Zuma rear wheel locked after overhaul

bandito2 · 04-02-2020, 01:23 AM

If the wheel turns when you turn the motor by hand (or by turning the wheel it tries to turn the belt/variator&motor) then the clutch is definitely holding/stuck in some way keeping it engaged. Open up the clutch to see if any of the shoes (or any broken pieces causing it to bind) are stuck against the bell. Betchya if you free the clutch, the wheel should turn easier because it will not be engaged trying to turn the belt which is connected directly to the variator which is directly connected to the engine crankshaft. With the bike NOT running and up on the center stand, turning the rear wheel will turn the bell through the final drive transmission as normal but should not be trying to move the belt because the clutch should be disengaged.

Fix your clutch!
(but you may have possibly done some engine damage too... which is a separate issue apart from the clutch)

Oh, and it should be easier to push the scooter (if the clutch is still stuck) by removing the spark plug... then you won't be fighting the engine compression of the piston stroke.
(and I don't even own any 2 stroke stuff, but did once upon a time... ultralight aircraft engine. It was a thing of beauty; Rotax 503 electric start+ pull start, 2 cylinder, dual carb, dual ignition)

KDS4444 · 04-02-2020, 10:22 PM

So when I reassembled the gear box and re-attached the clutch, v-belt, and variator, the problem continued. But I figured out what was causing it: for some reason, when I screw down the nut on the clutch bell, it causes the rotation of the rear wheel to rotate the entire clutch (as though I had the engine on and was driving). When I loosened this nut, the bell stopped rotating and the rear wheel could rotate freely (and didn't cause the piston to move). It seems something about my clutch and its bell is (right now) causing it to be continually engaged, but whatever it is, it isn't the tightness of that nut alone: I know that the nut has to be screwed down SUPER tight to ensure the bell doesn't come loose inside the crank case! Maybe I am missing a washer somewhere (don't remember there being one to lose, though).

But whatever that problem is, I am considering it minor (for now) compared to the weirdness I experienced while driving a few days ago and the way my engine died in a lean seize on the way home. Haven't opened up the cylinder or tried to remove the piston yet, but am thinking maybe that is going to be next. Any advice on that is welcome!

sc00ter · 04-02-2020, 11:19 PM

Nothing in that transmission is higher than 40nM. We set both cluch bell nut and the variator at 40nM. I dont have a service manual to see is there if there is a washer, but you could always go to Cheap Cycle Parts and look at their exploded parts diagram. See if everything looks correct. Just looking inside the exhaust port with the piston forward, so you can see the side of the piston, will tell you if you had a lean seize. Spark plug is also a good indicator.

Sometimes, when you have a lean seize at speed, it will reveal everything thats wrong in the transmission.

Off the top of my head, I have no idea why tightening the bell down would cause the symptoms you described. Will think about it in the morning.

I have an ebike and my front wheel caught a transfer on the road (from milling and paving) and spit me off the front at 22mph. I hit the ground HARD, and as a bonus, got a chunk of my hair torn out! I need a bicycle helmet! Road rashed my knee and elbow, have a huge rash on my head and a chunk of hair missing. Ouch! Anyways, will give it some thought in the morning.

KDS4444 · 04-03-2020, 05:43 PM

DUDE! YOU NEED A BIKE HELMET! People don't realize just how dangerous a "simple bike" can be! At 22mph you are almost asking to be killed! And I still NEED YOU!

Tell me if this is what a lean seize looks like...

https://photos.app.goo.gl/SywYSJ2Z9EYyYVKG6

Aw, hell, I know what a lean seize looks like by now, and I know this is it. BUT! I have now polished that piston up, and though some of the scratch marks are still visible, I'd like to know if you think it might be at all worth my time to go ahead and polish up the cylinder as well, add new gaskets, put it all together again, and hope it will run. Here is a photo of the polish job on the piston:

https://photos.app.goo.gl/6Bm4fwrTvpCojPYMA

Stay off that bike until you have headgear!!!

sc00ter · 04-03-2020, 08:25 PM

Actually, no. That piston looks normal, at least in the pics. I had a lean sized piston I saved for an example but I think it got tossed when the garage was cleaned.

