stuck engine on Bravo

I've heard a lot of different ways to free a piston. Most of which I know cant be right. If someone who has done this before could explain how have done it in the past that would be great. Please dont respond if you dont know what your talking about.

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Re: stuck engine on Bravo

The engine could be stuck by the piston being stuck in the cylinder or the crankshaft is rusted and frozen or both of these.

Hopefully you'll get lucky and it's only the piston stuck in the cylinder.

There are several different ways to "unstick" a piston, most good. Here is the one I use.

Buy a bottle of Marvel Mystery Oil at a local auto parts store.

Remove the spark plug and elevate the front of your moped so oil can run down around the piston. Pour a couple of teaspoons of oil into the spark plug hole and replace the spark plug just finger tight .

Let it sit overnight or at least an hour or two.

After letting it soak and with the bike now level and on it's center stand, remove the spark plug and try pushing down on the pedal with your foot to see if it will break free. If that doesn't free it up put a 24 mm socket and ratchet on the front pulley's large flat hex head nut and see if you can turn the pulley Counter clockwise (left) to turn the engine and see if the piston will break free.

You can also push on the ratchet handle with your foot or tap it with a hammer.

Work the pulley back and forth a bit and then try it again counter clockwise.

If it doesn't break free try adding a little more oil and letting it soak again and then repeat the pedal push or ratchet/socket method.

You can also get a round wooden dowel a little smaller than your spark plug tip diameter and insert it in the spark plug hole and tap the dowel with a hammer to see if you can gradually force the piston to move.

Alternate the dowel and using the foot pedal or socket to turn the engine.

Hopefully it will break free. I also sometimes use ATF tranny fluid in a pinch.

You can also use the "Search" feature and search for "unstick engine" to see what turns up.

Good luck

Re: stuck engine on Bravo

Zane,

You can do the steps that Zippy suggested. If it doesn't work, then use a butane welder to heat the engine head. And procceed to use Zippy's suggestion- just don't overheat. Try heating it for 10 seconds at first, then try 20. But don't exceed 40 seconds.

EK

Re: stuck engine on Bravo

See Ya Moped Army /

If all else fails, take an old spark plug socket and place it on the head of the piston and bang the crap out of it with a hammer or mallet until it moves. This is a last resort if all else fails. Once you do this, you will most likely have to replace the piston and rings. Just be careful not to hit the face of the cylinder or the cylinder walls with the hammer or spark plug socket. If you have to resort to this method of freeing the piston, there's a very good chance that the crank bearings are also rusted and will need to be replaced, along with all the the oil seals and case gaskets (if applicable).

Re: stuck engine on Bravo

_If all else fails, take an old spark plug socket and place it on the head of the piston and bang the crap out of it with a hammer or mallet until it moves. _

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Larry -

I'm not really understanding this method. I know full well that you know your way around old peds, so I must be missing something.

Dave

Re: stuck engine on Bravo

See Ya Moped Army /

Dave, it's the same theory as placing a wooden dowel through the spark plug hole and hitting it with a mallet, except that you remove the head and use a spark plug socket in place of the dowel. You then pound on the end of the spark plug socket wit a hammer.

Re: stuck engine on Bravo

Ahh - OK!

I didn't know you took the head off, was wondering how you got that socket through the spark plug hole!

That clears it up, thanks!

Re: stuck engine on Bravo

I admit I have no idea what i'm doing. so I had the engine off of the bike to begin with. I put a cork in the exauhst and poured marvel mystery oil in through the spark plug hole. After a day it was able to seep around the piston and out the intake. If i put a wrench to the hex not on the pulley it unscrews thew hex nut.

What do I do now?

check out the picture of the recently detailed bravo! yes, it has been detailed. It looked a lot worse before.

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Re: stuck engine on Bravo

turn the ratchet the other way just try not to strip the threads on the nut or pulley

Re: stuck engine on Bravo

Tried. its not going anywhere. now what?

Re: stuck engine on Bravo

If you haven't already tried it, use the wooden dowel through the spark plug hole and try hammering the piston downward.

You can also remove the head and use a larger wooden dowel to try to hammer the piston down.

You can alternate using the dowel and hammer and the rachet on the 24mm hex nut rocking it back and forth if it will move.

If all else fails, use an old spark plug instead of the wooden dowel as MopedLar suggested and see if you can pound that piston down. You will most likely have to replace the piston after the spark plug method.

I have new rings, piston and cylinder kits available if it turns out you need any of these.

Good luck.

Re: stuck engine on Bravo

After being sidetracked, i am returning my focus to the Bravo.

I took the head off and it now turns over. Unfortunately the piston is still siezed to the cylinder and the whole cylinder moves up and down with the piston. see picture attachment. Hammers dont seem to be helping. Any thoughts?

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Re: stuck engine on Bravo

it's practically out.. make sure a ring didn't pop out into the exhaust port and is stopping it.

Support the cylinder while pounding away.. and don't pound while the crank is straight up and down or you may screw up the connecting rod bearings.

Re: stuck engine on Bravo

hammering is only turning the top of the piston into filings,

Re: stuck engine on Bravo

im looking at that pic and it seems that the crown is the only thing left to come out.

can you see the ends of the piston wrist-pin? Can you get it out?

If so, do it .. and then take the cylinder over to to a bench and push the piston back up the cylinder a little ways.. and find whatever it's getting jammed on.

Re: stuck engine on Bravo

Unstuck. I wedged 2 2x4s between the cylinder and crank case and stretched them across an open bucket bucket. with an industrial 1'' thick bolt and a sledge hammer I procceded to bang the crap out of it as hard as i could. 50 or so hits later the engine fell into the padded bucket. So who here has the neccesary vespa engine rebuild parts for sale?

Re: stuck engine on Bravo

I have cylinder kits for $125 plus shipping.

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