G16 with power spring shearing off woodruff key

[bryfree]

Hi,

I needed some extra torque to climb some steep hills, so a few months ago I installed a power spring kit. However, now the woodruff key in the secondary clutch keeps getting sheared off. I have a new input shaft, new clutch sheaves, new drive belt and new woodruff key, and it will only run for a few hours until the woodruff key is toast.

Any ideas what could be causing this?

Thanks,
Bryan

[bigstik40]

Just a couple possibilities to check:
1. The shaft taper and the outer clutch sheave taper may not match. This will allow the outer sheave to loosen and put excessive pressure on the key causing it to fail.
2. Not tightening the secondary clutch nut to the proper torque could cause the same thing.

Check the shaft and sheave tapers for burrs when you have it apart. You could also rub permanent magic marker on both tapers, then assemble the sheave without the key and rotate (grind) the sheave against the shaft. Remove and inspect the sheave and shaft tapers to see how much magic marker was removed. This may help determine if the tapers are a bad fit.

Good luck - RAY

[bigstik40]

Just thought of a couple more items that could cause your problem.
1. If the key slot in the outer sheave is not machined deeply enough, the key would bottom in the slot before the two tapers engage. This could cause problems.
2. If the woodruff key slot in the shaft is not machined deep enough, the key would sit too high and bottom in the slot of the outer sheave before the two tapers engage causing a similar problem to #1.

More things to think about, hope this helps - RAY

[bryfree]

Thanks for the ideas, Ray. I'm gonna dig into it a little further and see if I can figure it out.

[sho305]

You should put a new nut on with a spring kit, the locking part goes away and they come loose on you. You can put valve grinding compound on them and rotate to seat the taper better just like grinding a valve. The lawn racing and gokart guys fit flywheels that way all the time. Then clean it off and you should have a good taper fit. The taper is what takes the power not the key, they run flywheels with no keys and have no problems unless they backfire. Taper needs to be clean when you put it together. I put wd40/etc on them then wipe it off, but would not if I had an issue with it holding then I would put it on dry like they recommend. Usually with a cart you don't have the power to bother them. I would guess the nut is coming off by itself and/or it has a poor fit causing movement that makes it come off. A taper makes the two act as one part, they don't move at all.