Motorized Bicycle Woodruff key

Re: Woodruff key

A sprocket that "wiggles" can cause all kinds of problems...which key do you mean?
Clutch?
Rotor?

Re: Woodruff key

You have a strange problem there...I got nothin.
Might help but I'd check for a bent shaft or bad keyway or something first. I don't see the rear sprocket causing this.

Re: Woodruff key

I'm with maniac on this one. Look for free play (rotational) between your sprocket and shaft, there should be -0-. A slightly wobbly rear sprocket won't break the woodruff key.

When does it break? Are you abusing the clutch?

Re: Woodruff key

The key way is coming out because when you put the gear back on it not going to stay in place .I suggest you to super glue the key way in the slot and let it set a day,or aleast an hour or so.then slide the gear on it.I know you won't have any problems after that.I've done it alot changing seals and gears.

Re: Woodruff key

Okay I also forget to tell you that there is two sizes of the wood ruff key the thinner one goes on the crank shaft and the wider one goes on the clutch and drive shaft.I don't know where your buying them at but you need the wider one for the drive shaft.Still glue it on the shaft.This is what I've done with bgf 's motors and grubees.I don't know for sure on other motor's

Re: Woodruff key

It may be cheaper and easier to change the rear wheel.

Re: Woodruff key

2door said:

Yep, cause you might have problems getting that Pirate adapter to work on a 48 spoke wheel. I believe they say on their site that their adapters are designed for 36 spokes.

Tom

Click to expand...

Manic Mechanics large sprocket adapter works with that 29" 48 spoke wheel
because 3 divides into 48

http://mmbikeparts.com/order.htm

Re: Woodruff key

Regardless if the wobble on the rear sprocket is causing the problem with your woodruff key, you need to fix that wobble. You will have nothing but trouble if you ride with that wobble. I had to put the rag joint on a 32 spoke wheel (its made for 36 spokes), three of the holes interfered with spokes. I had to make some new holes through the sprocket, rubber and brackets and put two bolts equally spaced between the three that interfered. After much tweaking I got mine dead center. So either spend some time and work out the wobble, get some kind of sprocket adapter that fits, or change your rear wheel. You need that sprocket to be wobble free....

On the woodruff key, this is not a a super common problem. Perhaps your motor sprocket isn't tightened down properly? If its a little loose it will jerk one way when you drop the clutch to start the motor, and then jerk the other way when the motor starts to pull the chain. Doing this time and again could cause that key to sheer. This is a hard nut to tighten properly, the spark plug tool they give you that tightens this nut is hard to use with good results, and the motor likes to rotate when you crank down on it. I recommend you go to the hardware store and buy a real socket that is the size of that spark plug tool (I forget how many mm it is off hand), use the real socket with a real wrench and you will get that nut tightened properly. To prevent the motor from turning over while tightening, remove the gear side cover, take a shop rag and double over the end a few times so its thick and put it between the big and small bevel gear so that it gets dragged into the gears when you tighten the nut. If you have a thick enough lump of rag there the gears will seize immediately and allow you to torque that nut, and the rag will come right out easily when done. (if your rag is too thin it can get dragged in and stuck in the gears, I like to use the doubled over sewn edge of a rag) Other people use other things, wood dowel, penny, one manual shows a screwdriver jamming those gears. The rag works well for me, I don't want metallic items jamming my gears. Also, I like to use some BLUE Loctite on that nut on the motor sprocket.

Re: Woodruff key

mannyphresh said:

...I bought a woodruff key grinded it down to fit then super glued it in place......

Click to expand...

I've heard the recommendation to super glue the woodruff key in the slot, to me that doesn't seem like a logical thing to do. The woodruff key is also referred to as a sheer key, which means it is designed to sheer (rip) if the tension is too great on the union. It is there to protect your motor in case something goes wrong (chain jam etc). Your key will still sheer and protect your motor, but with the bottom half super glued into the keyway I would worry that you will not be able to get it cleared out to put a new one in??? If you are unable to clear the keyway slot your kinda screwed. You would either have to grind it clear somehow, or replace the clutch shaft.... but the clutch shaft has the clutch plate attached, and the large spring mechanism, so replacing just the shaft takes some doing.... and an entire clutch assembly is kinda pricey..... kind of a PITA compared to just slipping a new key into a clean slot.

Instead of super glue I just use a tiny bit of blue loctite, let it set up a bit and you're good to go...

Re: Woodruff key

That's a good point nightcruiser I know blue loctite works too.I have done it too.I only put a small amount of super glue tho.I got the super glue from another user on here.I think is why because it Set's up quicker.Loctite takes a lot longer,just basically some thing to hold it in the slot when installing.

I had the same thing happen and fixed it by putting a crush washer (the ones for spark plugs) against the pinion, the flower nut fits inside, then used a impact drill to lock it in place. So far so good. My engine was three days old when my woodruff key came out. I was flying down the road and went to slow down when suddenly a chirp and vriiing of the engine as I lost output power

i recently switched over to the thinner 410h chain. had a machine shop cut a wider slot into a few thin sprockets that have the thin slot. also had him turn down wide gears to fit my chain. there is no quality control. the sprockets, woodruff key and hole cut in the crank are like snowflakes, no 2 are alike. some had the groove in the gear offset, wider, narrower. some of the gears are actually hardened some pretty soft. you might of had a mismatch between the woodruff key/gear/crank. maybe it wasn't torqued down enough. i use my 3/8th's drive air gun and was amazed how many turns it took to get the gear bottomed out against the inner bearing race on the countershaft.