MZ/MuZ Riders

Morning all, I have a TS125 with the piston seized in the barrel, its near the bottom, so a lot of the piston is where the inlet/exhaust ports are so I cant get penetrating fluid to stay in. I have given it a good bashing with a steel rod but still no movement.

Anyone any good ideas???

Shaun

Shaun, 'a good bashing with a steel rod' might not be the best idea. Be careful not to damage bearings and/or deform the piston. Not sure if you can get the studs out in that bike, but if you can, it might help. Avoid bending the conrod though, but maybe you can make some contraption to push the piston out, while making sure it is not in BDC. You could also try to heat the barrel while lifting it from the crank case. And then when it's hot, spray something (WD40?) onto the piston to cool it down & make it shrink.

Good luck!

Hi Puffs, thanx for the reply. I wasn't bashing too hard as I was worried about damaging con rod! Two of the studs came out as the nuts were solid, so I might try to get the other two out and see if I can get some purchase on it that way. Not too worried about damaging piston as a new piston set is only £46.00 but I am worried about damaging con rod/small end!

Thanks

shaunlacy wrote:Morning all, I have a TS125 with the piston seized in the barrel, its near the bottom, so a lot of the piston is where the inlet/exhaust ports are so I cant get penetrating fluid to stay in. I have given it a good bashing with a steel rod but still no movement.

Anyone any good ideas???

Shaun

It's amazing (to me ) how a seized piston can be so tight!. I also resorted; against my better judgement; to bashing with an axle from a wheelbarrow. When I finally got it out, the only marks in the bore were from water damage and where my hammering contacted the bore No indications of the seizure in the bore. So I second Puffs recommendation for the reasons he mentions and to anyone else who may be reading, try and use wood. * The other thing is take notice of your piston size stamped on the crown before you obscure it with hammer blows.

Optimize your work conditions.: if the engine is in the bike, take it out so you have plenty of room.
Can you rotate the crank so as to raise the cylinder out of the crankcases then jamb some wood under the cylinder tho stop it slipping back when you apply pressure

If you can block off your inlet holes with greased rags stuffed with cooking foil you may be able to soak some WD 40 or my preferred diesel into the contact area.
If you can remove all the cylinder studs, you may be able to twist the cylinder. As well as little end and conrod,you have to be careful to protect your big end from debris as you may snap a ring; If you're not planning on splitting the cases anyway .
These are all desperate options and ran through my mind when I was faced with a similar problem.

Good luck

I had a very similar problem with one of my MZ's when I got it.
13 years off the road, not only was the piston well and truely seized, but it appears it was seized due to water ingress. Luckily the piston was half way up the barrel and covering the ports, otherwise the crank would be toast.

However.. I had to hammer the crap out of it. The piston was 3rd oversized anyway and upon getting the two seperated, was pretty well scored. The barrel also had a lot of corrosion in the form of water concentration utop the piston that only a 1mm re-bore would remove, esspecially near the frontal wall.

New piston and re-bore was required.. At least for me, anyway..

Well, I managed to get all of the studs out, but it still isn't for budging, worried about twisting too much, don't want to bugger big/small end bearings!

Will a gas torch on the barrel help, or will the piston heart up quicker?

Be careful with rotating, that way you'll likely bend the conrod. Anyway, at the end of the day (so that's after your re-bore & new piston) its a good idea to check it is still straight (using feeler gauges left & right, without rings on piston). The middle part of conrods is often not hardened.

But now that you can lift the barrel, you're sure it isn't in BDP. Make a contraption using ends of thread (with a nut & a big sturdy ring on the base side, to prevent damage) and a cross bar on the top side, to push down the piston (with a big bolt & a safer below it). Load it, firm but without overdoing, and if it does not go, try the trick with a gas torch on the barrel. The piston is inside, and should heat up slower. Keep the load on, and then cool down the piston. That should make it move.

Did you put WD40 through the inlet? Pistons are widest at their skirts, and that's probably where it sticks.

And if none of this works, maybe try dirtsurfer's diesel soak, for a week.

Cheers puffs: Difficult to soak it cos of inlet/exhaust manifold, but I like the idea of a bolt/screw to force piston down. I think I can make something to that with.

Be back with the results soon . . . . .

got the scissor jack off my Landrover and created a screw - still no movement, blanked inside the barrel with a wooden insert so as not to damage barrel & piston!!!! AAAAAAgh!!!!

Broke Jack! other half furious lol! oh well, next idea . . . . .

I would have thought something else would give before your jack broke. Whip the engine out of the frame and start pounding. Tell her you love her

bolt it down in a milling machine and use a cutter to whittle it out of there
just make sure you miss the con rod small end area

I too am baffled it was the jack that failed first. I would expect the frame to go first, and at least be bent in some odd way. Or the bridge in the barrel below the inlet. Anything...
Those blocks of wood could be 2", so close to 58mm: are you sure you're not at TDC? If you want the piston to move, the crankshaft should be somewhere mid stroke, best roughly half-way between BDC & TDC.

Suggest to spray WD40 onto the piston through the inlet, and from any other side you can reach it. Support the barrel on something suitable (mid stroke), best below the overflow ports at the sides (the bit below the inlet channel is weaker), making sure it is supported evenly at all sides, and straight. This to prevent bending the conrod, although that might already be bent after the exercise with the jack. Then heat the barrel, cool the piston & hit it. Or load the piston as outlined earlier.

Do you have any idea why the piston is stuck this way? Is it just corrosion, or is there maybe some other mechanical reason? If it's corrosion, how bad does the lot below look? Big-end & main bearings still OK? If you need to replace those anyway, no point in pussyfooting & consider to sacrifice the conrod. At any rate, that seems preferable over bending the frame. But before you do anything drastic, think carefully.

Hi, definitely not TDC, it dropped about 3/4 of an inch onto blocks, If i thought I could get e replacement barrel I'd cut it off but they look rare as rocking horse .....
That jack lifts my Landrover, so at least two tons of force applied before it buckled . . . scratches head . . .

On the plus side just been out for a good long ride on another bike so am chilled now, will look at it later in the week!

shaunlacy wrote: . .

On the plus side just been out for a good long ride on another bike so am chilled now, will look at it later in the week!

A good ride helps to clear the mind

Can you see where the bore is scored? If so you could drill some holes in the crown of the piston close to the side. Then inserting a narrow cold chisel or use a dremel to work away at the piston and rings in the bound area