I am pretty sure this has the original chrome lined cylinder, but I won't be positive until I get the engine apart.  The engine seems stuck right now.  I've been soaking the cylinder/piston with Kroil.  When I look in the exhaust port, I can see the piston has a lot of scratches.

 

 Any ideas what different cylinders would fit on this bottom end if I can't get the cylinder replated or fixed?

Does anyone have any suggestions for finding a DT1MX air box?  I know this has the 285 prefix for the part number, and looks different from the DT1 enduro.

Thanks in advance to all the DT1 experts!

I'll stick my neck out & say--my only recollection of the chrome bore was as a genuine gyt kit cylinder for the dt1. I fitted one on the bosses bike [complete kit head cylinder piston kit & 30mm carb plus chamber exhaust] & was great excitement. Bike was december "68 so kit would've been 'then' as i fitted it & he headed off to Nelson NZ for the international meeting [i'll find a pic of that]. Remember that time well. Better check dated of that meeting though incase bike was a year old by then.

Just now saw this bike,
She's a Peach !!!

I'd just like to correct my earlier post . On checking my parts books RT 325 was correct
in saying both the DT1 M and DT1 MX came with reborable cylinders with iron liners .
It was only the GYT kit cylinder that had the Chrome plated bore .
My bad .

Thanks SWOOP56. I'm sure not always right haha. The MotoCross i reffered to in Nelson oposite the camp ground by memory, hilly & stoney [& wet & no fun lol] was on 29/12/68 so i'd just fitted the race kit & boss headed down south & looks like he lead the big class for a while on the DT against 380CZ's & Husky 360's & ended up in 3rd place all day. Also against 500 Matchy Metisses & the like. I was there on my Mettise but had a terrible day in the mud. Think i loaned my B33 bsa [on methanol probably] to a mate & he thrashed me all day haha.

Thanks for the responses!  Looking in to the service manual LIT-1162-14-99 on page 67, it shows the GYT cylinder (alloy?) as part number 214-11311-70 and the part list for the '70 DT1CM shows the cylinder (sleeved?) as part number 285-11311-00.  I guess that makes it simpler to get work done on the cylinder!

The piston says 62 K with an arrow pointing toward the exhaust and 950 on the intake side.  Do you all think this an original non oversize piston, or something else?

 

Edit:  I just measured the bore at about 2.755 inches or 70.0 mm halfway between the piston and the top of the bore.

The piston markings tally with Std. size OEM piston .

Here’s the GYT Kit conversion page from my ‘68 Service Manual

 

50 years & still on original bore. Blimey. Built them tough in those days.

Jgersh wrote: " Here’s the GYT Kit conversion page from my ‘68 Service Manual"

I wish the GYT kits were still available.  I could use most of the parts!