oldrodder, did it go well before with the 34mm carby on it or only since you put it on? if the latter, easy to guess that unless something like float bowl too high/low or one or all of the jets too big/small, that the machine just don't function properly with the bigger carby on it. i guess you won't know until you change a few jets and see it improves performance. so might have to buy yourself a few main jets, pilot jets, needles maybe and experiment. as for float height, i reckon set to similar height for the 32mm carb. take float bowl off, turn upside down, and measure (usually) from top edge of the carby body to the tang (that right guys? can't remember myself....). or just go back to the 32mm, and give her a bigger main jet for the dg pipe? its often said that a bigger carby can just reduce performance, due to less air speed thru the bigger venturi chamber and into the cylinder. less airspeed, less charge goes in.
