1973 RT3 360cc 4th over 1.00mm Piston & Rings Wanted - Australia.
Yes I know there's a couple on eBay for blood money but was hoping someone mite have something here not so expensive.

Cheers Lee

Welcome from NZ. Yeah i just went looking for an hour for ya but not looking good is it.
Tried all options of 360 DT & YZ etc & as most if not all models should work.
Even piston port RT1 with holes drilled which is a bit dodgy as skirt isn't reinforced like the correct model with holes.
I've used a YZ400 2X5 82mm kit from "79, one year only long stroke 82mm with about 5mm off the skirt base & head modifies a whisker to fit over the 82mm bore. But, can't find any of those either.
I wonder if we're limited to how deep we can search from down here on fleabay as used to be lots out there once upon a time. & as you say, the cost is just criminal.
Mind you our dollar is useless nowdays.

I actually just took a punt on an "unknown 81mm piston" on ebay US that does visually look correct and says 1.00 on top, see if I get lucky otherwise RT1 pistons seem reasonable in 1.00mm over but as read in a previous post the rings are different heights and sounds like a headache, screwed either way really, spend the same amount trying to resleeve it if you can get a sleeve

Yeah I even use a VPN and search ebay US etc, about 3x available all for blood money :(, cheers for looking

I would like to add my experience with oversize pistons. I have three RT3 regular riders. Two of them had third oversize pistons when I bought them. After awhile one of them went into a high over rev lean condition caused by separation of the cylinder liner and causing an air leak between the liner and jug near the base. Air found a way to get in. On the other I was having trouble jetting the carb, found a separation in the same place. The cylinder liner on the 250 starts out at 5mm thick. The 360 is 4mm. When you get to the third and fourth oversize the liner is very thin plus the 360 generates more heat. The shop that does my cylinder boring recommended not going past the second oversize on the 360. They said going to the fourth oversize on the 250 is OK.

I have 2 NOS cylinders with standard, first and second oversize pistons and rings. Send me a PM if you don't find a solution. I'm in the US near Washington DC.

If the kitchen is too hot for you

chances are the outside temperature is comparable

and being stuck in a freezer with no oxygen

is not a move into freedom.

pay or quit mate!

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Persnaly i've had no problems going to 4th over but interesting to hear of that. In fact a mate pressurised a problem RT1 piston port motor & said it was oozing out everywhere around the cylinder. Maybe i've just been lucky.
I've gone out to 'techicaly 8th over' [out to 82mm with a 2x5 kit] & that ones still out there winning races in vintage--just not with me on it lol.