Shearing woodruff keys and stripping gears

I will pass on welding, what happens when the gear strips again?

Also I discovered that the gear wasn't all the way on the shaft from the factory. The gear mesh was OK but the key actually slipped out behind the gear.
 
DO NOT WELD the gear to the crankshaft!

If the woodruff key wasn't seated correctly that will certainly contribute to early failure. It will also allow the gear to not run true or move on the shaft which can also cause gear mesh to be off.

Take a good close look at the keyway in the shaft to make sure it is not worn or damaged. It must be a tight fit against the key and the gear keyway is just as important. They should be close to a precision fit. If not, you're going to have problems.

Tom
 
while i hope you luck with your endeavors I feel the need to point something out: like 2door said you may be having some other problem that this is a symptom of.
it would really suck to get your sprocket solid only to have your crank snap or something.
the idea of the key is to have a sacrificial part that breaks so more expensive/harder to replace parts can be saved. so it is a very bad idea to just "fix" the snapping key problem before diagnosing what is causing it.
chances are this is not an issue with your key or your sprocket, for example perhaps there's a warped set of links on your chain that is throwing the alignment off on something, or maybe a driveshaft problem.

basically what you should do at the least is make sure your crankshaft is balanced before you run it again.
this sort of problem could be a symptom of something much worse, your piston might not be mated to the crank properly, or you could have a crappy crankshaft that will do this over and over again until it gets replaced.
****, there could be a bad casting on your lower or something that's moving the gear/not Gripping a bearing correctly.

It sucks that the best advice for you is 'take the whole thing apart and go over it with a fine toothed comb' but it is what it is. again, good luck I hope you figure this out, and I hope it's a good story when you do.
 
GoreWound said:
while i hope you luck with your endeavors I feel the need to point something out: like 2door said you may be having some other problem that this is a symptom of.
it would really suck to get your sprocket solid only to have your crank snap or something.
the idea of the key is to have a sacrificial part that breaks so more expensive/harder to replace parts can be saved. so it is a very bad idea to just "fix" the snapping key problem before diagnosing what is causing it.
chances are this is not an issue with your key or your sprocket, for example perhaps there's a warped set of links on your chain that is throwing the alignment off on something, or maybe a driveshaft problem.

basically what you should do at the least is make sure your crankshaft is balanced before you run it again.
this sort of problem could be a symptom of something much worse, your piston might not be mated to the crank properly, or you could have a crappy crankshaft that will do this over and over again until it gets replaced.
****, there could be a bad casting on your lower or something that's moving the gear/not Gripping a bearing correctly.

It sucks that the best advice for you is 'take the whole thing apart and go over it with a fine toothed comb' but it is what it is. again, good luck I hope you figure this out, and I hope it's a good story when you do.
Click to expand...

As I posted earlier I discovered that the key fell out instead of breaking. This engine vibrates very little compared to others I've used and the timing is still stock, checked the magnet and it's key. I replaced the gear with a spare and it fit farther onto the shaft than the original, so that's the most likely problem.
 
rudyauction509 said:
As I posted earlier I discovered that the key fell out instead of breaking. This engine vibrates very little compared to others I've used and the timing is still stock, checked the magnet and it's key. I replaced the gear with a spare and it fit farther onto the shaft than the original, so that's the most likely problem.
Click to expand...

I was going to post about just that last night but couldn't get my kindle keyboard to cooperate... The tapers on the gear and on the end of the crank must also match very closely. If you get a gear that's got a different taper angle than the crank it's going on it can spin and eat keys as well (I'm assuming this is also possible since there are other China Doll parts that aren't interchangable etc).
Now that you got one that sits on the shaft better and lines up with the clutch gear better it shouldn't break any more keys. with the proper taper fit, you can even get away without even using a key and not have any slippage. On the centrifugal clutch setups, the shaft extension has no provision for a key at all and I've had mine up to over 40mph on several ocasions before the gear separated from the clutch bell on the centrifugal unit.

Anyway, I'd like to hear a report back how it's working now after you give it a few good test rides.
 
We're happy for you, Rudy :)

Let us know how things go from here.
Have fun and please, ride safe.

Tom
 
Excellent... Yeah, the teeth will get a bit of shine on them as they break in but that's all you should see... Just keep them lubed with a dab of grease every now and then and it'll last.
 
OK about 2,000 miles since the gear issues. Now the gear teeth are starting to wear thin again but for $4 to replace the gear per 2k miles it's not a problem. Also I started greasing the gear every ride vs once a week and the wear and gear noise have been reduced significantly. No keys have been sheared or dropped either.
 
I've got one setup on a 66 cc the pressure plate is painted with liquid steel and dusted with diamonds those where about 20 bucks try the last resort first the wet clutch might kept it from breaking try it..RE: Lucas #2 Wet Clutch
 
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