Crank & Clutch Gear out of Alignment

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RPM

RPM

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Jun 7, 2009
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It seems I may have another problem with my new 68.5cc engine. With just over fifty miles I noticed a “clanking” noise coming from the primary clutch cover. I don’t get this noise on my 49cc so I popped the cover off and noticed right away that the crank gear is way off center on the clutch primary gear. (a hair over 3mm) This can’t be right so I popped the cover off on the 49cc just to make sure and my suspicion was confirmed. Its not that way on the 49cc. The two gears mesh properly and are in almost perfect alignment with one another.

If anybody has run into this problem before or knows how to get this gear in closer to align with the clutch gear I’m all ears.

I’m not gonna start tearing this thing apart until I find out more about it and I don’t believe it’s a good idea to ride the bike this way cause already I see some slight abnormal wear on the gears.

The first pic is of the 49cc primary and drive gear. The alignment is perfect. The second pic is of the 49cc but a different angle. This is the way it should be on the 68.5cc but its not.

The third and fourth pic are of the 68.5cc primary and drive gear. As you can see its way out of alignment.

RPM
 

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Creative Engineering

Creative Engineering

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Sep 20, 2008
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Clearwater, FL
web.tampabay.rr.com
RPM,

Norm is right...I would definitely pull the crank gear and have a look.

I've had a bunch of these engines apart, and every one has had the key slot cut so close to the bearing that it's a real pain to seat them properly. The key tends to roll in the slot.

Pull the gear off and remove the key...slide the gear back on and check to see if it goes on far enough to be flush with the clutch gear. If it does, then you know it was the key that was holding it off. Check the fit of the key in the slot. When inserted into the crank the top face should be parallel to the crank centerline. If it isn't, file the end nearest the bearing until it will lay in the slot correctly.

The end of the crankshaft is slightly tapered, (2-3 degrees), so is the bore of the gear. If you slide the gear back on without the key and the gear rests in the same location as shown in the photo, standing off from the clutch gear...there is nothing you can do about it. As long as the crank gear does not hit the cover, it really doesn't matter. The crank gear has been wider on every engine I have torn down. Usually the excess width is biased to the rear. It appears that you have full engagement, so as long as nothing else is wrong, and the gear isn't hitting the cover I wouldn't worry about it. The accuracy of the taper will determine the location of the gear during assembly.

Jim
 
RPM

RPM

New Member
Jun 7, 2009
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Michigan
Hi Guys,

Hmmm, the accuracy of the taper will determine the location of the gear during assembly.
I'm hoping its not a manufacturing error on the shaft.

No I didn’t receive a gear puller. Unless this is what your talking about in the picture. Its my understanding this is a clutch puller. I guess, I don’t know unless the inside of the gear is threaded.

What is that button or cap with the slot in it in the center of the gear? Does this unscrew with a regular screw driver or do you have to take a punch to break it first? Once this cap or button is removed do I need a gear puller then to take it off or does this tool screw into the gear then the center bolt forces it off the shaft as it's screwed in?

RPM
 

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Creative Engineering

Creative Engineering

New Member
Sep 20, 2008
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Clearwater, FL
web.tampabay.rr.com
RPM,

That's the tool. The way it is set-up now is correct for pulling the crank gear.

Yes that is a machine screw with a large slot for a screwdriver. You may need to use a punch to get it loose. push a rag into the gears, (at the top), in order to keep the crank from turning while removing the screw. When you put it back together, use locktite Blue. If you do not have an impact driver, the kind with screwdriver bits that you hit with hammer, use a punch to get the screw tight.

Yes, the gear is threaded internally...make certain you have installed the puller all the way, or you will strip the threads. put the rag at the bottom of the gears and use a wrench on the puller, not the puller bolt, to ensure that the puller is fully seated.

This puller is also used to pull the clutch hub and large gear assembly. It is also used to remove the drive chain sprocket on the other side.

Jim
 
RPM

RPM

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Jun 7, 2009
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Michigan
Ok Jim, sounds like a plan. I'll see if I can get at this tomorrow. I'll keep you posted on what I found.

Thank you

RPM
 
RPM

RPM

New Member
Jun 7, 2009
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Michigan
Well I was able to get the drive gear off today and check it out. I took the keyway out and slid the gear back on and there didn’t seem to be anything obstructing it. Looks like it was a manufacturing flaw.

I put it all back together and smacked the gear a few times to make sure it was seated and loctited the retaining bolt.

As you can see from pic two the drive gear is riding about three quarters of its width on the clutch gear. It doesn’t have full engagement. Neither does the clutch gear but is engaged more than the drive gear.

On both my bikes I do keep these gears lubed but I may contact the seller about this. One thing I noticed about this engine there is a lot of end play (sideways movement) with the crankshaft. I’m just guessing but I would say at least .020. I don’t know if that's normal but it may be the reason why this engine is so loud and vibrates the way it does. Sometimes I think its going to blow up because its clanking so much. The noise is originating from the engine. Once I get it up to speed it somewhat subsides but if you compare it to riding my 49cc its like a Volkswagen to a Cadillac.

RPM
 

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RPM

RPM

New Member
Jun 7, 2009
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Michigan
Hi brandongordon2002,

How many miles on your engine? This engine in the posts above has about seventy miles on it and now makes a noise such as you describe. My 49cc doesn't.

What I think it is on mine and may be on yours is the clutch. I think something might be a little out of round and is rubbing somewhere. You might want to pull the primary cover (opposite side where the chain sprocket is) and see if everything looks ok. I haven't pulled the covers on the sprocket side yet but may eventually.

I'm not really worried about it at this point. I think quite a few of these engines come with 'quirks' from the factory and you have to 'tweak' them to get them running smooth.

While you have the primary cover off put a few dabs of grease on the drive sprocket. Not too much or your clutch will start slipping.

RPM
 
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