# Resizing v belt

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#### RichardS

I use a ride on leave spreader at work that’s powered by a Subaru ea190v Thanks to a catastrophic failure that destroyed the ignition coil, I had to bolt on a new one. The old pulley that was on the shaft out of the motor was well rusted on, so I just replaced that as well, but with a slightly smaller pulley. I went from a 3.75” pulley to a 3.50” pulley, causing the belt to be a pinch too loose. I have no freaking idea how to size a new belt. So I just get one that .25” smaller? I feel like that’s the right answer, but don’t want to play a guessing game buying a bunch of belts to see what works. It’s fertilizer season, and I’d like it to be right the first time.

#### Oily_Thing

Sounds like a geometry problem. I suck at math, so maybe someone else will comment with the right answer.

#### PandaBear

Originally Posted By: Oily_Thing
Sounds like a geometry problem. I suck at math, so maybe someone else will comment with the right answer.
If you know the amount of contact on the circumference the belt land on, yes, but it is probably easier to just look up the application with that new pulley size and get the belt it goes with. Why did you downsize the pulley? Was it from another engine on the same block? If yes then you should look up the belt that engine use and buy it. I'd trust that approach more than just keep trying till you find a right size. delete my wrong calculation

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Half the circumference of the 3.75" pulley is 5.9". Half the circumference of the 3.5" pulley is 5.5" so I would get a 1/2" shorter belt.

#### Chris142

Use rope. Measure how long it needs to be in inches then find a belt that long and the correct width.

#### RichardS

I went with the smaller pulley, because it was the closest size available that fit on a 7/8” drive shaft that was available locally. Had I known quite what I was doing, I would have ordered a pulley when I ordered the replacement motor. This is the 3rd motor for this machine, so I don’t think the original info regarding the belt would apply. The OE motor was a Honda, the second (and now third) are both Subaru’s. I don’t know that the pulley on the previous Subaru came off the original Honda motor, or if it was added when the motor was swapped. The motor directly tethers to the gearbox to drive the rear wheels via this belt. The belt that is on there almost fits. It’s able to transfer some of the motors spin to the transmission on the spreader, but even with the belt tensioner, it’s just slightly too loose to spin at the same rate, and therefor doesn’t give me the necessary torque to move forward without the belt slipping and overheating the pulley on the drive shaft. Joshua, thank you! I had a feeling my math was too simple to be correct. Just as an FYI, because I feel like the question is bound to come up: it went through 2 motors in 9 years because my predecessor didn’t believe in changing oil on OPE, or any other basic maintenance, so they got ran into the ground on their first fill, and then replaced. Though I started following the 50 hour OCI in the handbook, 4 years on its first fill surely did its damage. Anyway, the second motor bought the farm when a magnet came loose and made contact with the flywheel, shredding things as it fired out from the protective cover.

#### andyd

Re-use the old pulley

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#### RichardS

Trav, Thank you! I’ll take a look at those, and hopefully it’ll pan out.

#### RichardS

AndyD, Trust me, I’d have loved to. But hours of hammering, pulling, and a night bathed in penetrating oil wouldn’t free up the pulley or key, so I surpassed my abilities with the tools available. If you’re a snowbird, and down this way for the winter, I’d be glad to DM you the address to give you a crack at it!

#### eljefino

Cut the old belt at a 45 degree angle then cut little bits off it until the new one fits. Duct tape it together and bring it to NAPA to compare to new ones. If you can read the number of the old one that will give you a starting point. Remember you want a belt to ride on the upper sides of the pulley and not bottoming out.

#### RichardS

Eljefino, Thankfully I have spare belts of the current size, as I doubt anything on the belt currently in service could still be readable. I’ll havw to give your method a go if the - 1/2” doesn’t do the trick. Since there’s a tensioner pulley, I’m not sure how snug it needs to be without that tensioner tightening it up I don’t understand the description of where the belt should ride. The groove the belt rides in is exactly sized to match the size/shape of the belt.

#### jhellwig

Originally Posted By: RichardS
AndyD, Trust me, I’d have loved to. But hours of hammering, pulling, and a night bathed in penetrating oil wouldn’t free up the pulley or key, so I surpassed my abilities with the tools available. If you’re a snowbird, and down this way for the winter, I’d be glad to DM you the address to give you a crack at it!
If the motor is junk cut the shaft off behind the pulley then drive it out easy as pie.

#### Linctex

What method is available to adjust the belt tension?!?!?!!?

#### RichardS

Jhellwig, I lack the tools necessary to quickly, or easily, cut through that much steel. I’d have to hacksaw it, and I don’t have that in me. Linctex, None that I could see. There’s a tensioner/guide that isn’t adjustable, and both pulleys are not able to be moved farther away from each other to take up the slack.

#### jhellwig

Another option would be to drill the shaft out as big as it can be drilled, take a cold chisel and collapse the shaft.

#### RichardS

Yeah, that sounds like a no, as well. I’m not set up at work to make major repairs, as my predecessor would just take the equipment to a lawnmower repair shop for this sort of stuff. My personal tool collection is also limited to what I need for basic maintenance for the Buick and caliber. Thankfully, getting a 30” belt, instead of the 31” that was on there, seems to have been a sufficient fix.

#### RichardS

I do appreciate the suggestion, though.

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