I'm in the re-assembly stage of this '68 DT1 and have realized something that I should have spotted months back ( ). The 2 carb studs have been drilled off-center to the intake port by about 2 millimeters (really wish I could post up a pic as it would be much clearer). I realized this when I was looking at the red insulating spacer between the cylinder and the carb, and noticed the wear pattern on the gasket. 
Temporarily I've trimmed the gasket for a better match. 
I see my choices as one of 3:
1.) Repair the existing cylinder by having the drilled holes filled with alloy, then re-drilling and tapping for the studs, hopefully correcting the alignment issue. Basically, a machine shop expense.
2.) Obtain another cylinder that does not have this problem, boring/honing as required. This means that I may need another piston/ringset, so more parts and machine shop expense.
3.) Leave it alone and continue the re-assembly, as the bike had run this way before (it was a non-runner when I got it)

Have any members seen this problem with early cylinders? I'm wondering if I got the proverbial Friday afternoon job?

Option one, it's a valuable bike.

Keep your cylinder but source another one and start over. I believe the 68, 69 and 70..and possibly 71 DT cylinders are the same. Plenty of them out there. Find a seller who is willing to furnish the bore diameter or the piston that came out of it. Then you’ll know where it sits. Forth over (1 mm) is as much as stock Yamaha parts are available. I would stay with Yamaha parts. I bought a couple cylinders for my 68 bikes and had Bill Bune Enterprises in Minnesota fix me up with fresh bores. Highly recommended.

Cylinders from 68-71 might look and install the same... but the 68 powerband seemed "peakier" than the later models to me. I always wondered if the porting was different.

Looking at period parts books , the 69 B model has a different part  number  for the cylinder and head , than a 68 .
The 70 C and 71 E model have a different number again for cylinder and head .
I believe the 68 cylinder was unpainted , and the 69 cylinder was , but if that was the only difference ,
then I'd suspect Yamaha would have retained the 214 prefix , and just altered the suffix to 01 .
The 69 pairing went to a 233 prefix , and 70 /71 pairing , went to a 01 suffix to the 69 numbers .
The 68 head had only a single spark plug outlet , whereas the 69 had two .
Exhaust port heights were certainly different between B and C/ E models ,
but not having a 68 on hand , I can only speculate .

Was the carb flange slotted slightly as well to allow for the offset. Just carry on if it's been like it for ages & no doubt working. Or if you had a lathe could you spin up a couple of studs starting from 3/8 or 10mm steel with slight offset in a 4 jaw chuck then when machined to 8mm but having started 2mm offset--then reverse the stud & set the jaws to stud overhang spinning true then machine that bit to screw in the hole to 8mm & thread it then screw it in ending with the offset as you want it bring back to exactly straight. Man my head hurts after that lol--forget that plan & live with it as it is.

I am not sure - but hopefully someone with more knowledge will confirm the below, as this might help you find another.
The early cylinder (68?) looks slightly different. Would be interesting to know when this changed. 
Ebay item 114360614551 is an early cylinder. The fins are all full. (although this one looks ported)
Ebay item 363451903323 is the later cylinder and  has a very small cut out at the rear top fin on the exhaust side.

The non cut out ones turn up a lot less often on ebay ......but they do turn up

 

Well thanks for all the great info on the cylinders. Now I hope I haven’t screwed up. I have two 68 motors, one is on standard bore and the rest of the bike had little wear including the tanks so thinking the cylinder is original. My other 68 motor is 4th over and probably needs to go again. I bought two replacement DT cylinders and had them prepped by Bill Bune to go on my bikes. I’ll measure the port locations between the cylinders. I’m pretty sure fins on all of mine are identical but after hearing this info I’ll look a second and third time lol. The heads are obvious with the one spark plug hole at an angle. I have two original heads and two GYT one hole heads. I’m not home right now and it’ll drive me crazy until I can find my hands on those cylinders and get some measurements.

NHSteve…Don’t fret over your intake studs being off center. I just looked at mine and the right stud hole is 10mm from the intake opening and the left stud hole is 8mm from the intake opening. Doubt if multiple errors at Yamaha. Must be by design. I could only check one of my cylinders as that is all that is apart now. I’ll check the port location of my cylinders too and report back.

Tried to post a pic but not working yet.

edit…I think crisis averted for me and my prepped cylinders. Outside is identical to my 68. Ports are very close or identical. One of my prepped cylinders has both the intake and exhaust ports 2mm taller. However both ports start at same height from the top…80mm and 40mm respectively. All other port measurements the same. However on both my prepped cylinders the intake studs are centered for the opening. Maybe I should have them filled and drilled off center to match my 68 cylinder lol. I’ll have to look at the carb and see if there is a reason for the studs to be off center on the 68.

All good feedback and much appreciated. I believe it is pedalcrazy that I have been emailing back and forth with (?) and looking at our 2 intake port photos they look essentially the same. Just measuring the port-to-stud distance left vs. right I get the same values mentioned, so a 2mm misalignment.

My thought when seeing this was that in the factory for that particular manufacturing step machinery was setup to do that task, and never checked/changed maybe?

My VIN is 1717, his is 12xxx. With the '69 and later, and possible port changes, perhaps this "error" was found and corrected, as when I look at the cylinders on ebay that port appears much better centered.

As for me, for now I will continue with reassembly, as I really need to make some progress and get more of the small bits out of boxes and on the bike. I've spent a lot of time and money making the original bottom end and magneto as right as I can make them, just really disappointed in myself that I did not spot this earlier. Not as observant as I used to be.   

But option one is my preference when I can get someone to take that on. 

Thank you all for the good info! And I need to check into this imgur photo posting thing so I can get pics up.