Motor pulley super hot

Hi, just upgraded to a 12t 5m 15mm motor pulley and belt to match and also added an idler…

Even with the belt seriously loose the motor pulley is getting very hot at high speeds…

Is the motor pulley too small?

Any advice?!

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why so sure the heat came for the pulley, not the bearings?

Because the motor is cold…

He’s talking about the idler bearing

Motor pulley is to small, your putting a lot of strain on the belt to force it around that small radius of the pulley leading to heat. Belt lifetime is going to bed bad with that setup.

Idler is cold…

What minimum would you recommend for the motor pulley with 5m 15mm belts? I really like the low gearing for starts and hills so want to keep it as small as possible… it was supposed to be a 15 tooth but the seller delivered the wrong size…


Check and see if is rubbing on the inside flange of the motor pulley

get a sharpie like a silver one and mark it all up and then a run it at speed on the bench and check to see if the mark has rubbed off

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i found 14T to be the minimum for me, im running 14/40, I tired 12 its too small even with idler.

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Same thing for me, 12T is too small and bends the belt too much, the lifespan goes way down

Yeah 12T is just crap, go for 15T. I’ve also used 12T before but the belt slipped a lot and I also got a hot belt.

Thanks for the input!

14t ordered…

Hope it doesn’t change the torque too much, this thing pulls like a train!

Hey man, I’m hunting for a pulley myself, I need to downsize from the 15t for more torque. Mind sharing your source? I’m having trouble finding anything

I found mine on eBay, just searched for HTD timing pulley 5m 15mm