ETZ250 piston in 1976 TS250? + related questions

[polycyclic]

Hello fellow smokers, I have been offered a new 69mm piston for an ETZ 250 and would like to know if it would fit my 1976 TS250. Also, how would I find out if my engine had been rebored?...
A little more background - I bought this bike "for next to nothing", but the engine and clutch were seized, apparently from standing in a backyard for 4 years or more.... Yesterday I sprayed some WD40 through the plug hole and left it for a few hours; later I put the machine in gear, sat on it and rocked it back and forwards - after a couple of minutes of acting like an eight year old (minus the "vroom, Vroom!..." vocal accompaniments, of course), low and behold! the engine broke free, followed by the clutch a few moments later - phew! I was beginning to think the seller had been less than honest with me when he extracted £15 of my hard-earned cash from me for his old MZ....
Anyway, the engine now turned freely on the kickstart, so I did a compression test which gave about 150 psi after 3 kicks - seems good to me. The question is, shall I go to the next stage and prepare the engine for starting, of should I take the head off and inspect the piston, rings and bore?
Next question... Where would I get a top end gasket set for this bike in the UK? I can't seem to locate one through internet searches... Although there is a breaker offering USED gaskets on ebay for £7 a go described as ".2 or .4" - excuse my ignorance but I assumed that once used, a head gasket would have had the life flattened out of it and would be of no further use - further to this, would I use a ".2" or a ".4" and why?
On a non-engine matter, I've noticed a small steel rod that hinges out from the left side frame near the front of the seat - it is about 4" or 5" long and 1/2" diameter - at first I said to myself, "...a fold-down pillion hand grip! - it's lost it's rubber..." (last time I said that my girlfriend slapped my face)
"...How ingeneous those East Germans are!..." (having owned a Lada as a student (cheapskate? - who me?) nothing would surprise me), but then it dawned on me that there wasn't one on the right side of the frame, so unless this was a modification for a left-handed (perhaps that should be left-winged?) East German amputee, then it was for something else... Any ideas? A sawn-off vestige of a sidecar mount?
That's it folks! Thoughts or suggestions welcome!
My Name is Ken and I'm a Bikeholic.

[djsbriscoe]

Hi,
Have you tried Burwins in London?

http://www.mzspares.com/index.html

They are the experts on MZ 2 stroke engines and should be able to get hold of a Gasket set for you.

David

[Eric Frith]

The head gaskets arrive in different thicknesses to allow for the adjustment of the "squish",

If the bike had a standing seizure then the head and barrel would need to be removed in 80% of cases, but more often than not all parts are salvagable.

Eric