Zuma rear wheel locked after overhaul

[KDS4444]

Variator is now off. Rollers are all fine, variator is fine. Clutch also removed. Also seems to be fine. Next is the gear box...

[KDS4444]

Have drained the gear box. The fluid is clear, has no chunks in it, the color of maraschino cherry syrup...

[KDS4444]

Before I open up the gear box...


...Let's assume there had to be a lean seize: I know I was opening up the air jet to try to lean out the fuel, and I am certain (now) that I opened it up too far for its own good, not knowing what the consequences would be. In fact, let's say 100% that's it. It has to be.



My rear wheel is still turning, albeit reluctantly, and in one direction more than the other. Let's assume I have lubricated the cylinder, and that the wheel does turn somewhat (the seize is not total). I want to get the scooter back to running like normal again. Also, let's assume (because it is true) that I did not have a good seal at my exhaust port, and that I now have a new gasket for it which should make a very tight seal (because I do, and it should). What would I have to do now to get it running? Replace the o-rings on the piston? (Remove the cylinder head et al.) Because I am all but certain that this is what I have going on here.


But does this explain the fact that the rear wheel is still turning the piston when the scooter is off? Also, when I turn the variator now, I can hear the piston going "thump thump" inside the cylinder, like it is making a seal in there and "popping" when it reaches the exhaust port. Should it be doing this? Is this a good thing or a bad one? (or maybe it makes no difference).

[KDS4444]

Gear box now open. Nothing unusual inside. Rear wheel turns freely now. Please advise.

[sc00ter]

The rear wheel should spin freely, like any scooter out there, when in the OFF position or while at idle. Even if the engine grenades, it (rear wheel) should still spin freely. You said the wheel spins freely after pulling the reduction box cover off, and the ATF fluid looked metal free, what does it do when you put the cover back on? Side note: Someone said not to use ATF fluid, I agree. Use whats recommended in the owners or service manual. We use 10-30 fully synthetic motor oil.

I still think its a lean seize. You want to look at the side of the piston thru the exhaust port. Spark plug color should also be an indicator. Is it the lovely mocha color? Brite death white? You could also do a compression test. You can "rent" them for free at most major auto parts store. I dont have a service manual handy with the compression specs. If you do a compression test, do multiple (3 or 4) completely from start to finish. Sometimes those things dont always seal 100%, so do multiple test and average the numbers.

One last wild card. There is a chance that running it with an exhaust leak caused a reed pedal to crack/chip. The stock metal reeds hate expansion chamber style exhaust also. The metal reeds will destroy the piston when they fail, and if the damage goes past the piston skirt, your main bearings will be shot as well.

If Zumaforums was still active, you could have found someone 2-stroke savvy in your area easy. Its a FB page now from what I recall. Be warned if you go there! Stupid questions will get stupid answers! Its a trial by fire but as a whole they will eventually reach out and help.

But in a nutshell:
The rear wheel should turn freely when OFF or idling. It should NOT be tight or turn with the motor when OFF or idling.
IF it does, the clutch is hanging up or the variator is not seating correct.
IF the rear wheel is dragging, I bet $5 the reduction gear is not spaced correct. It will bind and drag, sometimes worse when hot.
IF you had a lean seize, there is a chance it might run for awhile again.
BUT STILL find the base/factory settings and set the carb BACK to stock!
IF some old man tells you your scooter is running rich, rev it a couple of times and choke him out with the sweet smell of 2-stroke! Then ride off into the sunset, leaving a cloud of bug killer behind you!
LOOK again at the side of the piston thru the exhaust hole.
LOOK at the plug color and for trash in the plug gap.
LOOK thru the piston hole and see if there is a hole in the top of your piston. A compression test will reveal this as well.

Thats the extent of my powers from across the country. I wish I was closer, but there is SOMEONE in your area, you just have to find them. I've met some interesting people thru scooters and bicycles. I help 3 people with cheap transportation needs. 2 scooters that are their only transportation and one guy with just a bicycle. Got so tired of working on old, worn out bicycles I gave him my Fairdale Taj 26". $500 to me is like $5000 to him. He pays it forward as much as he can.

Again, let us know your findings. And fingers crossed/thumbs pressed (German saying) that its something simple!

[bandito2]

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]

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]

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]

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]

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]

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]

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!

[KDS4444]

Time for an update!


After cleaning up my piston and cylinderI ordered replacement gaskets for the head and base. Finally, a few days ago they arrived! Yesterday I went down to the scooter and installed them. I made sure the cylinder head was very smooth and that my gaskets were seated correctly. I got the piston back in the cylinder (NOT easy!) and got the head on top of the cylinder. I cranked down the four bolts that hold the cylinder and head in place. I put the spark plug in, I reattached the electrical connection to it. I re-attached the air filter (also NOT easy). I put the crank case cover back on the crank case. I put my key in the ignition. I said a prayer to some heathen gods. And I gave the kickstart a good solid push.



Nothing.


I checked the kill switch (that one has fooled me before) but it wasn't set to kill. I tried the kick starter a few more times. Nothing.


I checked the spark plug— apparently I hadn't tightened it down, had just put it in finger tight. I was sure I had found my problem! I tightened it down, re-attahed the electrical cable to it, and jumped on the kick starter.


And still... Nothing.


The kick starter is moving the piston in the cylinder, and I can smell gas, but there isn't anything like ignition happening inside there at all. I didn't mess with anything electrical other than removing, cleaning, and reinstalling the spark plug. But I am not getting even a glimmer of life from it now. It's like everything is in place, but the damn thing has chosen not to cooperate with me any longer.


Got any thoughts on that? I am exhausted and it is late and I am going to bed now. So, so disappointing.

[sc00ter]

Just got in from work-in the rain! Yuck! So I'll give you a quick idea. Are you sure you are getting spark? Hate to say it, but if we have that problem and suspect spark-someone holds it while the other person hits the starter or kickstart. It will wake you up! You will know you have spark! You can also use a spark tester but I have terrible luck with them.

Next up, compression test. There is a chance you broke a piston ring. That would make the compression to low. Or something WAS wrong with the piston. Did you remove the reed cage? If so, did you inspect the reeds? I don't think reeds are you problem but it could happen.

Make 100% sure you didn't pinch the oil supply line when putting the shroud back on! Just double check its not pinched! That will cause problems later once it gets running.

Last thing I can think of. Make sure nothing is stuck in the spark plug gap. I sold a Zuma not long ago and the guy called me saying it suddenly quit starting. Ran great, then never started. Turns out is was a piece of something in the plug gap. Knocked it out and it ran great again!

That's all I can think of right now. Good luck and keep us posted!

[KDS4444]

Let's say the piston rings are probably fine— I was very careful about inserting the piston into the cylinder, and did not force it in, and I never removed the rings from the piston, so I consider a piston ring failure to be pretty unlikely. I also had a good look at the spark plug when I removed it briefly before tightening it down into the cylinder head, and it was clean. The fact that I am smelling gas suggests to me that I am getting compression (probably), but just no ignition.


Let's also say that I test my spark plug with a multitester, and I find nothing wrong with it. And let's say I test its spark by removing it from the engine block and grounding it out, but find no spark when I use the kickstarter. I have not done these things yet (I will very soon) but my sense is that this is what will happen when I do.


And lastly, let's keep in mind that none of these things are related to my original problem, so whatever the problem is now, it has to be the result of something I must have done in the course of trying to smooth out the piston (i.e., removing the cylinder, replacing the gaskets, etc.).


If any of that is helpful, let me know. Will let you know what happens with the spark plug test later today. The beat goes on. La di da da di, la di da di da.