Zuma rear wheel locked after overhaul

[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.

[sc00ter]

If you ground the spark plug to check for spark, watch out if there is still gas/vapors in the cylinder-it will turn into a flame thrower! Get a cheap spark tester from a auto parts store.

Another thing, did you point the arrow on the piston toward the exhaust port?

Cracked reed pedal will also prevent it from starting. The reeds don't like being ran with an exhaust leak.

After you verify your'e getting spark, you could always use a dash of starter fluid to help bump it over. If it still won't start you'll need to do a compression test.

I wish I knew someone 2-stroke savvy in the L.A. area. Know a bunch of lowrider car guys and a few bands, but no moped/scooter guys out that way to send help. I kinda regret tossing that low miles stock top end in the recycle bin now. There is Myrons Mopeds in Fullerton. Shaun is a good dude and knows his 2 strokes.

[KDS4444]

Your offer to put me in touch with a person out here who could help me is very generous. There is nothing like a personal network connection to actually get things done! As it is, though, it seems like I am on my own for now.
I tested the spark plug, and had some surprises:
The plug tested out just fine as far as resistance goes, so I grounded it and cranked the kickstarter. It sparked! A bright blue-white spark came shooting right across the gap, just as it should! I was pleased, and put it back in the engine. This time, there was something like turnover happening. The engine didn't exactly catch and start turning over on its own, at least not at first, but I tried cranking it again a few more times and one of those times the engine actually ran for a second or two on its own!
But it didn't sound right. It's hard to put my finger on it, or describe the sound itself, but it didn't sound the way I know it should. It also wouldn't take off like that a second time for me. But it shows me that I am getting ignition. So my guess now (and probably yours as well) is compression. If I have a leak anywhere around the cylinder base, head, or spark plug itself, this is the kind of response I might get from the engine. "Yay, fuel! Spark! Ignition! Move that piston! Oh, wait, not enough compression.... Sorry! Goin' down!" I've had a compression issue once in the past, and it sounded like a giant dragon fly was inside my engine— it was the sound of compressed air escaping around the cylinder (oh and yes, quickly, I am sure the piston is facing the correct way, I was VERY careful about that! The arrow on the head of it points towards my exhaust port!). This didn't sound quite like that, but it could certainly still be the problem here.
Or, as you said, it might be the damn reed valve. That's one part I have not taken out and had a look at yet, esp. because it isn't terribly accessible. But as you said a cracked reed would also prevent me from getting proper compression in the cylinder. Are there tests I can do to see if my cylinder is leaking somewhere first? I can also try tightening my cylinder nuts down just a bit tighter and see if that helps at all. But I feel good knowing that at least I don't have an electrical problem and that my spark plug is working as it should.
Thank you for continuing to engage me here. I really appreciate the willingness to keep with me and help me try to solve this problem. That means a lot.
....
Later that evening...
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Okay, I went down and tightened up the spark plug and cylinder nuts again, and gave the kickstart a go. The engine caught! I was amazed! It still didn't sound right, but it was running! I let it run for 3 or 4 seconds, and pondered taking it off the kick stand and driving it around the block. But then things suddenly changed: the speed of the piston in the cylinder picked up, and the sound coming from the engine became much more raspy and loud. I shut down the engine immediately. The sound was unlike anything I have ever heard before coming from the scooter.
It seems that I am finally getting compression, at least briefly, inside the cylinder. But the rasping noise? Would a cracked reed valve petal make a noise like that??
One more thing: I noticed when I put my air filter box back on that there were some cracks in the elbow joint where it attaches to the carburetor. I assume I will now need a new air filter box. The cracks mean that some unfiltered air is now able to get past the filter and go straight into the carburetor. Would this be causing the sounds I heard?

[sc00ter]

A cracked/broken air box is a death wish to ANY motor, but its extra bad for a 2-stroke because they are so sensitive to everything being correct. Pattern replacement air boxes are the way to go. Scootertuning.ca and sometimes Scooter Swap Shop have them for good prices. Or get a OEM one for a bit more. Don't be tempted to get one of those pod style air filters, they require jetting changes. Stick with stock or pattern replacement. If its just the elbow that looks cracked, that's normal. The rubber coating on the elbow flakes from age/heat and makes it looked cracked.

Be careful when tightening down the head screws. I forgot the torque vale but it needs to be done at the correct torque/evenly so the head doesn't warp.

It you had a broken reed it wouldn't even start. So your'e fine on the reeds. Plus, the reed cage is a PITA to seal when re-installing. So any reason not to remove it is good.

That sound you hear is a new one to me. Never had a noise like that.

My Zuma is still in a million pieces. But typing to you has kinda motivated me to get it sorted and put back together.

Again, good luck on figuring it out. Asked around to the lowrider guys and they don't know anyone who messes with "mopeds". Worth a shot though.