Engine Drive Sprocket Case

GoldenMotor.com

Mjkx8

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Jun 22, 2011
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Hey. So I have a grubee skyhawk kit. I was riding my bike and I had to make a turn, so I turned and there was a car, I didn't have enough time to pull back on the clutch and I just squeezed the brake. The bike bogged and as i got around the car it kept bogging (starting and stopping rapidly) then I squeeze the clutch lever and it doesn't freewheel, ie. it didn't do anything. Finally the engine stalled, as I tried to start it back up again I pulled the clutch lever and the damn thing wouldn't free wheel, the clutch was doing nothing. I took off the Drive sprocket case and looked at where the camshaft is, and there was a chunk scraped off of it and below that there was a small hole in the metal, above opening for the camshaft. Should I get a new sprocket case and camshaft or is there another problem going on here? It is noted that the bike had no major problems like this before this incident. Thanks. Any help is greatly appreciated.
 

Mjkx8

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Jun 22, 2011
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Here are some pics:



Notice the big scrape above the hole for the camshaft, and the scrape/hole below the hole for the camshaft. Thanks guys! :)
 

MotorBicycleRacing

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Jul 28, 2010
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Don't those SkyHawks use bicycle chain?
Looks like the chain did the damage.

Did the chain bunch up and jam when you had the problem?
You can see where the chain usually hits on the cover on the right
and grinds its own clearance.

Do know how to remove the cam shaft by turning it so the pin clears?
You took the same pic instead of turning the arm to where we could
see the cam surface or just remove it.

Buying a new cover seems to be the plan.
 

2door

Moderator
Staff member
Sep 15, 2008
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The damage to the top area is where the pin that holds the cam in is at. Most of the pins are pressed in then secured with a dab of epoxy. Looks like the pin could fall out. I'd suggest mixing up a little epoxy and putting over the end of the pin to keep it in place then taking a good look at your chain alignment and tension.

Your chain might be too loose and/or the alignment is way off and the chain is being dragged outboard against the aluminum cover.
Another theory is that the whole clutch shaft has shifted to the left which would allow the chain to hit where it did.
Either way I wouldn't worry about the damage as pictured. But you do need to find out why the chain hit and fix that. The cover can be used as is after the repair as stated above is done.
Tom
 

Mjkx8

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Jun 22, 2011
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okay thanks guys, i don't know how to take the camshaft out...i am a noob. But I should just fill that top hole with some epoxy? The chain did not jam, it was on the drive sprocket as it should be and the chain is fine, i suppose it is possible that it is not aligned correctly. The big thing that happened was that when I squeezed the clutch lever it did nothing, it pulled the clutch arm back but had no effect.
 

2door

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Staff member
Sep 15, 2008
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To remove the cam from the cover the cover must be off the engine and then rotate the cam while pulling outward on the arm. The pin I mentioned aligns with a flat spot on the cam allowing it to be pulled out of the cover.

Now to your clutch problem: Make sure you have the parts installed correctly. In the center hole of the engine drive sprocket there are two parts. The first that goes in that hole is a ball bearing, about 5/16" in diameter followed by a steel pin the same size and about an inch in length. Install the cover (clutch actuator) and adjust the cable so there is little to no slack between the cable guide and the clutch actuator arm.

My guess is that while you had things apart you lost one or both parts, ball and/or pin, and that's why your clutch will not disengage.
Let us know what you find or if these suggestions don't work for you.
Tom
 

Mjkx8

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Jun 22, 2011
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Okay, so I bought a new cover but there is no pin in that tiny hole. On the old cover the scrape is right over that pin, so if that pin is supposed to move in some way I doubt it would.
 

2door

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Staff member
Sep 15, 2008
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Littleton, Colorado
The pin is not supposed to move, It should be peened or epoxied in place so it can't move. That's the idea of the design. If your new cover does not have that pin you'll be right back where you were with the old one. Take the advice I gave above. A 3/32" pin should be secured in that hole so it can't come out.
Tom
 

Mjkx8

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Jun 22, 2011
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On the "old" cover the pin is clearly still in the hole, it is just that the chain must have scraped against where the pin is, would that be a problem? I mean the pin is definitely in there, and now that it got scraped it is probably held in that tiny hole with more security. I'm still not sure if that is the problem, I haven't tried to put the thing back together and try it again. Tomorrow I will.
 

Mjkx8

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Jun 22, 2011
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Well I also noticed that I'm missing the bucking bar, which could have been the problem all along. So I ordered another one, and we'll see when it arrives.
 

crassius

Well-Known Member
Sep 30, 2012
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this is a 3 year old thread, but I usually just drill thru & stick a small machine screw in it