Woodruff Key Comes Out

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allenl44

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Sep 29, 2009
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Have an 80cc (so called) engine on a Huffy Cranbrook. Have logged about 250-300 miles just riding through the subdivision and terrorizing the neighbors.

Appx 1 month ago, all at once, the engine was running fine, but the bike was not going. Inspection revealed that the woodruff key had come out and was lodged inside the gear case in some excess grease. Hum.. wonder how it got out of the keyway??? Put it back in place, and about 5 miles later - came out again. Even tried cleaning the crankshaft & keyway, and using locktite. In about 3-5 miles - came out again. Latest episode, lasted about about 2 blocks.

Additional, maybe useless info: With woodruff key in slot/keyway and small gear in place, teeth on small gear stick out appx 1/8" past (toward gear case cover) the large gear/clutch's teeth. Also, you can see behind the small gear and about 1/8" the woodruff key and slot/keyway is not covered by the small gear, however, the recessed area in the front of the small gear (where the big-headed screw goes) is flush with the end of the crankshaft. So, it appears that the small gear is seating properly on the crankshaft.

OK, enough (or too much) words. It's obvious the key is coming out to the rear of the small gear. Anyone experienced a woodruff key problem like this?
 

Norman

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Kind of sounds like the key way was cut in the wrong place or a little too far in on the shaft. I wonder if you could grind a little material off of the gear so it will go in to cover the key way better or a dab of J B weld on the shaft and key to help hold it in place one thing you might try is make a wood ruff key out of a little bigger one by grinding it see if you can make it fit the slot tighter.
Seems to me that the key should fit in the slot pretty tight I think I needed to tap it in place with a brass drift punch.
Could you post a photo if it? Then I'd have a better idea of what you have thats messing with
you.
You might be able to get it to stay in place with the loctite stud and bearing stuff. you might need to get the accelerate to make it work. or try super glue.
 

diceman2004

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Aug 26, 2009
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ok 1st i know nothing about the chinagirl engines , 99.9 percent of the gears i have seen that have keyways , have a setscrew on the key and another 90 degrees to the key . sounds to me you key isn,t very long ( might as well be using a ball bearing for all the good that would do )
why don,t you just get a new piece of key stock as long as the key in the shaft . then theres no way it can pop out .

i,ve never looked inside the cover of a chinagirl engine . is there a washer and screw in the end of the shaft , that would prevent the key from coming out the end of the shaft .

if theres nothing to stop the key from coming out the end of the shaft, a long key may " not " be a good idea , because it would be possible if the key came out that way it could bore a hole thru your cover
 

Kevlarr

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Jul 22, 2009
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Problem is it's a woodruff key so the slot in the shaft is half moon shaped. Yea there was a thread but I can't remember who it was or what they did to fix it.
 

diceman2004

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Aug 26, 2009
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ok now that i,m sure its ( woodruff keys ) , Allen , a picture is worth a thousand words .

i,m going to agree with Norm that the key is machined out of possition . the woodruff key should be totaly inside the key of the gear ideally .

as i have never seen one of these puppies apart its hard for me to think of a cure ...but

there must be a shoulder on the shaft for the gear to seat up against

can you make a washer to fit behind the gear , but over the stepped shoulder that will cover up the woodruff key , and prevent it from comming out

I ASSUME , what is happening ( figure A ) is the key has an oppertunity to come out .

is there room to make a washer fit over the open end of the key ( figure B )
 

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Kevlarr

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Jul 22, 2009
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Forgot that Reel Adventure had started another thread. Here's how he finally fixed his.

Thanks again guys. Well not one for waiting, I broke out the Dremel tool and some Guiness. I carefully shaved off some of the inner diameter of the small gear and it slid on about 1/8 " further. Made absoutley sure the key was positioned correctly before and after the gear was installed. Then I put on the spider crush washer thingy and screw and tightened it down tighter than fort knox. I took my big ace hammer and small screw driver and bent the teeth in on the spider washer thing so there was no play between the small gear and the screw.


Since not too much Guiness at this point I ran the mess out of it. So far so good!

Now I gotta figure out how to increase me idle!
 

allenl44

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Sep 29, 2009
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Thanks everyone. Had thought about making the i.d. of the smaller gear slightly larger where is would go about 1/8" farther back on the crankshaft. Seems it would make the two gears mesh better and place the smaller gear more nearly over the woodruff key (where it couldn't come out at the rear of the gear). But I didn't know what to do about the extra 1/8" or so of shaft that would now stick out into the recessed area in the front of the small gear. Saw where Reel Adventure bent the teeth on the "spider" washer thingy that goes on with the big-headed screw. Not sure that will take up the 1/8" or so that I will need. Anybody have advise about maybe just adding standard washers (slightly larger than the 1/2" +/- shaft) as spacers? Got some pics that Norm asked for, but this is my first forum and I don't know how to add/post them.
 

allenl44

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Sep 29, 2009
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diceman2004,
Not a bad idea. Thanks! The crankshaft does have a slight ridge about 1/8" from the shoulder which seems to be where the small gear is seating rather than the shoulder.
 

