I have two 2007 Honda BF50's that I bought a year ago to convert my hurricane 530 back to twin engines (from a single 75 4s merc). Engines are carbureted 3 cyl remote control type. The previous owner ran the engines for me before I bought them and they ran pretty well. Both engines were in remarkable physical condition, bought as a pair(sequential serial numbers), fresh water use only and no sign of use at all really aside from some heavy sand abrasion on skegs/propellers(sandy river use). from the props up they look like they just rolled off the show room floor.
Before mounting the engines, I wanted to do a full service on them and make sure they were in good running order while they are still on the stands.
Trouble set in on the first engine I started.
I bought a new fuel tank, hose and fittings, put a new in-line fuel filter in the engine, and filled the tank with fresh fuel. connected a brand new set of controls. When I turned the key the engine started instantly but it ran like crap, bouncing around on the stand. Pulling the plug wires one at a time revealed that it was firing on the top cylinder only (pulling top wire shut the engine off, pulling wires 2/3 had no effect).
Next I opened the drain screw on the carb bowls, lots of clean fuel present in all 3 bowls, no dirt or debris visible.
I then pulled each spark plug one at a time, grounded it against the block and turned the engine over with fuel disconnected. Good spark on all three plugs, plugs dry, no sign of excess fuel in the cylinders 2/3.
Decided to run a compression test at this point just for piece of mind. 185psi on all 3 cylinders for a luke warm engine block. Just about perfect, major relief!!!
Re-installed the plugs, reconnected fuel line, primed the bulb and started the engine again. Engine now ran perfectly smooth on all 3 cylinders for about 2 minutes!!! I goosed the throttle a few times and raised the rpm for about 30 seconds. When RPM's settled to idle speed it started running like crap again
Pulled the plug wires one at a time again and found only firing on cylinders 1 & 2 this time. No sign of life from cyl 3. Shut engine off and restarted, only running on cyl 1 again now.
Drained all three carb bowls again, lots of fuel in all bowls.
So what should I do now ribnet experts? Tear the carbs apart and give them a cleaning? Ordered new gaskets today just in case. Seems like I might have intermittent clogging of jets on cyl 2 & 3 carbs? I don't think the floats are sticking because the bowls are always full of fuel. I started this project later then I wanted, did not mean to let fuel sit in carbs for a year but life gets in the way. Previous owner said fuel was stabilized but who knows.