Is this a 69 DT1 cylinder?  


 

Quite possibly . The top three fins have been trimmed , presumably to accommodate an expansion chamber , possibly a GYT pipe .
I think I saw this on Ebay . If it came with a brown / red insulator block on the intake side , it will be a 69 , though it might have been ported .

Appreciate you looking this over. The pic I posted is not that particular ebay cylinder, though they do look alike.

I was having some problems w/engine performance and wondering if maybe the cylinder on the engine could be an issue after noticing the 2nd cylinder looked slightly different (the one above). Both came with the bike when I bought it. The one on the bike shown below.

pics of cylinder/head currently on engine:

Everything looks fine from what I can see . Could you post a photo showing the view from the left side .

DT1MX were black i think in 1970 but porting would be a giveaway if you compared with original.
Might've been black with a shiny edge on the fins. But hey it's only paint so who knows.
Did they have an id part number or a reference on the base apart from 246cc or something.
Looks like a hacksaw scratch on the next fin down so yes might be standard but been cut off for the expansion pipe.

That is a DT1 enduro cylinder with the top three fins cut by hand to allow clearance for a GYT pipe.  This is a factory GYT/MX cylinder.

imgur.com/a/2fnoIo2
 

A gyt kit cylinder was chrome & unpainted. A dt1mx cylinder had a cast liner, was black & was boreable. In fact I have one on a motor but it's to buried under other stuff to easily check. Have a 360 crank in that motor--just saying. If you find the porting specs & measure to the top of the exhaust port & transfers that would tell you enough. If by chance you're running an mx cylinder with a standard compression enduro head it'd be quite flat in power with less down low than standard & lots of revs but little torque in those revs. Inlet where the spacer fits up would be 30 or 32mm by memory on the Go Fast cylinders. All a lifetime ago.

Yes, GYT and MX cylinders were not always the same.

That is correct that the early GYT cylinders (68/69) had a chrome bore and the later (70/71) cylinders had a steel sleeve. I was commenting on the profile of the fins on the cylinder posted in this thread being a cut enduro cylinder. The cylinder I posted shows the profile of the fins on all of the GYT/MX cylinders regardless of year. As the porting is different on the GYT/MX cylinder an enduro cylinder with cut fins will not provide the performance gains of the GYT cylinder with the additional GYT parts (head, carburetor and pipe).

What RT325 was saying is for some years/models there were 3 versions of cylinder.  

1. The Enduro
2. The MX
3. The GYT 

If you bought a factory "MX" model, it had an iron bore.  The GYT cylinder had a chrome bore and was sold as an alternative "racing" part for both the Enduro and the MX.

GYT and MX both would have had the fins cut.