said:

This isnt a hydro is it? Hydros cant be modifed or theyll self destruct. Its not a matter of making it faster, youll need to do more then that- like brakes, steering, ect.

My first couple of mod tractors were failures, not in the speed aspect, but saftey - barreling around and no brakes = trip to the ER .

One the transmission broke on me - luckily as i was just taking off, if it happened while at speed, id be lucky not to be paralyzed.

The second was way too fast for a 90% stock tractor - after more then a couple near bad crashes, i took it apart- was too dangerous to drive it.

My current mods in progress will have good brakes, lowering, ect - built to handle faster speeds, not just thrown together like my previous machines.

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whats wrong with hydro's and why?
mine is a hydro

Spinning a hydraulic pump faster than it is designed will drastically decrease its life (cavitation)... and can actually reduce its out put... Just because it spins faster will not make it move more oil...
Check with the Pump manufacturer for the recommended RPM, lots of things go wrong in a pump that's spun too fast... :smile:KennyV

Expensive noises to follow..
High performance "lawnmowers" are a great oxymoron, but they can be fun. PLEASE don't just make it go faster without doing the rest of what it takes to do it safely. Steering, brakes, chassis, drivetrain, engine mods, (especially if you are turning faster than stock RPM) etc.

I have a hydro murray , pulley on it is already like a 3 1/2 - 4" pulley - you couldnt go any smaller anyway.

Id suggest researching on building a modifed tractor , after my first tractor failure, i started looking at different setups , im not saying the second one was any better, i just didnt apply anything i learned tward it - that almost bot me more then one trip to the ER.

My future builds will be a whole lot safer, it might be fun to make a plain tractor fast ( i felt that way at first) , till a crash sends you to the ER- i wised up before that happened.

Now i think back, my first mod was scarey as my second, however the 3rd was a whole lot better by simple changes that actually cost me nothing to do and was still basically stock - lowering is a biggie- lower center of gravity makes for a more stable machine - can do this by smaller wheels, lower profile tires, lower the seat position ( might have to cut the rear fenders) - i bolted my seat right to the frame - front axle bolted tight- no swivel.

The difference was remarkable, it handles so much better sitting lower on the tractor, could throw it into a corner and not worry about flipping it over.