View Full Version : Need advise on getting a sprocket off a motor..

06 October 2011, 1630
Hey I need advise on getting a sprocket off a motor.... It seems that the key holding the sprocket to the motor shaft broke at some point while I was riding it... and I believe that a piece of the key must be stuck between the sprocket and the shaft... I not sure when it happen or how long I rode it that way... Anyway, I tried using a gear puller, but that didn't work.... I was wondering if I heated it up with a torch if that would help and also if that would hurt the windings in the motor...
Thanks, Jimmy

06 October 2011, 1648
What type of motor and what type of sprocket? I assume it's a 7/8" shaft with a 3/16" keyway. Keys are not designed to fix a sprocket onto a shaft axially, only radially. For axial fixation we use the supplied set screws and occasionally shaft collars. It sounds like the sprocket was installed with an oversized machine key which makes removal difficult. For this reason I always use and recommend undersized keys (I'm talking a few thou here) which are available on Mcmaster. Another possibility I've seen is somebody putting a drop of 680 in a keyway. Before you torch it, can you post a picture or two? If it a matter of needed some "gentle" brute force, the correct tool to use is a large arbor press. This can be tricky depending on the size of your motor.

06 October 2011, 1652
stick the motor in the freezer, then heat up the sprocket with a heatgun. Then pry it off.

If that doesn't work, get a gear puller.

06 October 2011, 1705
hmmm. I was gonna say gear puller, but I see you've tried it. Torch.

06 October 2011, 1809
It's an Advance DC A00-4009 motor... I thought that I used the right size key as it slipped right in and then I set the 2 set screws.. Unfortunately it's still on the motorcycle as the shaft goes thru a hole that I cut into the bracket that the motor is mounted on, so putting it into the freezer isn't going to happen... I guess my main concern is, will heating it up with a torch damage the windings in the motor?

Ken Will
06 October 2011, 1834
I guess my main concern is, will heating it up with a torch damage the windings in the motor?

You want to heat the sprocket so it will expand. You want to keep the shaft cool so it doesn't expand.
Heat the sprocket a little then put some cool oil on the shaft, on both sides of the sprocket, repeat as needed.

06 October 2011, 1905
I'd still go with the gear puller while you're trying the heat. Tighten up the puller nice and tight, heat all around the sprocket hub evenly and then give the puller bolt a few sharp hits with a hammer. I can't think of any other way to do it.