TS250/1 Piston

[David Penwarden]

Hi, new to the MZ Riders club.
I bought a 1978 TS250/1 recently that has stood for 30+ years, 22,000 miles filthy but is cleaning up OK. I have started to look at the engine, piston & bore are worn (standard size 69mm) so will get the cylinder re-bored. I am looking for advice on pistons, are there original pistons available? or are there recommendations/experience of alternatives.
Thanks for your help.

[Keith Wilson]

Yes they are available.try these shops.
Gabors mz laden
Gusi motorcycle parts
Mz zweirad Schubert
New old stock and pattern.
Hope this helps Keith

[Ollie Harris]

I think the original brand was Megu, which might help when searching online. “Almot” are considered to be good aftermarket pistons. Some of the cheap aftermarket ones are really bad

[David Penwarden]

Thanks Keith and Ollie, I will have a look at those suppliers.

[John Mitchell]

I have one if your stuck

[David Penwarden]

Sorry for the delayed reply, I have had the bike running now for a few weeks and completed c.370 miles and all seems OK at present. I ended up with an Almot piston with the bore done to give the standard clearance, on the face of it this looked like a tight clearance but is running in well.

[Dick Green]

Similar issue here. Need a rebore and new piston.
Standard is69mm and stamped 68.96
Am going for 70mm but what should i get the cylinder bored to
Any help please

[David Penwarden]

I would use the standard clearance, 0.04mm. So if you use a 70mm piston the bore will be 69.96mm finished size. Who ever is doing the rebore should measure the skirt diameter to check the marked size. I have run 600 miles since the rebore on my engine with a 0.04mm clearance and all seems fine. I am always careful with running in.

[Luke Duller]

1st oversize for a TS250/1 is 69.50mm. There’s no point in removing more than you need to so, assuming you don’t already have a 70.00mm piston and the bore will clean up at 69.50mm, I would buy a 1st oversize rather than going as far as 70.00mm.

FWIW, I specified 0.05mm clearance for mine. Unfortunately, the RAM piston I had bought turned out to be poorly-machined scrap and so I replaced with an Almot. This was discovered *after* I had the barrel rebored and the Almot was ever so slightly smaller so the final clearance was closer to 0.08mm! Not far from MZ’s “worn out” figure, but it runs nicely and at least I didn’t have to worry too much about it nipping up during running in!

By the way, the best price I could find at the time for an Almot piston was at Kultmopeds.de

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