If in fact that was a soft seize, it was super soft. I had one once going to work. I pulled over, got it started, choked it (I run manual chokes) to flood/cool it down and re-adjusted the carb. It was 26 degrees out and the scooter carb was set for summer weather. That scooter never seemed to notice, though looking thru the exhaust port you could see one good, deep scratch.

There is a chance that when, whatever caused the transmission failure, it perfectly matched a lean seize in symptoms. Its just not normal to have the clutch constantly engaged like you describe when the scooter is OFF or at idle.

And yes, I can still go to my local bicycle shops. They are practicing "social distancing" but I may go Sat. and look for a helmet I like. The ugly rash and bald spot from having my hair torn out meaning I'll have to wear a do-rag to try them on. Looking into a Nutcase brand.

KDS4444 · 04-04-2020, 09:58 PM

So those scratches on the piston don't seem all that serious to you? Gosh, I hope you are right! Although if so, then my problem, whatever it was, still remains... Do you think, then, that the problem all along has been something inside my crank case? This would explain why my rear tire wouldn't move after the second breakdown, I guess, since if the clutch bell somehow got "locked" to the clutch proper it would have become very difficult to turn the wheel (which, as said, it was). The symptoms certainly seemed to fit with a lean seize, but maybe not?

Okay, now I have to go back down to the scooter and have a more serious look at that clutch and figure out why it was staying engaged. If nothing else, I have at least given my cylinder and piston a thorough cleaning and overhaul and new gaskets, perhaps forestalling possible future problems there! (though let's be honest, it's a 19-year-old machine, and things are gonna give out on it from time to time— but it's all I got to drive!).

...Sometime later...

I think I have the clutch thing figured out. I had removed the bell and was looking at the big nut that holds the rest of the clutch together. It seemed to have circular wear marks on it. I thought this was strange. And when I screwed the bell on tight, it seemed like this is where the bell was coming into contact with the rest of the clutch.

Well, it WAS where the bell was coming into contact with the clutch: because I had not screwed that nut on super tight when I had finished replacing the springs on the clutch shoes, and that nut was slowly coming loose inside the crank case, pushing it up against the bell.

I feel a little like an idiot here, but bear with me as I tighten that nut down, reassemble the clutch/ variator, re-seal the cylinder, lube it up, and see if it runs. Oh, and return the air jet to factory specs. Of course. Wish me luck!

sc00ter · 04-05-2020, 12:17 PM

So it turned out that big, thin nut that holds the clutch assembly together came loose? If so, you found out what was going on. There is a special tool that locks that whole assembly together. The clutch springs and/or the torque (contra) spring can be changed without the tool, but the tool makes it a easy!

You can get the socket for that nut from buggypartsnw.com. They sell a dual sided socket that has both 39 and 41mm. We get individual sockets from Northern and have the inner bevel planed off for a better fit, but the buggyparts one works very well. Forgot the torque on that nut though.

Side note: I never would have removed the cylinder if there were no scratches on the exhaust side of the piston or if there was not a hole in the top of the piston. That was just extra, unnecessary work. At least you now know the top end is all good.

Get it back together correctly and let us know if all is well. Zumas are quality, tank like little scooters. I've owned at least 6 in the past, 2 of those pre-bugs. You have a bug-eye. Good luck getting her purring again!

