My carbs are driving me nuts - GS850

[AJ]

Pull your gas cap apart again, if it is not venting your bike will starve, but my money is on water in the gas.
fwiw

Y'know, that's not a bad thought. As you pulled more gas, you'd start to unport the water sitting on the bottom. At a minimum, open your drain screws and drain the bowls. This will also let you see if your petcock flows on the prime setting.

[49er]

One of my diaphragms was a little marginal. It was very wrinkly and I had to fuss with it to get it seated. I did pull the cover later and found it still seated. I don't think the slides are an issue at this time. I'm betting on fuel.

I guess you've got a later model engine or head on your '79 850. The original carbs were manual slides (without diaphragms).

Give your tank a through checking over for a clogged petcock filter. If you have an inline filter, ditch it and try again.

Failing that, my money is on clogged pilot jet circuits from leaving the bike sitting too long between runs. You can isolate this by checking if all the headers are hot. If one is cold at idle, that is the carb that needs additional cleaning of the pilot circuit .

[86turbodsl]

Pull your gas cap apart again, if it is not venting your bike will starve, but my money is on water in the gas.
fwiw

I tried pulling the cap when it was running. No change.

[86turbodsl]

Update: I fiddled with the fuel line and got it shorter and so there wasn't an air bubble in it. I verified that the petcock has full flow on all settings. Put it all back together and took for a spin. It was better, but still had the same issue. Acted like it was running out of fuel at low rpms. If I could get it up in the rpms, it ran more normal. My last act for the evening was to run and get a few gallons of gas. I dumped the gas into the bike and took it for a spin. To my surprise, it acted almost normal. Just a little bit of surging, but nothing major. So apparently the problem is sensitive to fuel pressure. My reasoning is that more gas means more fuel pressure due to increased fuel level / delta Z. I took it out for a couple of miles, far longer than I was able to before the new gas. It ran the same when I got back as when I started. So what makes the pilot circuit so sensitive to fuel level in the bowls? And why would more fuel pressure fill the bowls better? Restrictive fuel inlet valves? Crud build up or something on the screens? Wouldn't that prevent ALL circuits from working correctly? I'm stumped. Anyone have insight?

[tom203]

Enough thinking- just ride it some more to refresh it's memory! When I bought my bike, it had sat out two riding seasons- it ran OK, but improved noticeably after a couple of tankfuls.

[86turbodsl]

Easy for you to say, you're not the one getting stranded!

[btbarb]

Reserve

Maybe you were just on the line between normal and reserve, mine wants to be switched to reserve with about a gallon or so left.

[tom203]

Easy for you to say, you're not the one getting stranded!

Negative vibes! You don't have to take off on long trip- my first maiden trips were within 10 miles of my house. Just get it up to normal operating temp and run some gas thru it to convince it you're serious!

[86turbodsl]

Bryan - no I tried it on reserve too. No change.

Tom - point taken, didn't mean to be negative. I couldn't get much beyond a 1/2 mile away from home before. I'll try and run some more gas through it next couple of days.

[7981GS]

Throw an entire (15 once) can of Berryman's B-12 carb cleaner in the tank and fill with premium fuel.
Run it around the neighborhood for a good long time keeping close to home with cell phone in pocket.
She just might clean up and run great.
Do you have good clean spark plugs in it gapped to .028"?

Eric

[86turbodsl]

Yep, done the entire maintenance schedule by end of year last year. new plugs, everything.

[chuck hahn]

Yeah on the B-12..but if your near a freeway I would jump on and go up about 20 miles or so and turn around. The 40 miles round trip will do 2 things..get the bike good and warm and run the gas thru the carbs at a faster rate and the B-12 also. gives them a better scrubbing that way..in my opinion ajyway.

[btbarb]

Yep, done the entire maintenance schedule by end of year last year. new plugs, everything.

I see you checked the petcock flow and settings into the catch can, but I didn't see you note yet (maybe I missed it?) if you ran the bike with the petcock on PRI, maybe there's a crack in your vacuum line that keeps the petcock from opening properly, running on PRI would take that variable out.

[chuck hahn]

He did say he tried the prime setting..post 13.

[Blastr2783]

Took mine to Orions this morning and told them fix it. I have never had this much trouble getting carbs right.