'78 kz750 twin - seafoam causing stall in one cylinder?

I had been running with a 40 year old coil for a few weeks before replacement that caused plenty of fouling. So, I got some seafoam carb spray and sprayed about half the bottle into the right cylinder while revving causing the usual white thick exhaust. No hesitation on this cylinder. I shut the engine off to let it sit in that cylinder, then put the nozzle into cylinder 2 to repeat the process. I started the engine and sprayed just a bit and the engine died. Started it back up and revved to about 3-4krpm and tried to spray again, the engine bogged and died. Tried it about 3 more times and it died as soon as I sprayed every time.
What does this mean? I now have a hopefully clean one cylinder, but the remaining cylinder will just NOT take this stuff.
Should I think of a different way of cleaning out this cylinder?
What could cause one cylinder to accept cleaner and not the other?

Not sure what the problem is but I'm pretty sure spraying that stuff into your engine does nothing useful .

Ok. So to really clean these cylinders, should I take off the head and get in there with a brush?
This also makes me worry a bit, because I know that each cylinder should run independently. I have taken off a spark plug wire while running and had one cylinder at a time run by itself. Even if one cylinder fails, the other should stay running! Right?

Why are trying to clean your cylinders, they don't get dirty.

I've read some spray a mix of water and anti freeze in the carbs while reving...... Regaine by Gum out is suppose to be pretty good also running it in the tank.... but neither will do wonders ...... Really don't think you should worry enough to take it apart to clean.

baldy110 wrote: Why are trying to clean your cylinders, they don't get dirty.

This.


Unless the rings or valve stem seals are bad, or the bike has been ridden for a bunch of miles with the fuel mixture wickedly rich, the combustion chambers should have no serious buildup of carbon. If any of those conditions exist, flooding the cylinders with chemicals or water will not correct them.
You say the exhaust was white and thick. That would be the Seafoam. Carbon is black, not white.
How did the engine run with the new coil and new sparkplugs?

It runs a ton better with the new coil. No misfiring anymore. But there's no telling how many miles were driven with the bad coil that was causing fouling. There's a total of 10k mikes on the bike. I know I rode about 600 or so miles with fouling. When I put a finger into the intake and look I can see and feel a rough and almost sticky surface in the cylinder. Will this clear up? It doesn't seem like it could just go away on its own.
I'll do some further tests on the cylinder in question. Like trying to get it to run on it's own and checking the new plug for new fouling evidence.

Jessmansimon wrote: ....................... When I put a finger into the intake and look I can see and feel a rough and almost sticky surface in the cylinder. ......................

I do not understand how one could put a finger through the intake and feel or see anything inside the cylinder. If nothing else, the intake valve would prevent one from doing this. Please explain further. Ed

It's normal for there to be some carbon. I wouldn't worry unless it was running pig rich for many thousands of miles.

Oh I just mean the metal passage from the carb throats to inside the cylinders has a rough coating and looks brownish, and also when I look down the spark plug hole, the same coating is present.