The engine on my troybilt walkbehind mower is fried. I want to pull the stack pulley off so that I can measure the shaft and set out looking for a replacement.

the engine is a single cylinder, vertical shaft, 8.5hp Briggs.

Here are my questions:
1. does the hex nut holding the pulleys onto the shaft turn clockwise or counterclockwise? think I've had I've had smaller briggs engines (6hp) that were reverse thread but that was a long time ago, and my memory might not be right.

2. how do I block the engine from turning when I try to turn the nut? This motor has a manual start, so there's no flywheel teeth to pry against.

It should be the normal way,clockwise,so you'll turn it c/c to get it off. Air and a half inch drive gun would help immensely in getting the nut off,but in your case,carefully wedging a screwdriver between the fins on the flywheel should help get it off. Be very observant when you're doing this. Watch for stress on the fin. If it feels or looks like it's going to snap,stop and regroup. I've done it that way a few times in a pinch and haven't broken one yet. If you're going to look for an entire engine,including flywheel,then don't worry about it.

You can likely find the specs for the crankshaft on your engine from the model type and code numbers on it. The most common size is 1" diameter 3 5/32" long drilled and tapped 7/16 - 20, but yours could be different.

Without an impact wrench, I would do as golftech suggested for removing the retaining bolts.

To lock the engine without breaking something, rotate it until it is on the compression stroke, remove the sparkplug, turn the engine back to bottom of the stroke, load the cylinder with small rope(pull rope type)leaving a little hanging out, now when you try to turn the engine it will try to compress the rope and stop, when finished, back the engine off a little and remove the rope. Have a good one. Geo

First off, clean up the threads with a wire brush and soak them with a little oil, you probably have already done this.


As Golftech said an air impact is the way to go. However if you dont have one then using a wrench and tapping it with a hammer sorta does the same thing. You may not even need to block the engine if you are the wrench with a hammer. By no means stick a screw driver in the flywheel fins if you choose this method, you will never see the stress coming until one of the fins is laying on the floor. If you break a fin, then your engine vibrates terribly. Ask me how i know.
:)

I like geos method of feeding the rope into the cylinder head.

The rope in the cylinder works everytime. the only way to go if you do not have a piston stop tool...

Chuck