Flywheels with cast in key - how to repair sheared key?

[TonyM]

All right, is there a standard accepted way to repair these kind of flywheels if a key gets sheared, or are you supposed to simply replace the entire flywheel? I don't like that set up. I'd prefer a seperate key. I suppose it saves on manufacturing costs not to have the extra part and not to have to install the tiny little thing, but is it worth it?

 

[NWCS]

one solution if you have the equipment, you could buy a keyway cutter or have a machine shop cut a keyway. the one problem with this is you have to know the exact location the keyway needs to be, and can be very tough to find on such a flywheel.

 

[TonyM]

I repaired one today by broaching out a keyway by sharpening the handle end of an old round file. I just centered it in the old keyway. The saw runs fine, but I was just wondering if there is some accepted method. I had to make up a custom shaped key to fit my concoction.

 

[NWCS]

this method might be crude and seem wrong.. but you could probly do it on one of those scroll saws with the right blade.. just set the table to the correct angle and cut a keyway with some patience. i have never done such a thing but you could put the blade through the hole in the flywheel.. fire it up and it should do a decent cut.

 

[Bob Wright]

When i was a Millwright in a big factory we made special fit keys. Sometimes you have to. Alot of times the key needs to be big to fit the flywheel and smaller to fit the shaft....Bob

 

[NevadaWalrus]

This is my proceedure, have done it many many times with about 98% success.

Get some fine grit, water based valve lapping compund. Do not use oil based.
First, score a line on the top of the crank and flywheel where the key alignment should be, important to be very accurate.

Next, paste the compund on the taper of the crank or inside the flywheel. Set flywheel on crank and lightly rotate round and round. Yep, you're lapping the flywheel to the crank to assure a good match. When you're satisfied its good, align the marks you previously scored, put on the nut and tighten to the proper torque. Leave the compound right where it is, the grit will further assist in holding it in place. This is why not to use a grease or oil based compound as it would make it slippery. The water base will dry and leave just the grit.

Can't take credit for this. Picked it from a web site about building B&S kart engines. This method is used by some of them for advancing the timing and eliminating the use of the alignment key. I know some of you hard core 2 cycle freaks may,,,,,,,freak out taking advise from 4 cycle racers but like I said, I've borrowed it many times. Got started using it because I hated telling Ryobi line trimmer owners that replacing a flywheel just wasn't practical cost wise. But since I found it works so well I now use it on any product that uses these cast in keys. Makes happy customers to save them a bunch of bucks.

 

[lucky]

Right on Walrus. The nut and taper is what holds the flywheel. The key is only for timing purposes.

 

[ehp]

I donot even use a key on most race saws because of the different coils on different flywheels, I clean the crank and flywheel and use the strongest locite you can get, let sit for 24 hours and off to the races.

 

[Al Smith]

Another bailing wire tip.A home made broach can be made from an old tap.Grind all flukes off but one.Grind the remaining fluke as square as possible and with about a 5 to 10 degree positive on the end.Use a heavy duty drill press or milling machine to do the broaching.Only nibble about 5 thou off at a time.
It would be a beech to hold the angle on the inside of a flywheel.The lapping method would work the best.

 

[lesorubcheek]

Hay NevadaWalrus

Man what a great idea! This is the kinda information that I joined this forum for in the first place. Not only did you pass on some killer info, but you gave credit where credit was due also. Way to go and thanks for the hint.

Dan

 

[davidwyby]

Old thread, good trick

@huskihl

 

[sean donato]

Outside of assembly the key has no purpose. The crank and flywheel are a taper fit. Have many many small engines that the key got tossed after a timing advance.

 

[HarleyT]

Nevada Walrus used to have his own site and forum, it was excellent!!