Running rich?

[barrelguy]

1980 xs1100sg, 24,000 miles, pretty much all stock.
I have a feeling the old girl is running a bit rich - black, sooty plugs, gasoline odor in the exhaust, crappy mileage. I have gone cross-eyed looking at all the carb threads trying to figure out if there is a quick and easy method (screw adjustment) to adjust the mixture without dismantling half the bike and all the carbs. I did run some Seafoam through the tank a couple of months ago. Other than this the bike runs very well, lots of giddy up when I need it, easy starting, idles fine.

Thanks for any input.

[3Phase]

Barrelguy, have you checked and cleaned the air filter?

Do you still have the vacuum controlled fuel distribution valve (octy) on your bike?

If you leave the fuel taps set to the Prime position does any fuel leak out of the carburetors?

[barrelguy]

Octy is still in place, air filter is clean, no leaks with petcokks on prime.

[BA80]

Has it been ridden much? I mean considerable distances.

It may just need the cobwebs blown out of it, so to speak.

[barrelguy]

Just been doing some around town stuff with occasional highway runs of 30 - 50 miles. For the record my gas mileage has never been great; around 90-100 miles when the light comes on. Maybe I'll go for a nice long ride this weekend to see if that helps any.

[BA80]

90 - 100 miles is about the norm for a special with mixed in town and highway riding. With the fairing and bags your carrying a lot of extra weight with more wind resistance.

Mine gets 38 - 40 MPG ( aproximately 120 miles) on the highway if I keep the tach between 4 and 5k. Over 5000 and mileage drops considerably though. Love the 850FD for highway trips. Good cruising RPMs at about 75 or 80 MPH.

[barrelguy]

Thanks for the input guys - always good to know. However I really would still like to know the whereabouts of the elusive mixture adjustment screw for future reference. Cheers.

[BA80]

On the 80 model it's at the front of the carb on top near the intake boot. It's down in a recessed hole there. 1980 had Ralph Nader all over it so the mixture was preset at the factory and was sealed.

Yours are probably still sealed if you can't see them. The caps can be removed fairly easily so that they can be adjusted. Adjusting them though is not all that easy.

[barrelguy]

Thanks BA

I'll pop the tank off tonight if I find a few minutes and see what I can find. As far as adjustment goes, is it 'in' or 'out' to lean the mixture?

[BA80]

In will lean it out but that's pretty much just at idle. If you have never gone through and cleaned those carbs that's probably where the problem is.

Try running another can of seafoam through it and put some good miles on it before you mess with the carbs.

Of course that's just an opinion of someone on the other end of your keyboard.

[barrelguy]

Thanks again,

I'm trying to avoid doing an in-depth dismemberment of the carbs right at the moment so I'll try another round of Seafoam and maybe try to schedule a trip to the coast to visit Momsie (1000 km round trip).

If I didn't value the opinions of those at other keyboards I wouldn't have asked!! Always lots of unselfish folks here ready to help out I'll let you know how it goes. Perhaps someday someone will ask about something I can help with. Mind you, that kind of limits the topics!

[melbxs]

Barrelguy

Get hold of a Gunson Colortune. (look on EBay)

I manually adjusted my mixtures using all the guides etc. but when I used a colortune I got them spot-on and the difference in the way the bike runs at lower rpm is incredible.

It's a 30 minute job and doesn't involve dismantling anything.