Way to rich

[mark]

I wish I was a rich as this bike. Its a "79 85GS. I've taken the carbs apart and cleaned them, checked the choke etc. Airbox off, on, whatever, black sooty (not oily) plugs after about 10 minutes and lots of smoke, backfiring through the carbs etc. Starts instantly, runs good and then starts to sputter and smoke like the choke is on (it isn't)! Puffs of smoke from somewhere between the motor and the carb on no. 4 and a pop once in a while. Bike runs way better with the vacuum line to the gas tank unplugged.

Vacuum on the bike is very poor, 2 or 3 psi at idle. Compression around 125 psi on all cylinders. Timing and points etc, recently replaced. Float drop is what its supposed to be.

Who knows what the person who had the bike before me did. Is there a way to experiment with leaning this thing out a bit? Sheez.

 

[KEITH KRAUSE]

Re: Way to rich

Bike runs way better with the vacuum line to the gas tank unplugged.
Who knows what the person who had the bike before me did. Is there a way to experiment with leaning this thing out a bit? Sheez.

What do you mean "unplugged"? Disconnecting the vacuum line from the carb or petcock, or ?
You never know what a previous owner has done. Could be a lot of things.
You say you've cleaned the carbs and the floats are set, points and spark are good. A few more easy to check things:
Are the sparkplugs NGK B8ES or equivalent? Are they gapped right?
Is the air filter clean?
Have you adjusted the pilot screws (underneath/front of the bowls), or the side air screws?
The side air screws are to be set for the highest rpm's. They are GENERALLY out about 1 1/2 to 1 3/4 turns.
The pilot fuel screws are not as easy to get right if they've been moved. For starters, you could try them at 3/4 turns out if the bike has the stock airbox and lid. If you do adjust the pilot or air screws, be aware they can be tight and the heads stripped easily. Use a good fitting tool. If you seat the sharp-tipped pilot screws, do it LIGHTLY so the tips don't break off inside. Keep a record of how far out all screws were set, including any adjustments you make. Turning the pilot fuel screws OUT, richens the mixture. Turning the side air screws OUT, leans the mixture.
With these screws set as I said, the bike should run "in the ballpark" if the screw settings were way off to begin with. More tuning would be necessary of course.
If this doesn't help, then you'll have to check if the jet needles have been raised, main/pilot jets changed, poor o-rings inside, etc.

 

[mark]

Way to rich

Thanks for the help.

I meant "disconnected".
We'll see how this goes. Thanks again.

 

[mark]

Way to rich

Well, as it turned out, the side air screws were nicely tightened up.....and I think I might have done it. The bike is running a lot better, not great, but at least I can see again. Thanks, you guys are on my Christmas list.

 

[KEITH KRAUSE]

Glad to help.
Your comment about the bike running better after disconnecting the vacuum line to the gas tank still doesn't make sense.
Pulling the vacuum line off the petcock would create an intake leak, unless you plugged it. But with no vacuum at the petcock, the fuel wouldn't flow through it, unless you had it on "prime". And if the bike ran better on prime, that would mean you have a fuel flow problem. Either a clogged petcock passage, damaged diaphragm, or a cracked vacuum line.
This would be a seperate problem not related to the too rich mixture.
As for the side air screws, they should be adjusted for the highest rpm's.
Put the bike on the centerstand and warm it up first. With the screws out about 1 1/2 turns as a starting point, start with carb #1. Turn the screw an additional 1/4 to 1/2 turn out and listen for the highest rpm's. You may have to go back and forth a little. Somewhere between 1 and 2 turns out will be the sweet spot. Just stop turning when the rpm's max out. Now set the idle (if necessary) to about 1,100 rpm's by turning the idle adjuster knob. Go to the next carb and set it the same. Now re-set the idle again...do this to all 4 carbs.