04-02-2020, 10:22 PM	#2
KDS4444 Join Date: Mar 2020 Location: Los Angeles, CA Posts: 28	Clutch! So when I reassembled the gear box and re-attached the clutch, v-belt, and variator, the problem continued. But I figured out what was causing it: for some reason, when I screw down the nut on the clutch bell, it causes the rotation of the rear wheel to rotate the entire clutch (as though I had the engine on and was driving). When I loosened this nut, the bell stopped rotating and the rear wheel could rotate freely (and didn't cause the piston to move). It seems something about my clutch and its bell is (right now) causing it to be continually engaged, but whatever it is, it isn't the tightness of that nut alone: I know that the nut has to be screwed down SUPER tight to ensure the bell doesn't come loose inside the crank case! Maybe I am missing a washer somewhere (don't remember there being one to lose, though). But whatever that problem is, I am considering it minor (for now) compared to the weirdness I experienced while driving a few days ago and the way my engine died in a lean seize on the way home. Haven't opened up the cylinder or tried to remove the piston yet, but am thinking maybe that is going to be next. Any advice on that is welcome!
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04-03-2020, 05:43 PM	#4
KDS4444 Join Date: Mar 2020 Location: Los Angeles, CA Posts: 28	Holy mackerels! DUDE! YOU NEED A BIKE HELMET! People don't realize just how dangerous a "simple bike" can be! At 22mph you are almost asking to be killed! And I still NEED YOU! Tell me if this is what a lean seize looks like... https://photos.app.goo.gl/SywYSJ2Z9EYyYVKG6 Aw, hell, I know what a lean seize looks like by now, and I know this is it. BUT! I have now polished that piston up, and though some of the scratch marks are still visible, I'd like to know if you think it might be at all worth my time to go ahead and polish up the cylinder as well, add new gaskets, put it all together again, and hope it will run. Here is a photo of the polish job on the piston: https://photos.app.goo.gl/6Bm4fwrTvpCojPYMA Stay off that bike until you have headgear!!!
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04-04-2020, 09:58 PM	#6
KDS4444 Join Date: Mar 2020 Location: Los Angeles, CA Posts: 28	Do you think, then... So those scratches on the piston don't seem all that serious to you? Gosh, I hope you are right! Although if so, then my problem, whatever it was, still remains... Do you think, then, that the problem all along has been something inside my crank case? This would explain why my rear tire wouldn't move after the second breakdown, I guess, since if the clutch bell somehow got "locked" to the clutch proper it would have become very difficult to turn the wheel (which, as said, it was). The symptoms certainly seemed to fit with a lean seize, but maybe not? Okay, now I have to go back down to the scooter and have a more serious look at that clutch and figure out why it was staying engaged. If nothing else, I have at least given my cylinder and piston a thorough cleaning and overhaul and new gaskets, perhaps forestalling possible future problems there! (though let's be honest, it's a 19-year-old machine, and things are gonna give out on it from time to time— but it's all I got to drive!). ...Sometime later... I think I have the clutch thing figured out. I had removed the bell and was looking at the big nut that holds the rest of the clutch together. It seemed to have circular wear marks on it. I thought this was strange. And when I screwed the bell on tight, it seemed like this is where the bell was coming into contact with the rest of the clutch. Well, it WAS where the bell was coming into contact with the clutch: because I had not screwed that nut on super tight when I had finished replacing the springs on the clutch shoes, and that nut was slowly coming loose inside the crank case, pushing it up against the bell. I feel a little like an idiot here, but bear with me as I tighten that nut down, reassemble the clutch/ variator, re-seal the cylinder, lube it up, and see if it runs. Oh, and return the air jet to factory specs. Of course. Wish me luck! Last edited by KDS4444; 04-05-2020 at 12:59 AM. Reason: New info
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04-05-2020, 12:17 PM	#7
sc00ter Join Date: May 2017 Location: Norfolk, VA Posts: 530	So it turned out that big, thin nut that holds the clutch assembly together came loose? If so, you found out what was going on. There is a special tool that locks that whole assembly together. The clutch springs and/or the torque (contra) spring can be changed without the tool, but the tool makes it a easy! You can get the socket for that nut from buggypartsnw.com. They sell a dual sided socket that has both 39 and 41mm. We get individual sockets from Northern and have the inner bevel planed off for a better fit, but the buggyparts one works very well. Forgot the torque on that nut though. Side note: I never would have removed the cylinder if there were no scratches on the exhaust side of the piston or if there was not a hole in the top of the piston. That was just extra, unnecessary work. At least you now know the top end is all good. Get it back together correctly and let us know if all is well. Zumas are quality, tank like little scooters. I've owned at least 6 in the past, 2 of those pre-bugs. You have a bug-eye. Good luck getting her purring again!
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