Newbie from the UK with an ETZ 250/301 and a few questions

[muddy]

Hello guys (and girls?)

I'm Matt, a newbie to the forum and MZs, but not bikes. I recently acquired a 1985 ETZ 250 (at least that's what it's registered as), it hasn't run for 14 years, and I plan to get it back on the road and use it as my daily ride. It's in pretty poor cosmetic condition, but from what I've looked at so far it's mechanically sound, and overall not as bad as I thought So far all I've really done is strip everything down and give it a bit of a clean, but I must say it's great working on such a simple bike, usually I work on modern BMWs, so it's makes a change fiddling with carbs and points instead of electronic fuel injection and diagnostic computers

I dropped the engine out yesterday and took the head and barrel off, and this is the first question, the piston measures approximately 75mm across, and my friend thinks this is actually a 301 engine as the 250 piston is smaller (about 69mm?), is this correct?

Next question, what carb should this engine have? Currently it has a 20N2 I think (I forgot to note it down so I'm going from memory here), is that the correct carb if it is a 301 engine instead of a 250?

Final question, anyone know the tyres sizes for a 250? I'm away from home at the moment and would like to order some for it, but I don't know the sizes and can't check what's currently on the bike.

Thanks in advance, Matt.

[djsbriscoe]

Hi,
The carb is a BVF 30N2 for the ETZ251 and ETZ301. The jetting of the carb differs for the ETZ301. Later models use Bing carbs.
I'm not sure about the piston diameter as I dont have the manual to hand.

David.

[manumensa]

Hello and wellcome
The girls gone because iceman post a lot of pin-up pictures.

75mm. piston are for 300 cc.

Front wheel: 2.75x18 (I think a 3.00 is better for the big brake power)
Rear wheel: 3.50x18

All info in http://www.miraculis.de

Saludos/Regards,
Manuel

[Spitfiregoggles]

Hi Matt,
the factory manual states stroke/bore of 65/69mm for the ETZ 251, so it sounds like you may well have a 301 engine. The factory manual I have doesn't cover the 301 and Haynes states bore for the 301 as 75.5mm so I reckon this is almost certainly the case.
Wheel rim sizes Front 1.60x18 Rear 2.15x18 (250 and 300 models), 2.15x16 (251 models)...acc to Haynes
Tyre sizes for ETZ251 (F) 2.75 x18R (R) 3.25 x 16R......acc to factory Manual.
Will check this on my bike when it's daylight!
Sounds like you had best check what rear wheel your bike is to be honest as I suspect they are interchangeable between 250 and 251!
Hope this helps, have fun; I am enjoying my ETZ251 immensely!
Simon

[DAVID THOMPSON]

check your rim sizes i have found an odd mix of rim sizes on some of the mz bikes
it may not be what the book says

fellow had a saxon tour just like mine but it had a 18 inch rear wheel mine is 16 ???
dave