f60 driving me mad

[monkeynuts]

hi all
iv got a 2002 f60 on which i got as a non runner (miss firing) on 759 hours.
i checked for spark, done compresion test and all cylinders were around 125-130psi.
next i went for the carbs, and after stripping the carbs down i found that carb 4 was coroded past repair, so i cleaned out the other 3 and got a whole new unit for carb 4. fitted , balanced ,serviced and every think was great for 30 hours running.
but last time i tryed to go out i primed the fuel went to start and it locked up. i popped the plugs out and found that cylinder 1,2,3 were full of fuel.
i took the carbs off and found that the was not much of a seal on the needle valves on the older carbs,so today i got some new floats and needle valves fitted them and now that operate just like the new carb.
iv now bolted the carbs back on and its running like a bag of nails, even though i have not touched any other settings
it needs full throttle to get started then once running the revs are unstable and if you rev it up it stays reving for 20seconds before it come back down.
i also noticed a leak on the top carb coming out the hole on the back of the carb near the top(facing air box) when you prime it on start up.
i tryed to balence to carbs but this just did not help. also at tick over the exhust is spiting out some fuel on the water like it running very rich.
iv took the carbs back off, but apart from checking what iv done i dont know what to try next??????????
please any help would be great as im lost and losing heart.

[99yam40]

Have you checked the fuel pumps for bad diaphragms and changed the oil? Could be full of fuel if there was that much fuel in the cylinders

[monkeynuts]

hi,
thanks for the reply, all help realy needed a the moment.
yes i changed the oil, i think i was lucky as it did not seem to have much fuel in it. so i think it some think that has changed fast.
fuel pump seems good but i have ordered a new one cos the hose tails look like thay have been glued back on
im going to strip it all down again , clean them all out and hope it sorts it out.
jus out of intrest , the mixture screew is 2 1/2 turns out. is this about right?????

[monkeynuts]

today i checked all the float measurements, the prime start movement and cleaned every think out again. but i just could not find anythink wrong. every think iv measured has been with in the tolorance in the workshop manual.
im going to bolt it back on tomorrow and start from scrach with setting up the throttle conections and dash pot, then try balence it.
but im still wondering if the is some think iv missed or if any one has had the same sort of problem.
and i cant find any setting for the mixture in the manual. any ideas??