This is been driving me nuts so hopefully someone can help me. Have a 91 CBR600F2 with a set of 33FCR's. Started out at sudco's settings of 122mains, 50slows and 1 turn out on the fuel screw. It is horribly rich, like cant stay in the garage it smells so rich bad. Went to 118's and 48's and its better, idles and revs, but still horribly rich, but idle hangs up like its still lean. Rev it and it will go up, then hang around 3500, then drop to idle around 1800. Opening the fuel screw doesnt really change much in the running and the richness gets worse. Taking a temp gun to the pipes shows 1&2 are at 400 degrees and 3&4 are at 160 and 200. No clue as to this as 1&4 run off same coil and 2&3 do, so doesnt appear to be ignition related. Valves were checked and all in spec. Compression was good and the same across all 4. Ive run fcr's on an sv so am familiar with them, but this is killing me. Any suggestions would be greatly appreciated.
Something's got to be off to have that big a spread of exhaust temps if sync is good, compression is even, valves are all in spec. Your rich smell could be those cold cylinders just throwing fuel down the exhaust?
Could it have something to do with the accelerator pump having an issue and only pumping to cylinders 3/4?
That would impact throttle response for sure, but steady state the AP isn't in play, and those exhaust temps would be much closer.
No experience with FCRs myself, but the CR specials (33) I had on the ninjette had very similar jet numbers. Are you running filters or open stacks? Those jets were pretty close on my bike with no filters. Which needles? Mine was burbly and unhappy off idle until I found the right clip position on the needles. I had yy8 needles, stock position was 4th groove, I found groove #3 was the best.
Did you completely clean all of the jets ? There are many small orifices in each jet not just the main. I use a torch tip cleaner and small gauge wire to clean each jet out. Check the slow jet and the nozzle holder GL
running velocity stacks. Yes, been thru every orifice on all of them. I put on a set of f3 carbs and its running like its supposed to now, so its got to be something in the carbs. Got a few suggestions to give a shot with, but gonna need to have it ready to ride, so going with the f3 carbs for the moment and when I have time Ill dig back into the fcr's. Thanks everybody
