Topic: 75 550K carb issue has me stumped

[carefree]

So I've got my 550 carbs driving me crazy. Ive got the number one carb leaking out of overflow only occasionally. I can ride it around my neighborhood for 20- 30 minutes and it runs perfect with no leak, park it letting it idle for 5 min or so and no leak, start it next day and it leaks within 2 or 3 minutes while warming up then stops and starts leaking at will. I rode it out to a wilderness area about 12 miles from home and it ran perfect until about halfway back where it felt like it was running with the choke is on and barely made it home. Next morning start it and it runs great again. WTH Ive cleaned carb multiple times, have inline filter, have checked float level,cleaned and polished valve seat and checked float for leaks, checked overflow tube for cracks or leaks and have come up with nothing. Nothin obvious to me so looking for any suggestions. Thanks Jim

[BenelliSEI]

Jim..... on the carb that occasionally sticks and overflows: ensure one of the floats is not splayed out and ever so slightly touching the wall on the float bowl? That bit of drag can cause those annoying inconsistencies.

On the rough/clean running: using NGK plugs? Install a new set.rough running when hot could also be a bad condenser?

[HondaMan]

Jim..... on the carb that occasionally sticks and overflows: ensure one of the floats is not splayed out and ever so slightly touching the wall on the float bowl? That bit of drag can cause those annoying inconsistencies.

On the rough/clean running: using NGK plugs? Install a new set.rough running when hot could also be a bad condenser?

Also, re: running badly when warmed up - the normal failure mode for the coils, which do have a limited lifetime, makes them act like this. When the coil gets hot, the flaking-off enamel wire insulation lets the wires inside touch each other, shorting the coil internally while hot. When cooled off an hour or more, they work again for a while. These wires were insulated using a 10-year enamel coating. Many of them, particularly in the 500/550, are dying nowadays just from their lifetime being over.

Does the bike have points & condensors, or has someone installed an electronic device like Tytronics or Dyna S? This will bring up an entirely different topic, involving the bike's small alternator...

[Kevnz]

Had the same issue, riding along fine and then bike started running rough. Looked down and fuel was pissing down over the sprocket cover; no1 carb flooding. Rode to my destination by turning the fuel tap on and off. Left the bike at the destination, where it was being inspected, picked it up a couple of days later and the problem has not yet reappeared. Original brass with needles and seats polished. Frustrating.

[Deltarider]

In addition to Benelli's good advice, here some more tips.
To cure intermittent leaking, please read the steps in: http://forums.sohc4.net/index.php/topic,183637.msg2125986.html#msg2125986
In general: http://forums.sohc4.net/index.php/topic,164089.msg2158019.html#msg2158019
In over 41 years I had best results with leaving carbs in a natural state, which is wet, when hibernating. Just drain the carbs say every 2 months and let them refill. By all means: stick to OEM brassware! Mine still doesn't show wear after over 138.000 kms. In all those years I only had to replace the bowl seals and the little O-rings around the main jets.
When you suspect the condenser(s), aka capacitors, this vid may help:
 

At the breakerpoints a tiny bit of sparking is normal, excessive sparking or arcing is not good and can indicate a bad condenser. So in this vid the left condensor (1+4) is bad, right condensor (2+3) is good.
Unlike the Dyna, the Tytronics EI is NOT known to cause more current. With a duty cycle limited to 50%, draw is, in theory, even less than the stock ignition, which sees a duty cycle of over 50%. The consumption of an EI itself is usually futile.

[newday777]

How is the inside of the gas tank? Rusty at all?
Do you park it on the side stand?

[carefree]

Thanks for all the great ideas, gas tank is really clean and running an inline filter and new petcock. I've kinda thought I need to test the coils but the leaking didn't make sense (at least to me). I'll for sure test them now. The floats maybe hanging up inside the float bowl is a definite possibility and really the only thing that makes sense. Ive taken the float bowl off and turned on the gas, fuel flows as it should and shuts off completely when I lift up the float, no drips whatsoever. Ive tested the overflow tube by hooking a hose to the bottom while off bike, filled with water and blown air into hose while holding other end to look for obvious leaks, again nothing.

[carefree]

So finally got this squared away with the advise of a friend who has the same issue with a 80's Goldwing he was working on. I assumed each carb was an individual system for each individual cylinder and that one overflowing was only caused by that carb being out of spec or damaged in some way. Turns out these on the 550 are linked by a connector that'll allow fuel to flow from one to another while bike is leaned over without causing the out of spec one to run fuel out the overflow. Carb number one was overflowing because of other floats being out of spec and letting gravity take its natural course and letting fuel go down hill overfilling number one and causing it to leak while on side stand and making bike run rich and flood while riding. I learn something new with every project bike I bring back from the dead. Hope this helps anyone with a similar carb issue.