No idle

[stovall56]

I'm in the process of resurrecting my '80 850G. We went through the carbs, and had it running OK (low on power, but running smoothly). We ran into a charging issue, and then life got in the way, so we let it sit for ~4 weeks. We came back to it, fixed (I think) the charging issue, and cranked 'er up again. Now it won't run below 3k rpm. Just dies immediately. Runs smoothly above that, but not at all below. I know that the tank is rusty, and that could have caused this, but I was hoping that my inline filter would have stopped the rust. I guess I'm having difficulty believing that the fine rust that can get through would have such a dramatic effect, so I'm looking for ideas. Rust, or other problems?

Thanks.

Mark

[snark]

Sounds like dirty gas or an air leak. Did you change the boot O rings?

[almarconi]

It's a shame you didn't clean the tank BEFORE cleaning the carbs. Your pilot circuit is probably clogged with crud. The inline filter probably is clogged also. Did you also check that your battery is charging properly and you have adequate voltage at the coils? Sometimes ignition problems will have similar symptoms as fuel problems.

[stovall56]

Both sides (airbox and engine) have new boots, and o-rings where applicable.

Yeah, I now realize cleaning the tank should have been a higher priority. Just changed the inline filter, and that did no good. As for charging, I'm a little confused by that, since I'm not getting the good 14 volts at high rpm (more like 13), but it does seem to be charging (higher voltage on the battery after a ride than before it). Either way, it's not low enough to kill the engine.

I'll check around some more for air leaks, but it sounds like rusty gas is the early leader for "probable cause".
I just want someone to tell me I don't have to pull those stupid carbs AGAIN.

[Nessism]

You need to check the battery voltage with the engine running and the engine reved up to about 3000 rpm or so - should be in the range of 14-15 volts.

When you cleaned the carbs did you break them down and soak in carb dip?

[stovall56]

That's how I was checking voltage. Not sure why it wasn't coming up to 14.

We broke down the carbs as best we could. Never managed to get the air screws out (they were stuck big time), so we dipped 'em such that the air screws were never submerged. I would call that an incomplete dip, but it was the best we could manage. Yeah, that's probably causing us some problem, but not this one, since it idled at a reasonable tach speed after the carb dip, but not after the ~month of sitting.

Mark

[spchips]

Have you done a valve adjustment?

[Buddy]

Have you changed plugs? I've had 2 sets of "OLD" plugs run good for a while, then go bad with simular symptoms.

[BassCliff]

Greetings and Salutations!

Hi Mr stovall56,

If you are using a fuel filter, make sure it is a gravity-fed filter and not one designed to be used with a fuel pump. A lot of riders use lawn mower fuel filters, or similar, if necessary. Many other riders, myself included, do not use inline filters because of fuel starvation issues. Either way, you definitely need to get that tank cleaned. The mesh filter at the top of the petcock can become clogged as well.

For more GS basics, please visit the mega-welcome page on my little BikeCliff website, and help yourself to lots of GS850G lovin'.

Thanks for joining us. Keep up the good work.


Thank you for your indulgence,

BassCliff

[stovall56]

I have not done a valve adjust, or changed plugs. I'll certainly try the plugs. The valve adjust will require some more research, as I've never done one.

As for the filter, that may be a problem with the new filter, but the same idle issue existed with the old filter, which I had been running for quite a while before the problem cropped up. I was inclined to remove the filter to help diagnose this problem, but scared to because of the rust in the tank. I'll get to work on cleaning the tank to at least eliminate that concern.

Mark

[BassCliff]

The valve adjust will require some more research, as I've never done one.

Hi,

I've documented all of my research into valve adjustments. Just visit my website and save yourself the trouble. Download a manual while your there.

Thank you for your indulgence,

BassCliff

[stovall56]

I know this thread is a little stale, but in case anyone was curious:
Shortly after I started this thread, a hurricane came through our town, and my garage flooded. The GS was in two feet of water. It's done. It isn't worthwhile to me to try to rebuild it now. So, unless someone's near Houston and wants to acquire a project bike, we'll never know what was causing it to run roughly.