10 Tooth Drive sprocket wobble

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Farthom

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May 16, 2010
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I suspect this started happening as a result of my chain coming off and getting jammed in the drive sprocket last week. I am noticing my chain, does not have a consistent tension. It goes from loose to tight, to loose, as the wheel rotates. I have checked my rear sprocket, and its fine. I have found the tension changes directly correspond to the drive sprocket position. Every 1/2 turn, it goes loose, then 1/2 turn again, its tight. Upon visual inspection, it does have a bit of visible wobble. I took the sprocket off, and cant see any problems with the naked eye. After putting it back on the problem is still present. I really have no idea what to do from here. Do I order a new sprocket, and hope that was the problem? Hopefully nothing internal is bent. I don't think I posses the needed skills/tools/knowledge to dismantle the whole engine to replace something inside.

Please advise! Thanks in advance.

Farthom
 
Cabinfever1977

Cabinfever1977

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Mar 23, 2009
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Its your rear sprocket. It may not look off, but it only takes a milimeter for the chain to go loose/tight/loose/tight/loose/tight, happens to many people.
Took me 4-5 times to get my sprocket centered, just happened to get lucky finally and now my chain keeps mostly the same slack.
 
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Farthom

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Alright, I will definitely put some more work into that rear sprocket tomorrow. It's just strange, how the tension doesn't correspond to wheel position. What I did, is rotated the rear wheel, until the chain went tight, and marked the rear sprocket. Then rotated it further, until it went loose, and marked a different mark. Through EXACTLY ONE full wheel rotation, it goes loose/tight about 4 times. Also the tension after that one turn, is not the same as when I started, (wheel in the same position.) This is what initially led me to suspect the drive sprocket. Following this, I started again, putting the wheel in a position, where the chain was tight. Then I removed the side engine cover, and used the sparkplug tool to turn the drive sprocket 1/2 turn, and the chain was loose. One more 1/2 turn, and it was tight again.

So yeah, I'll mess with my rear sprocket again tomorrow, just in case. Nothing would make me happier, than to discover I've been talking out my rear, and it was the rear sprocket all along, however all signs seem to point at the drive sprocket. I suspect the chain jam bent something. :s


Let me know what you guys think. If I make any progress on the rear sprocket I'll let you know!

Thanks again,

Farthom
 
corgi1

corgi1

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Aug 13, 2009
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I under stand what your saying and it is possibly serious,,,the clutch shaft the motor sproket is bolted on the end of is probibly bent,,,I am guessing you were going along pretty fast when the chain did it's jam-up,,,I would think replacing the shaft the only option
 
2door

2door

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Sep 15, 2008
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I concur with Corgi1. I fear you have a bent clutch shaft. Try this: Remove the spark plug so you can rotate the engine easily by hand. You don't have to spin it fast, just enough that you can take a good look at the drive sprocket as it rotates. If the shaft is bent you should be able to see it easily. Watch the center of the sprocket and the teeth.
I would also suggest you take a good close look at your chain. A severe jam could have twisted it and/or caused a few rollers to bind. That will also cause the problem you're having with loosening/tightening. Get back to us with what you find.
Tom
 
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Farthom

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May 16, 2010
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Alright here's an update. I only had 2 hours of daylight to work in, as I was at work most of the day, and don't have a garage. With the bike upside down, and spark plug out, I was able to shift the bike into a higher gear, and watch the drive sprocket. It does have a pretty serious wobble.

I took the drive sprocket fully off, and with it laying on a flat surface, I took the attached picture. Sorry about the cheap Rubik's cube in the picture, my retarded camera wouldn't focus on the sprocket without it. The whole thing looks like its limping to one side. I'm like 90% sure now that I just need a new drive sprocket. Let me know what you guys think. I need to make sure I figure it out 100% before ordering parts. Its expensive as heck to ship things to Canada. Will likely cost me 40 bucks just to get one drive sprocket.


I guess I'll take the engine apart from the other side, and try to get the shaft out. Then I can roll it across some flat surface to see if its messed up. It was too tough to see any movement on the center axle while spinning the bike. Even with the spark plug out, the whole bike shakes a bit too much to get a good look. Hopefully its only the drive sprocket.

I wonder if I might be able to grab a hammer and beat the thing back into place. (The drive sprocket that is.) Would save me 40 bucks.


Farthom
 

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corgi1

corgi1

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Aug 13, 2009
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Leave the pin and ball bearing in the center hole and spin the engine again and see if the pin woobles w the shaft
 
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Farthom

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May 16, 2010
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Alright, here's the results of a little experiment I did. I stuck my sprocket on the end of a dremel, using some electrical tape as a shim, over one of the grinder bits. After powering it up, the sprocket appears to spin PERFECTLY with no wobble whatsoever. Spinning the bike with the clutch pin in, made it pretty hard to identify wobble, just because it doesn't sit perfectly in line with the shaft. In light of the above, I am now pretty sure that its the shaft, despite being previously certain it was the sprocket. When I place my order, I am going to play it safe, and order both. Shouldn't cost me much extra, since they will get shipped together.

In any case, before I put in the order, I would like to take the clutch apart, and get the shaft out for inspection. I am completely clueless on how to do this. I took the cover off the clutch, (the one covering two gears) and am now dumbfounded on how to continue. Can anyone provide some instructions, or possibly a link to a guide?


Thanks a lot guys.

Farthom
 
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Farthom

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May 16, 2010
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Alright. Seems I am going at it the wrong way. Not a fan of doing a complete engine disassembly just to get this thing out. :/

Armed with these helpful animations, I should be able to get it done. Hopefully I don't break anything doing this procedure.

Am I going to have to take the clutch apart too, to get the shaft out? From the pictures, it definitely appears so. Seems I'll have, a regular ol bike for a little while. No biggie, I can try to work off this growing gut.

Thanks!

Farthom
 
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Farthom

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May 16, 2010
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Should I leave the engine on the bike while working on it? Or should I remove it, and work on it individually? I don't really know what I'm getting myself into... which would be easier?
 
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Farthom

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May 16, 2010
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Alright, so I think that was a dumb question... didn't quite realize just how much I will be taking this engine apart. Once I get the engine off the bike, can you guys suggest a strategy, for how to take it apart? Like, what bolts to take off, and in what order, so I don't dismantle it more than I need to. If I understand what I will be doing completely, the whole engine is basically going to split in two. Any tips on what to be careful of when taking it apart, or putting it back together? Will I need to replace any gaskets? etc. This will be a first time for me. Any pointers are appreciated.

Also, if its important, I have the Grubee Skyhawk engine, not the Flying Horse model. The engines seem similar, but I don't know how different they really are, or what complications I may encounter.

Thanks guys for all your help

Farthom
 
BarelyAWake

BarelyAWake

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We don't disallow crosslinking to other sites, even "competitive" ones... but... we do kinda prefer if you quote or post the content here for rather obvious reasons lol

We don't really see it as "competition" so much as adding to our already extensive database, building the most comprehensive site possible - the name of the game being the free exchange of information really, not so much the "us vs them" thing.

In fact part of the reason this forum was founded was to avoid such drama ;)

Still, thank you for your consideration :)
 
corgi1

corgi1

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We want to know too ,thats why we're here,like a Borg collective verses stumbling in the dark giving and recieving imfo.
 
corgi1

corgi1

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Aug 13, 2009
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If your the same guy ,I think I sent a contact to this thread or yours to one of you when I saw your tear down thread,too get you two together
 
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