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In my quest fora standard Italian cylinder, I have acquired two Italian 200 cylinders, one of them has a mark by the inlet port, any idea on what model it is from, the other has no mark but a shallow exhaust port same again, when I clean them up I will take some measurents, but if anyone has any ideas in the meantime it would be nice,

Does either barrel have a number stub (with number) off the side of the inlet manifold area (factory fitted Italian barrels will have)?

The barrel on the left of the photo does not seem to have a stub here but does have something that I can't make out. This is where most manufacturers will follow Innocenti's lead and place their mark of identification; SIL barrels commonly have the SIL 'S' in circle logo, one of the common aftermarket Italian barrels has an M in a circle, etc.

I can't see the manifold area on the barrel to the right of the photo because of barrel position. What does this show?

Once you identify make, we can then move on to spec... i.e. the top fin notch that is evident on the barrel to the left.

Adam

As you have seen already this is an SX200 barrell.

^... Or could be a GP200 barrel as they both have the notches out of top fin but without the spigot cross cut that the SX and GP150 barrels have. The signs are the same for the SX and GP 200 barrels but the porting differs slightly.

That is a very good and clear photo of the number stub that I was going on about... ta.

Adam

Given that when I acquired it Adam you could still buy a new Italian GP from a dealerI would bet this month's pension that it is an SX barrel.

Port maps if these are any help for the two barrels

Added dimensions, looking for a barrel with low down power,not looking for extra power just a good standard bottom end

If I had to bet,
top one SX,
bottom GP or tuned.

As mentioned previously, the identification markings on Innocenti factory fitted SX200 and GP200 barrels are exactly the same so I've got no doubt that Digger is right in suggesting that his may be an SX200 barrel. Basically, they are the same, to the point that they have the same Innocenti part number. If you wanted a replacement from original stock, they would have sent you the same item as a replacement for either the SX or GP 200.

My thoughts:

1. The measurements given for the top tracing are bang on what I have listed for my original SX/GP200 barrel with #1 stub number. I really do mean mm perfect! I cannot state for certain that mine is SX or GP as I took it off a motor that I don't know the history of. My #1 is still on a 66mm bore.

2. I have a second #1 barrel which varies slightly but as it is on a 67mm oversize, the very minor (very minor) differences are probably just a result of the ports being cast at an angle, meaning that the bore face measurements change slightly when the cylinder is bore out.

Neither of the above barrels have any work to the ports, as identified by the casting marks being untouched in the ports (not even polished.

3. I then have another barrel that is still on the 66mm bore and, likewise, has no work to the ports. However, this barrel has an exhaust port that is 21.25mm tall, with 38.25mm to top of bore lip. This is a #3 stub SX/GP barrel.

4. In my 'little black book' I have a tracing that I took from a Jet 200 original barrel on 66mm bore and this has both the inlet and exhaust port at 18mm tall.

5. The original number stub TV200 barrels that I have are quite different again and fall into 2 camps; early ring breaker and later non-ring breaker. Both are untouched port-wise but it is worth noting that my later narrow exhaust port TV200 barrel is a number 1, whereas the earlier wide port ring-breaker is a number 3, which supports the statements of others that the stub numbers probably do not represent a chronological / linear development/revision process but probably have a manufacturing significance (e.g. cast number, production line number, batch, other?).

In consideration of the above, and knowing that the higher revving GP200, with 22mm carb, higher revving non-baffle standard pipe, reduced ignition timing and lower ratio gearbox, would have benefited from the slightly longer exhaust duration of the porting illustrated by point 3 above. The lower revving SX200 on longer gearing would have pulled better at low revs on the porting of the barrel in point 1 above. If I were a betting man then I'd suggest point 1 is SX200, point 3 is GP200, noting that the Jet barrel in point 4 is very similar that shown in point 1 (Jet200 and S200 being pretty much the same spec machine).

I reckon that Dimitrios is probably right in thinking that the top tracing is of a standard SX200 spec barrel and the other is a very slightly tuned barrel, of the era when raising the exhaust port by 2mm was a standard porting modification. Please note that we've not yet confirmed that either of the barrels are factory fitted and they may well be aftermarket, of which there are many versions, representing all of the TV/SX/GP specs and beyond.

Adam

Note to self: I must get out more!

I' agree with everything Adam says

^... I flippin' wish my wife and kids would

Thanks for the info Adam I will pop over to Oxford when you next meet, Tuesdays ? will bring the barrels.

Cool, it will be good to see you.

Yep, Tuesdays, earliest there at 8:00 then the rest in dribs and drabs.

Adam

I have an SX cylinder that came off a Danish import a few years ago, it has the same measurements as pic 1 with 2 notches in top fin but I can't make out the number on the inlet stub. I've no reason to doubt it was an original cylinder.

If it has a number stub then it was probably just a casting issue as most aftermarket barrels don't even have a stub!

Do the numbers mean anything?

from previous...

5. The original number stub TV200 barrels that I have are quite different again and fall into 2 camps; early ring breaker and later non-ring breaker. Both are untouched port-wise but it is worth noting that my later narrow exhaust port TV200 barrel is a number 1, whereas the earlier wide port ring-breaker is a number 3, which supports the statements of others that the stub numbers probably do not represent a chronological / linear development/revision process but probably have a manufacturing significance (e.g. cast number, production line number, batch, other?).



Digger, that doesn't provide you with an answer but is food for thought.

Cheers

Adam

Thanks Adam

You are very welcome, for what little use it was. This is a question that I'd like answered too. How knows... that is the question

Adam

Mike,

If you have a copy of it (if not, why not?!) go and have a look at the standard SX200 port measurements quoted in the 60's tuning manual, which I understand is available in PDF off the web somewhere.

Season's greetings.

Adam