Nathan, my information, not all presented here, says the 1984 RC500 carburettor was the unit used on the 1985 CR250.
They may have been available to Honda in 1983.
The CR250 carbs were available, retail, over the counter in 1984. I'm not allowing for hair splitting over the various calibration parts but it is the same die cast carby body.
This means a savvy privateer, perhaps racing out of a Honda dealership, could have fitted a carby identical to the RC500 unit in 1984.
1. Was the carb you could buy in 1984 a 1985 model part?
2. If so, do you not think it's odd that it has escaped the attention entire OzVMX brains trust? Blokes like JohnnyO, KTM47 and Middo have been around the sport for a long time, with much more than just a passing interest.
3. If you are withholding information, then why are you continuing to debate this? Either shut up and put your submission in to MA, or lay it all out here. Claiming that you have more info without disclosing it, makes it sound like you're bluffing.
If you want to win the argument on OzVMX to gain support, then you wouldn't be playing secret squirrel.
If you don't care about winning the argument on OzVMX, then you will simply put your submission in.
4. It's not impossible, but I find the idea of a mid-80s works 500 having a 38mm carb to be unlikely.
Plus everything Evo550 just said.