Moby engine disassembly questions

As you might have read, I did some shoddy repair work and allowed a small chunk of metal to break off my carb, get sucked into my engine/crankcase and seize it up. Now I'm faced with taking the engine apart to retrieve that chunk and assess the damage. My question is, is the procedure really as complicated as the service manual makes it sound? Do I really need to remove the flywheel, magneto, and variator just to peek inside the crankcase? Should I replace all the gaskets like it says? Which of the special tools can be substituted for?

I'm starting to feel like I'm in way over my head, and that I should have shelled out for a new TFR or something. I wanted to do a little work, enough to understand how everything works, but I mainly wanted to ride.

Re: Moby engine disassembly questions

i dont know much about these type of engines but if i were you i would take everything apart. sure it might sound hard but its not that bad. you just have to make sure where all the wahsers and everything goes. take pictures or take notes if you must. as for the gaskets, i dont feel its needed to replace them unless they are worn badly or get damaged in the process. good luck

Re: Moby engine disassembly questions


At this point, I'd inspect the top end first - it's easy enough to do.

Pull the top motor mount bolt, and let the engine pivot downwards a bit. Put something beneath to support it. Watch the cables & lines, don't stress them.

Remove the nuts affixing the head, and the head itself. Be careful with the head gasket, and you'll probably get away with reusing it. It should be a wafer of aluminum.

If you're in luck (I'm stretching the meaning of the word) you'll see the damage.

You mentioned that the flywheel is immobile. Is it totally locked soild, or can you get just the slightest wiggle out of it? If there is some wiggle, then the bottom end is probably OK, and it's just the piston & cylinder that are seized.

But to answer your original question - yes, you need to pull everything off to get into the crankcase. A puller that does both the point cam and the flywheel is available from for about $25. That odd nut on the magneto (square drive) is a left-hand thread, so watch it.

On the bright side, you probably don't have to make a piston stop to get the nuts loose. Small consolation, I know.

Re: Moby engine disassembly questions

there's not much inside a 2-stroke crankcase.. you have a crankshaft / connecting rod and that's about it.

you can look inside the crankcase by removing the head and then the cylinder. The resulting gaping hole allows plenty of access to get in there and fish around.

Splitting the engine's case completely apart is what they're talking about.. flywheel, magneto etc would need to be removed so the case halves canbe pulled apart. This might be needed if main bearings were to be replaced or some such major surgery.

My guess is that pin is probably stuck in the intake port, jamming the piston against the port opening.. Or jamming the piston in some other way. ..and, if so, repair doesn't even involve the crankcase directly.. Or it might be inside the crankcase jamming the crankshaft .. with a bit of luck you might pluck it out through the large access hole provided by only removing the cylinder.

Set up a workplace.. clean.. a table top with enough space for tools and disassembled parts. get a 6-pack of beer and draw up a plan of attack.. and take your time.. this stuff is a lot easier when you're relaxed and comfortable. And once you've removed a head and cylinder you'll see how simple it all is..

Re: Moby engine disassembly questions

Thanks for the advice guys. My thoughts of cutting my losses and selling the bike off for cheap are all but gone now. I think I'll try joew's technique first, as it has the twin advantages of sounding easier and involving beer. I hope I'll be able to see into the crankcase without removing the piston from the con rod. If not, it's on to the more involved ways.

Bill, I assume that if you're going to call me A-bomb, I can call you by your first name and not "Legendre" now!

Re: Moby engine disassembly questions

be neat and keep track of removed parts (keep notes, label parts with masking tape, etc).

The engine is somehow jammed on the pin.. flywheel won't move at all. (?) If so, that pin may be caught between cylinder and piston. This will prevent slipping the cylinder up and off the piston/connecting rod..

So, first find the pin determine exactly how it's jammed.

Last resort in such a situation is hammering the piston's crown and driving it downward to free it.. Muscle and a hammer could damage the engine (crank bearings, etc) more than the slide-pin being jammed did.. ask for advice and opinions once you find the pin.

Re: Moby engine disassembly questions

Ha ha.. I'm not really sure why I called you that.. Something about A with the bombed motor. Anyway, all in good humor.

I know you're going to fix this thing, and it will be better than when you started. If things are really bad in there, you can always consider sending the motor to Smitty, or maybe MoPedLar.

When you said 'get into the crankcase', I immediately thought you meant splitting the cases to service the bottom end. I think joew's advice is the answer you were actually looking for.

As far as calling me Legendre, that's only required if I'm in the company of zombies, or other undead.To them, it's strictly Dr. Legendre - and I don't want them getting any ideas of their own.

Last time they did, I was thrown bodily from the parapets of my castle. That was nearly 75 years ago, and I'm still pissed about it. Never trust a zombie, ever.

Re: Moby engine disassembly questions

yeah like everyone said.....

removing the 4 head bolts will be enough to see where the problem is.

I have never taken apart a crankcase, and never plan on doing so. there are plenty around if you are resourcefull.

p.s. I have cylinders and pistons.

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account