Running out of things to look for

[VP1]

I just don't know what to do...
Some of you may remember my previous threads about trying to get the idle correct on my 82 GS850G. It runs well in the higher RPM range but won't hold a steady idle/ doesn't always return to idle smoothly. It hangs a bit and sort of acts like an air leak. After I rev it up, the times it'll return to idle smoothly, it then drops to a lower idle and will usually eventually die.

So far I have-
Rebuilt/ cleaned the carbs
Replaced carb o-rings and intake o-rings (except choke o-ring, can't get the choke assembly nut off)
Sealed airbox
inspected boots- they all are ok- no cracks
Synced carbs (finally gave up and bought sync tool)
New petcock

I'm running out of things to do. I still haven't checked my valves though. I'm going to check the valves today and replace the plug caps also. I don't know what else to do... This is frustrating and disheartening to say the least..
-Todd

[Nessism]

How many turns out are your pilot screws?

[Larry D]

Read bwringer's post. It may help.

http://www.thegsresources.com/_forum/showthread.php?t=135728&page=2

[GQROD]

Don't lose heart, you have to be methodical.

I didn't read your prior posts however this may help sort things out......

Did you check the AIR jets to make sure they are matched to your fuel jets? Are they clean?

Is the tank full of fuel? ( sometiems you get to half tank the engine shuts off cause the petcock lever has to be in the reserve position. )

Is the petcock in the correct position meaning prime then on or reserve if you don't have a lot of fuel in the tank while tuning.

Are vac hoses getting kinked when you put the tank back on?

Is your fuel line getting kinked when you put the tank on?

Do you have the correct size jets in your carbs? on mine i had to go up one on my pilot jets in order to get a good steady idle from the stock 35 to 37.5

Are you absoulutely sure all the carb passages and jets are clean?

Is your choke cable and throttle cable adjusted properly?

Are the bowls full of fuel?

Do the valve adjustment pronto!

Did you bench sync the carbs before you mounted them per the factory manual?

Are your plugs gapped properly? Are they new?

Did you do plug chops to determine what color the mixture is? this will lead you to the problem right away.

As was already asked how many turns are your fuel screws?

How many turns out are your air screws?

Have you adjusted the throttle with the throttle stop screw to get the correct idle?

Once all these questions are answered you will no doubt be closer to finding the problem just take one step at a time and eliminate as many issues as possible remembering what happened after each step was taken ie: did it make the bike run better or worse?

Hope this helps

[VP1]

Thanks guys, i'll answer all of the questions in just a little bit.

One question first though- Can anyone confirm that my bike has fuel screws? I know it has airscrews but I'm pretty sure there are no fuel screws.

[Nessism]

I always thought were called Pilot screws...and yes, your carbs have them.

[Dave8338]

I'm running out of things to do. I still haven't checked my valves though. I'm going to check the valves today and replace the plug caps also.

This would have been first on my list of things to do.

That being said, once the valves are set, it can only be a mixture problem and they are quite easy to sort out. Too much air or too much fuel.

[Larry D]

I always thought were called Pilot screws...and yes, your carbs have them.

I call them idle air adjustment screws....hopefully there isn't a broken off tip in one of the carbs. Don't ask how I know....Don't screw these babies in with gorilla torque !! Just "lightly" seat them and adjust out from there.

[VP1]

This would have been first on my list of things to do.

That being said, once the valves are set, it can only be a mixture problem and they are quite easy to sort out. Too much air or too much fuel.

I know I really should have done that sooner. Everything I've heard indicates that while the adjustment is important, it really doesn't affect the problem I'm having- hence my putting it off. I'll check them today though.

Same thing with the spark plug caps. didn't think they'd produce these symptoms but I'll replace them too.

As for the air screws- Ok, I definitely know my bike has those, but in some previous threads and also now in this thread I've heard FUEL screws mentioned which as far as I know my bike does NOT have. Anyone able to confirm that? I've had the carbs apart 3 times now so I'd think I would have spotted them.

BTW- Air screws are 3 turns out

[Matchless]

There is a bit of confusion due to the various names for this screw, idle mixture, air screw, fuel screw, more correctly pilot screw.
In actual fact on the CV carbs this screw adjusts the amount of fuel in the idle circuit and the amount of air for the idle mixture is static as per the idle air jet. Lean in and rich out.
Idling rpm's changing -check for leaks on the rubber intake boots and the airbox boots as well, especially if they are hard and not sealing well.

[BassCliff]

Hi,

There's just the one screw on top. This is from the Carb Cleanup Series notes:

Note #2: Bill Kingston has brought it to our attention that the references to a Pilot Air Screw may be incorrect. He states that on these carbs use a Fuel Flow Screw instead. This means that you are controlling fuel running through the passages with this adjustment, not air. So when turning the screw counterclockwise you are increasing fuel flow and when you turn it clockwise you decrease fuel flow.

I thought you were supposed to start about 2 1/2 turns out for the 850. Are your needles and jets in good shape? I don't have the pictures handy, but check them for irregularities, pitting, grooves, flat spots, etc. And check those valve clearances as soon as you get a chance.

As for the air screws- Ok, I definitely know my bike has those, but in some previous threads and also now in this thread I've heard FUEL screws mentioned which as far as I know my bike does NOT have. Anyone able to confirm that? I've had the carbs apart 3 times now so I'd think I would have spotted them.

BTW- Air screws are 3 turns out

Thank you for your indulgence,

BassCliff

[Nessism]

If the idle mixture is too lean a hanging idle can result. Try 2.5 turns like Cliff suggests and then tweak from there.

[VP1]

Air screw, pilot air screw, fuel screw- whatever you want to call them, they're 3 turns out

[Steve]

Air screw, pilot air screw, fuel screw- whatever you want to call them, they're 3 turns out

At 3 turns, you should have plenty of idle mixture in there. Have you adjusted the valves yet?

Just one more statement of fact and an opinion on screw nomenclature:
My Suzuki manual calls them "Idle mixture adjustment screw[s]". The idle mixture on the VM carbs is controlled by the pilot fuel screw (under the carb) and pilot air screw (on side of carb). You have to tweakone or the other to adjust the mixture, and both of them to adjust the quantity of the mixture. With the BS carbs like yours, the mixture is controlled by fixed jets. The air jet is in the intake throat and the fuel jet (pilot jet) is in the float bowl, next to the main jet and needle jet. The screw that we can adjust only adjusts how much of that pre-set mixture gets into the air stream at idle and very small throttle openings. Personally, I think this arrangement is easier to tune for street bikes.

Now back to the 'help' section:
To help you with your valve adjustment project, send me an e-mail with a request and I will send you a copy of my Excel spreadsheet that will help you do the math to figure out what shims you need. It will also help you keep track of what you have in there from one adjustment to the next.

Just in case you have not yet discovered this little feature, click on my name, you will see information on how to get my e-mail address.

.

[GQROD]

Take everyone's advice to heart, these guys know what they are doing if it wasn't for them my bike would be in the junkyard by now.

You may not think one thing is the solution to the problem but on these bikes there is no one definite cause to any problem.

Rather eveything has to be right in order to get the bike to start, idle and run right so only going through everything will the adjustments work.

Hope it works out!