Fresh restoration, no miles ridden while waiting on registration processing.
My T500 has been flooding and after much tinkering the problem came down to an unexpected source. Started on the right pot would stop firing and then blowing fuel at the header joint. Pulled the carbs some dirt in the bowl, so cleaned both carbs, pulled the tank flushed again, acid cleaned, flushed a few more times for good measure. Checked the float heights put it all back.
Ran for a bit now stopped on the left, raw fuel. then stopped on the right raw fuel. About 1/4 pint drained from both crankcases
Pulled carbs, bowl's clean no crud, so swapped out the float valve seat and needles from after market to new mikuni. Set everything up and reinstalled. Same result flooded both pots.
Pulled the carbs again, jury rigged a fuel supply to test on the bench, fuel spurted out of every orifice. Took the float bowl off to see if the valve would stop the fuel flowing. Very light pressure on the float valve was shut tight no fuel getting through. Float checked, no damage, no fuel in side, moves freely.
Put the float bowl back on without changing anything and it floods!
To cut to it, when I refurbed the carbs I bought new brass but made my own gaskets from gasket paper. Paper I used on the float bowl was ~3x thicker than the stock gasket. Turns out the arc of the float on its pivot runs so close to the walls of the float bowl, dropping it about a millimetre caused it to touch and prevent it closing the valve. I can't figure out where it touched, you'd have through the draft angle on the casting would move the wall away as the bowl drops? Assembled with no gasket doesn't flood, put the gasket back it does, played this game a few times just to convince myself it was true.
Being a bit spooked with it being so marginal, I shaved a little material off the inner bowl walls in the mill to create more clearance, plus I didn't have to wait for and order OEM gaskets. Now when you tip the carb you can hear the float move inside. Everything back on the bike and so far so good.
Sharing this a cautionary tale for anyone installing non OEM spec gaskets or thinking of doubling up OEM. Thickness seems critical, you might be lucky and the bowl sits in place where is misses. This seem to be the case on my LH carb sometimes it would go together OK, next time not and it would flood.
Got my registration through today too, first proper ride this weekend.
