I dbout it , sounds like a hydro lock when flooded sending the piton back the opposite way , the only place the pressure can escape is out through the carb..

I could be wrong..

Ok heres another theory , Do you have an MSN on any of these carbs ? if so feel how loose it is .. if its not tight as a squirrels nuts then you will have tune probs. Take out the MSN and cover the end seal with plummers tape, make sure you only cover the very end of the seal, screw this back in and see what happens..

the problem you are encountering in my opinion is tuning the engine from a full tank. If you were to tune the engine from half to 3/4 empty you would have a better average tune. remember the tuning on these things changes as the tank pressure changes. When you are at half tank you have an average pressure. When you tune from a full tank you have plenty of fuel pressure, forcing fuel into the carb, you lean it to suit, but when the pressure drops you have less fuel = lean engine. this can over heat it to the point where the power dropps off out of corners when the lsn is too lean or it wont go hard till you hit half way down the straight, meaning too lean on HSN.. When this is left for too long you will pre maturely wear the piston on the exhaust side and cause blow by .. then all sorts of other problems occour.. and tuning isnt gonna fix it .. When its cold it will seem like its got heaps of pop , but at temp the flat spot on the piston will allow compression to escape and stoppig the pupm effect of the engine. This leans it out even further cos thers no suction to draw the correct amount of fuel on the down stroke ..

So best way to fix this is to tune it right from the start , if once you got the tune right and one day its all out .. dont try to fix it with tuning , look around the engine for a cause or strip down the engine to see why its changed.. Unless you have a crappy carb with loose needles you should only ever have to make very tiny changes to tuning if any .. I tend to get a tune on an engine then leave it .. dont be tempted to lean it off when you start it cos it seems rich... it takes half a tank to get to operating temp..



Hope this helps !

Cheers mM