idling on choke

[catbed]

i finally got my 850g idling. couple problems though. it only idles on choke. when i take the choke off it immediately dies. at full choke it gets up to about 3.5k rpms but it goes up and down between that and 1k.

whenever i touch the throttle even the tiniest bit, it sputters and dies.

my clutch does not fully disengage i think. i tap the starter button with it in gear and the clutch in, and the bike rocks forward a little. is it just sticky?

i think only the two outside cylinders are firing, because i touch the exhaust pipes and the outside ones are hot and the inner ones are warm.

sorry for some stupid questions, its my first bike.

[psyguy]

i'd check the coils, cables, plug caps first
take the sparkplug out and plug it into the cap, hit the starter button to see if there's any spark. have the body of the plug touch the engine.

[catbed]

i checked that before and i saw a spark.

[psyguy]

well, if you're getting a spark but the exhaust is cold, it means either you're not getting any fuel or the fuel/air mixture is badly wrong
did you set all the mixture screws correctly?

[catbed]

i didnt touch the mixture screws. they have the caps on them still.

[psyguy]

also, it helps if you tell us all the work that's been done or all the things that you already eliminated as a problem
like, your carbs may be blocked, dirty
or your coils or cables/caps might be failing
or really bad compression
etc

[catbed]

i took the carbs apart and cleaned them. it started idling after i cleaned the two choke pipe things in the bowls of the carbs. if i clean the other two, do you think it will idle?

[psyguy]

most definitely, when you clean your carbs, make sure to clean ALL of them equally well
if the cleaning of the two carbs helped the CORESPONDING cylinders to work ok, then most likely you'd get good results by checking the other two for the similar problem (clogging)

[Matchless]

As psyguy said it is fuel, especially if you have proved the spark is present! If you have CV carbs and they have never had the idle mixture screws out in 28 years, then it is quite possible that the pilot jet or pilot circuit is dirty or blocked, as this circuit in the carb controls the idling. The bike will not idle on only two carbs and the cold exhausts point to the possible culprits. If idling on choke is erratic, then make sure the two cold carbs have fuel in the float chambers, may have sticking needle there.
You will not go wrong in pulling the carbs, stripping them, cleaning properly, replacing all the o-rings and also checking the boots, replace intake o-rings as well while you are at it.

[BassCliff]

Hey howdy hey!

Mr. catbed,

There is a "right of passage" necessary to get these classic bikes back to their former low maintenance, bullet proof glory. I believe Mr. bwringer said it best. (Note: Although this is GS850-specific, most of the information still applies to all GS bikes.)

----------<quote Mr. bwringer>----------
Every GS850 has (or had) a set of well-known issues that MUST be addressed before you have a solid baseline for further troubleshooting.

It's a vintage bike, and it's quite common (as in, every single GS850 I have had contact with) that there are multiple problems that have crept up and slowly gotten worse over the years.

It's not like a newer vehicle, where there's generally one problem at a time.

These common issues are:

Intake O-rings (install NEW OEM or Viton only - common nitrile o-rings will quickly deteriorate from heat)

Intake Boots (install NEW -- these cannot be repaired)

Valve clearances (more important than most people think)

Carb/airbox boots

Airbox sealing

Air filter sealing

Petcock (install a NEW one)

On '79 models, install new points or Dyna electronic ignition (or at least verify that the old points are working correctly)

On all models, it's fairly common to have problems with the spark plug caps. These are $3 or $4 each, and often worth replacing if you're keeping the stock coils/wires.

Stock exhaust with NO leaks or holes -- good seals at the head and at the junctions underneath.
----------<end quote>----------

The best carburetor rebuild procedure is located here.
For your electrical needs read the Stator Papers.
Mr. bwringer also has some great repair tutorials on his website.
Mr. robertbarr has lots of necessary parts for carbs and such on his website.
And yours truly has a few pictorial maintenance guides (oil change, valve adjustment, etc) on my little website.

If you can't find what you're looking for in the above links or by using the search feature in this forum, just ask. The collective experience here is nothing short of phenomenal.

Thank you for your indulgence,

BassCliff

[catbed]

now only 1 cylinder doesnt fire and that cylinder's carb backfires. valves maybe?

still only runs on choke and i cleaned the other two carbs again.

[catbed]

any suggestions?

[psyguy]

tell us the history of any work done and things that you have eliminated as a possible cause
if you are getting better and better results checking and cleaning the carbs thaen as matchless had said take them appart, etc

[catbed]

This is all i did:

Cleaned all of the carbs twice.
Checked for sparks on all the spark plugs.
Cleaned all of the spark plugs.
replaced petcock. (there is fuel in all of the bowls)
the breaker points are fine, just looked at them, no dirt or dust.

where do the pilot jets get the fuel from? i know there are rubber caps on them and mine look like they melted(old gas, maybe) where does it go also. ill try cleaning that again.

[BassCliff]

Just being thorough

Mr. catbed,

It sounds like you've got good spark. In cleaning your carbs, have you followed this procedure and cleaned them really well, including doing this?




If your carbs are really clean, have new O-rings installed and have been bench-synced, then perhaps it's time to make sure the air intake system is sealed up properly (new carb boots and O-rings, new weatherstripping around both side panels of the airbox and on top of the air filter cage, etc) and make sure your valves are adjusted properly.

Note: It seems that Mr. robertbarr's website is not working at the moment. He's got all the internal o-ring bits you need to get your carbs back into shape.

Keep us informed.

Thank you for your indulgence,

BassCliff