Difference in engine/year/header gaskets?

[Alg]

I picked up a project Suzuki Goose that's been fitted with a 660 lump and the guy I bought it from has told me it's from an MZ and the same as that from a Yamaha XTZ660.
Looking through here, wikipedia and doing some research it seems that an XTZ660 can be anything from 1991 to 1998 and then the later bikes can be called XTZ660 also from 2008 on. I just want to know what I'm working with.
Looking on the Tenere forum it seems engine codes are:
XTZ 660 1991,92,93,94 3YF EUR(fra,esp,bel,por,dnk,gbr,nor,fin,nl)
XTZ 660N 1992,93 3YF EUR (ger)
XTZ 660H 1993 3YF EUR (fra)
XTZ 660 1991,92,93 4BW EUR (aut)
XTZ 660 1994 4MD EUR
XTZ 660 1996,97,98 4UX OTH (aus)

My engine number either (because I can't make out the second to last number) 4NN011564, 4NN011584 or 4NN011534???
Is anyone able to tell from this exactly what year engine it is? Any of those numbers don't seem to tally so is it perhaps a dedicated MZ engine? Is there an easy way to tell them apart visually? It has twin airfilters (non standard) so I'd expect it to have twin carbs and also the headers that came with it (unfitted) are a 2 into one that stays low under the right hand side of the engine so not a high level system.

Any advice on header gaskets. The ones I pulled out are copper and have a flat side and a stepped side. Which side faces out? I see there are also alloy ones also available. The decent copper ones I saw were described as 42mm where all others I see are advertised as 41. Are they all as good at sealing? Crush washers? Flat ones?
Advice appreciated.

[aah5]

Presently doing a topend rebuild on my Sport. All my parts are 3YF numbers, parts were obtained from 'Partshark' in the USA at very reasonable prices. The 4NN numbers are the MZ engine No. not Yamaha.

[Bill Jurgenson]

Re head gaskets:
there is no difference for all 660 engines in the size and position of the various holes.
What sort of gasket one prefers is personal preference.
I would definitely go for either an OEM or a Cometic gasket.
Copper gaskets are not for the casual user. Beware that they have there own set of problems (and advantages).
Altho I use them myself for some applications, I definitely do not recommend them for the hobbyist.
I also use aluminum gaskets which I make myself, e.g. for the cylinder foot when I need a different thickness.
I get the copper gaskets from http://www.coppergaskets.us

[Skorpion]

Hi Alg.

Taking a look at my 1998 MZ Skorpion engine number I find it is 4NN02, so I take it that your engine is before 1998,
And your exhaust is also from a Skorpion.

Yamaha's engine code for this engine is 3YF, engine parts can be ordered from Yamaha or MZ, Grahams Motorcycles are the world wide MZ parts supplier.

http://www.grahamsmotorcycles.com/index.htm

I hope this helps.

[Alg]

Thanks all so far.
So it's an MZ engine and likely from a Skorpion, thanks for the Grahams motorcycles link.
I might not have made myself clear when talking about gaskets but I was talking about the exhaust header gaskets.
Should I buy copper or alloy and which way round do they fit. Flat or stepped side facing out?

Thanks again.

[Skorpion]

Sorry can't help on gasket type.
Just ring Grahams they are very helpful and genuine ones can't be that expensive ?.