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.

 

[Guest]

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.

 

[Guest]

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.

 

[Guest]

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?

 

[Guest]

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!

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?

 

[Guest]

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

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

 

[catbed]

my carbs are not very clean, but the passages are open.


just re-cleaned them. will post tomorrow when i get a chance to start the bike.


stripped 3 of the pilot jets including one i couldnt get out.

time to look for some new ones.

 

[salty_monk]

You could try running some seafoam through it... it wouldn't hurt. Found some at Kragen today.

Dan

 

[Matchless]

Hi, if you have not removed the pilot screws and the pilot jet (Under that rubber plug) and pushed carb cleaner through the passages and cleaned the pilot jet while out, your idling circuit may still be blocked.
It took me three try's initially before I found a small bit of loose gunk inside the pilot jet that was laying down and flipping up at times, I had to break it up with a copper wire and then it only came out when the carb cleaner was put to it.
On the CV's there you have an Air Pilot Jet with a biggish hole on the side of the airbox side. Then a Pilot Jet with a very small hole (see BassCliffs picture) quite deep in a tube under a rubber plug hanging down into the float bowl. The very thin brass tube is the fuel pickup to the choke or starter circuit. The idle circuit then has 3 very small holes close to the top lip of the butterfly on the engine side. One of these are adjustable with a Pilot Idling Screw that has a very small o-ring and washer and a spring around it and a very important and thin tapered tip. If someone has sprayed carb cleaner or some other rubber unfriendly substance on this tiny rubber o-ring it may have disintegrated already
The tapered tip of these Pilot Screws are known to become stuck and even break off, meaning that the adjustable hole for the idle mixture is then completely blocked. I personally have never encountered one so I am not sure if it is due to corrosion, such as water of a cleaning chemical getting past the threads or just ham fisted tightening. As a precaution I put a small amount of waterproof grease on the very fine threads of the pilot screw after cleaning and replacing the o-ring
You must remove those Pilot screws and make sure the idle feeding holes are open and that the Pilot screws are in good working condition and that an air fuel mixture can reach these holes via the Air Pilot jet and Pilot jet and that the Pilot screw can adjust this mixture.
You will have to check this on each carb and it cannot be done if the factory caps are in place, you will have to remove those.
There are some other ways of cleaning a carb in situ, but on a 4 -rack, rather remove, strip them down completely (this means that every rubber and other component and jet must be removed, clean each component meticulously, initially with clean fuel, then by spraying carb cleaner through all orifices not just into it, but it should shoot out the other side, as well as high pressure air. This is stage one. Now you can even boil the carb in clean boiling water with a bit of lemon juice for flavor (read that thread)!
Use this opportunity to check all the components for wear, diagrams rubber, needle slides, needle & seat.
Definitely replace all o-rings, especially if they are out of shape or brittle.
now reassemble carefully and make sure that your idle screw is backed out about 1 and a half to 2 turns. Give attention to the float height as well as this is a VERY important adjustment. Also if a PO has messed around with the carbs you may want to bench sync the throttle openings before hanging the rack.
Then finally if you really want to do yourself a favour replace al the japanese crosshead screws with metric allen stainless steel ones. the removel and stripping really becomes a breeze as you use T handle allen key wrenches.
I hope this motivates you enough to pull them apart completely. I was also daunted by this the first time. Print the guides that are available on the forum if you are wary of doing this, but believe me there is no shortcut, it sometimes is just luck if limited cleaning sorts a problem.

 

[catbed]

does it help if i say the throttle makes it die?

or does it still mean those darn pilot screws. where does the gas go from the pilot screw?

 

[catbed]

it idles on numbers 3 and 4 but 1 and 2 are warm. i fiddled with the mixture screws and now it idles without choke. but, same as before still dies when i touch the throttle. this is getting really frustrating. i am ordering new pilot jets and new main jets. i think i may dip the carb to clean it and get new o-rings. any ideas before i do that?