Norman

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can you measure the od dia of the shaft? figure out what size of spacer to cover the exposed
part of the wood ruff key make me a good drawing with measurements I could try to make you a spacer if I happen to have the right size material shouldn't be too much work. If I think of it I'll look at one of the engines I have and see just what it would take to make a spacer or shim. I'll do that tomorrow as it getting late.
 
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allenl44

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Sep 29, 2009
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alabama
All...
Thanks VERY MUCH for all your thoughts and ideas. As Paul would have said, here's the rest of the story.... I inspected the gear case area further and noticed that the small gear was thicker than the large one, and that the rear faces of the two gears were about even, i.e. the gears were meshing good. The overage of the small gear was just at the front. The o.d. of a standard 1/2" was t-o-o-o large. I used a 1/2" lock washer (spring type), bent the two sides of the split so that they were aligned, enlarged the i.d. to go on the shaft (appx o.d. 0.523"), and then enlarged very slightly more so that it would pass over the ridge (that was part way back on the shaft) and seat against the shoulder of the shaft. Once in place, I found that the washer/spacer was too thick. Put it in a vice and used a side/angle grinder to make it thinner. Once it was thin enough that, when installed, the small gear seated so that the recessed area in the small gear was even with the front of the shaft, I cut a notch in the washer/spacer's i.d. for the woodruff key. With the woodruff key in place, installed the new washer/spacer, then the small gear. Was a little tight, meaning that the gear didn't just slip onto the shaft/key readily. Had to mesh the two gears, then rotate the larger gear sightly back and forth (cw then ccw then cw) to get the slot in the small gear to go onto the key. Have put 5-7 miles on and, so far, all is GOOD. Before the mod, the key would come out in about 1-2 blocks. Thanks again to all who responded. You guys are the BEST!
 

Norman

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hey make sure that you aren't rubbing anything on the seal as it will not make for a good day.
if the seal gets damaged your engine will start running strange and possibly burn it up as it will cause it to run too lean with a leaking main seal.
 

MikeJ

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May 3, 2009
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Let me throw some more experience into this dialog. I replied to a problem thread posted by another reader. The screw holding the 20 tooth gear of his engine kept loosening and unthreading itself:

You asked, "So, has anyone ever had this happen? Why would it have come loose in the first place? Will it likely happen again?"

Answer: YES! Twice now to me! And I am prepared for it to happen again a long way from home.

IN MY CASE.... There seems to be a sequence of preceding events. When riding, I noticed a long stretch (maybe a couple of hours) of metallic "pinging" sound, as if the piston was smacking the cylinder head. Then I suddenly lost total power to the drive wheel, even though I could rev the engine (until I shut the engine down; then the engine would not turn over when attempting to start it).

I took off the right cover, just like you. In both cases, the screw you speak of completely loosened itself and the woodruff key fell out of the shaft. The application of blue Loctite from the previous event did not hold; maybe it softened with heat over time. Without that woodruff key, the 20 tooth sprocket cannot turn, though the crankshaft does.

With tools that I carry, I reassembled the sprocket along side the road. I was 55 miles from home at the time. The second time I reassembled, I put a dab of gear grease found in the gearbox on the threads. It is too early to tell if that will help. Upon reassembly, that "pinging" sound did not reoccur.

The woodruff key (the original) is beat up and severely deformed. I need to order a couple more, and maybe a new 20 tooth gear as a backup. I replaced the screw once just because the original one was beat up from the factory.

Expect this screw loosening to happen again. Loctite is not the final answer. Maybe check before each ride for a while. Periodic inspection and having tools available to fix along side the road is in your best interest. Hint: take a clean cloth with you. Spread it on the ground under the engine before you open the gearcase. If you lose that woodruff key in the grass and don't have a spare, you will be peddling. In my case, if I have to call ladyfriend for help, I owe her two expensive dinners. Two dinners will buy a lot of support parts!

MikeJ
760 miles to date. 65 miles after the second loose screw event.
 

Norman

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Use an impact driver on the scew it won't come loose. I know this for a fact. I think we wore this out.
THE END!!!!!
 
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