Questions from a two-stroke virgin.

[oilyrag]

Hello to all,
Greetings from a new member of this forum, I'm hoping to benefit from some of its wisdom and experience, and possibly help others in time.
I'm rebuilding a 1973 ES250/2 which I was given, and which I took on because it was me or the crusher. I've had quite a few old bikes over the last 30 years, mostly Nortons, Velocettes, BSAs, and Earles Fork BMWs, but never an MZ, or any other Two-Stroke for that matter.
It was last taxed in 1986 and seems to have been left outside in the wet climate of Lancashire since then, the engine was in bits in a washing up bowl, and the cycle looked like this, although the picture is actually a bit kind to it, but it gives an idea of the state of things:-



I'm well on with the rebuild now but I need a little help with one or two questions which have arisen:-
Why are there different thicknesses of head gasket available, and how do you determine which to use? The Haynes manual just says to use a new gasket, and the Zschopau one that the joint is face to face so neither help at all. I know that the Gasket thickness on the Gold Star had to be matched to the individual combustion chamber, but that was a racing engine, after all. What is the purpose of the stepped face on the joint? (just curiosity that one).
Headstock: should there be a dust cover over the upper headrace or not? The parts book shows two discs as part of the steering damper, should they be fitted on non damper bikes, and when the damper wasn't fitted, what went in the hole in the handlebar cover?
What do the various key positions do, as its going to be difficult wiring it if I don't know?
Thanks a lot for any help you can give me, as it would save me a lot of trouble with these questions, and, no doubt, a few more before this MZ is back on the road,
Cheers!

[djsbriscoe]

Hi,
The different thicknesses of gasket allow the squish clearance to be changed. Just google squish clearance for an explanation.
I can't help you with your other questions.
If you join this yahoo group

http://groups.yahoo.com/group/mz_riders ... =330951138

They should also be helpful.

David.

[oilyrag]

Hi all,
if anyones interested, here's how it turned out, I'm now running her in, and will, in due course, be asking a few questions, but for now:-













Sorry, don't know why my top two pics are cropped, just imagine the rest.

[DAVID THOMPSON]

outrageously NICE JOB is all i can say
if your day job goes away consider being a bike restorer
Dave

and do lock it up so some one don't NICK it on you

[stogadog]

that is well nice - Ive only just read your post so it's pointless answering your questions - you know the answers! Good to know there's another Trophy oiling the Lancashire roads! What do you think now you have got it done then? Enjoying the massive gap between third and fourth?!

[oilyrag]

Hi all,
yes I noticed the gap, in a family sort of way its like the gap between 2nd and top on a 3 speed Bantam my cousin had, the feel of the gearbox is more like a plunger BMW than anything else I could name, certainly not like a Velo or Norton. Mileage wise its too soon to rev it much, but what sort of cruising speed should I expect, once run in?
Setting the tickover is fiddly but once rolling the handling and comfort are great, the lights are VERY good for 6V and the brakes not as poor as I was lead to believe, when properly set up, anyway.
Struggling to get a good seal between pipe and barrel, anything going thats better than the standard crush washer?
Also am I correct in my observation that the odometer on the MPH speedo racks up in km, the miles seem to come around too quick, and the markings on the back of it and a km clock I have are identical?

[cat]

WELL DONE! WOW!

When i saw the first pic - the unrestored state - i was going to say "Good for you" for saving it. Then i saw the pics of it restored. oh my goodness, i wish i was there so i could try to buy it from you.

[DAVID THOMPSON]

this is too nice not to show full screen saver quality pictures
dave
its a bit strange looking but nice
CLICK ON PICTURE 2 TIMES FOR A BIG VIEW site crops picture size

[stogadog]

Yes - the exhaust doesn't seal very well does it? I have put a bead of silicon sealant on the threaded ring on mine and it has stopped it to an extent but it still leaks a bit. I wonder if it's just "one of those things" - what with having a moving rubber mounted engine connected to solidly mounted exhaust. My bike will cruise at about 65 on long straight stretches but it does take ages to get there from 55 or so, so on normal (bendy!) roads I don't really go above that. It is nearly 40 years old so I don't mind travelling slowly! I'm intrigued that you have good lights - mine are rubbish. What bulb have you got in? I ahve never seen another Trophies lights so I just thought 6v lights, therefore a bit crap. Wonder if I'm losing Volts somewhere to the lights?

[Dzundzun]

What a cracking job you've made of it! I have the same model and colour scheme about to be rebuilt so I may pester you for tips.

[radiograf]

[quote="! I'm intrigued that you have good lights - mine are rubbish. What bulb have you got in? I ahve never seen another Trophies lights so I just thought 6v lights, therefore a bit crap. Wonder if I'm losing Volts somewhere to the lights?[/quote]
Check all your connections are clean and not corroded, especially the earth, as 6v systems have a greater loss due to resistence than 12v( something to do with ohms law if I remember my 40 yar old physics lessons correctly!). Also check on ebay, as 6v p4t halogen bulbs are available, assuming that the ES250 takes this bulb, and not the Bosch Ba20 type.