Sooty plug 1980 GS1100

[Anonymous]

Hi

No. 1 plug remains sooty after I reduced the air-fuel ratio using the air balance screws on the carburetor tops. I have the screw on No. 1 all the way down with no improvement on the plug color. So, can I remove the screw jet on No. 1 with the carburetors still on the bike (remove the tank)?

If so, I was thinking I could check for foreign material in the carburetor without having to remove the carburetors (I reckon I could remove the float bottom from this carburetor while it is on the bike to check for float height as well).

This site is terrific and I have found a lot of invaluable information.

Patrick

[focus frenzy]

the idle air screw only adjust the mixture at idle, screwing it down richens the mixture at idle compounding your problem.

check the float level, these carburators can be finniky about the fuel level in the bowls, also check to make sure the rubber plug that sits in the opening in front of the main jet is there and sealing good.
if this plug is missing fuel will bypass the main jet and it will flood bad on that carburator.

[Anonymous]

Sooty plug on 1980 GS1100

Hi.

I thought that turning the screw down leans out the mixture (it worked on the other three carbs). All four plugs were badly sooted up last week when I started to sort this out. I have the others running very clean now.

I had the carbs rebuilt last autumn as the bike was in storage for 20 years and all plugs were fouling when I got it running - I thought the guides/seals needed replacement but learned that the carbs probably just needed adjustment - learned it here last week.

I started with the screws out about 1.5 turns and it would not idle at all so ran them out a bit and it almost idles now although not very smoothly.

I made sure the rubber plugs were in place when I checked the floats when I had the carbs off last week.

One thing I was a little concerned with was some green staining on these little (copper?) standpipes projecting down into the float chambers. I tried to clean the stain off and the very small holes in the standpipes looked to be clear - what are they for?

Thanks for your input and I surely do appreciate the help.


Patrick

[moto_dan]

Re: Sooty plug on 1980 GS1100

Hi.

I thought that turning the screw down leans out the mixture (it worked on the other three carbs). All four plugs were badly sooted up last week when I started to sort this out. I have the others running very clean now.

Patrick

If the adjusing screw is on the engine side of the carb then you're correct... in is leaner.

[chuckycheese]

Pilot jet

I bet your problem is with the pilot jet. You're lucky the problem is on #1 because it's easy to get to. You can pull it fairly easily with the use of a small hand mirror and a couple of short-handled screw drivers. It's a little bit awkward but taking the carbs off, at least on my bike, is an absolute nightmare. At the same time, I'd back the idle screws out between 1 1/2 and 2 turns and go from there. Good luck

[focus frenzy]

Re: Sooty plug on 1980 GS1100

If the adjusing screw is on the engine side of the carb then you're correct... in is leaner.

My bad, mine still has the seal caps on.