2 Strokes Down Under

I think I have finally sorted my carbs out on the 500, but I've still got an issue.
It runs pretty crap after a while. When I first get it going, it goes like stink, but starts to play up. Almost like cylinders start to give up.
I let the bike cool down and it's good as gold again... for a while.
I don't think it's running out of fuel, because it doesn't recover after letting it idle.

I'm going to change the radiator cap - it's currently a 1.3 and I think it should be a 1.1 so I thought maybe the head gaskets are leaking due to excess pressure instead of the water expanding into the expansion tank.

I used Vesra head gaskets too I think, which may have been a mistake.

I'm also going to change all the plugs since I had carb issues and I know at least one was fouled (which is now changed).

Anyone got any other ideas?

I hate these now-you-see-me-now-you-don't bullshit problems. Coil on the way out? Perhaps hit them with some spray freeze when it is playing up and see what happens?

I don't have easy access to the coils to be able to do that unfortunately.
But yeah, it's a bitch to sort those kind of issues.

Sounds like its ripe for the selling .

Runs perfectly at the sale and when the punter returns; 'gee mate, it never did that for me. What have you done to it?'

(Sorry, I haven't anything constructive to add )

OK, it's not for sale any more

Turns out I had a couple of issues I think. Firstly there was crap under the needles in two of the carbs.
Cleaned them out and fitted a couple of filters.

I also have a feeling that one of the chokes may have been sticking on.

So that part is sorted and the bike is running great. I just have an idle issue I need to sort out now. I'm seriously considering buying brand new carbs so I don't have to faff about with these old ones.