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Help with Carbs - 1982 GS650G

  • Thread starter Thread starter philosopheriam
  • Start date Start date
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philosopheriam

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Folks,

Before I get flamed, I did a search, and all I am asking for is some clarification and some advice.

Before I begin, I'll make a long story short - I followed the carb cleanup series for a 1982 GS650GL with Mikuni carbs.

After reassembling the carbs, I put them on the bike WITHOUT THE AIRBOX - I now realize that this may be causing some of the following problems:

I set the "air screws" to 2.5 turns out from lightly seated. Correct me if I'm wrong, but there are no other adjustments on this carb other than the "air screw" ???

Question 1:
Does the "air screw" increase air or increase fuel as it is turned counterclockwise?

Question 2:
The bike started just fine, however, when I snap the throttle multiple times it starts to bog - could this be caused by me not having the airbox on and not enough vacuum being pulled to open the slides properly?

Question 3:
I screwed in the pilot jets until the were snug in the carb body - these don't have an adjustment, do they?

Question 4:
How many turns total do people usually have their "air screws" the bike seems to be running pig rich at 2.5 turns (granted, this is with the airbox off)

Please help, as I'd like to have this bike done already!

~philosopheriam



I'm using a test fuel tank, fyi
 
I'm sure other folks more expert than I will chime in, but I'll start with what I've learned so far. If you don't do these things, you're just wasting your time.
  1. The airbox MUST be installed, with the correct filter.
  2. There must be NO leaks that will allow in any air except that which passes thru the filter. This includes thru the boots between the air box and carbs, and between the carbs and the head. It also includes making sure the airbox itself is competely sealed.
 
I installed new viton orings between the intake boots and the heads.

Also, I checked the air screws to make sure the tips werent broken and I set them to 3 turns out.

I also checked to make sure all the slides operate freely, etc.

I was concerned, as when I started the bike smoke was pouring out the pipes - I chocked it up to all the wd40 I sprated in the cylinders after the petcock failed and filled the #1 cylinder with fuel.

I checked the clearances on the valves and they were on the low end, but seemed ok.
 
Like was already said, put the air box back on with the correct filter. Then, get a carbtuner to help you set things. Then adjust to the, I think it's called, highest idle method (I still have to work on mine again) where you notice the idle changes as you turn the screw.
 
Well, I reinstall the carbs tomorrow witht the airbox and give her a whirl...

I'll leave the air screws at x3 turns and see what happens.

But as I asked in my original post, the air screws are the only adjustment on these carbs, right? And counterlclockwise goes which way - lean or rich?

Thanks!
 
philosopheriam said:
Well, I reinstall the carbs tomorrow witht the airbox and give her a whirl...

I'll leave the air screws at x3 turns and see what happens.

But as I asked in my original post, the air screws are the only adjustment on these carbs, right? And counterlclockwise goes which way - lean or rich?

Thanks!
Click to expand...

Yes, rich..
3 turns is prolly too much unless it's been rejetted.
 
Out is rich on the air screws. There is no standard, but 2-3 is about normal. These are intended to be a final factory adjustment, and could really be anywhere from .25-6+ turns. Adjust for highest idle then out a bit on each. Idle should drop ever so slightly when you "blip" the throttle, but should not stumble. Also, in one of the latest editions of cycle world they mentioned that it could be an issue with the choke not seating properly once you shut it off, allowing the enricher to make it run too rich. A long shot, but might as well check everything.

Make sure the vacuum port to the petcock is either connected or plugged, since you are using a test tank.

Pilot Jets should be snugly in place and should have caps over them if your carb came with them (some do, some don't) for proper function. Did you peer through each one when cleaning your carbs?? You can use a strand of copper speaker wire to clear them if they are plugged, after softening the garbage with your favorite cleaner. These are a common cause of "off-idle" issues

Airbox, airbox, airbox..... This is not like a car. You will be lucky if it runs on full choke without the airbox & filter in place.



philosopheriam said:
Folks,

Before I get flamed, I did a search, and all I am asking for is some clarification and some advice.

Before I begin, I'll make a long story short - I followed the carb cleanup series for a 1982 GS650GL with Mikuni carbs.

After reassembling the carbs, I put them on the bike WITHOUT THE AIRBOX - I now realize that this may be causing some of the following problems:

I set the "air screws" to 2.5 turns out from lightly seated. Correct me if I'm wrong, but there are no other adjustments on this carb other than the "air screw" ???

Question 1:
Does the "air screw" increase air or increase fuel as it is turned counterclockwise?

Question 2:
The bike started just fine, however, when I snap the throttle multiple times it starts to bog - could this be caused by me not having the airbox on and not enough vacuum being pulled to open the slides properly?

Question 3:
I screwed in the pilot jets until the were snug in the carb body - these don't have an adjustment, do they?

Question 4:
How many turns total do people usually have their "air screws" the bike seems to be running pig rich at 2.5 turns (granted, this is with the airbox off)

Please help, as I'd like to have this bike done already!

~philosopheriam



I'm using a test fuel tank, fyi
Click to expand...
 
Yes, I cleaned the carbs with a complete disassembly, removed all the jets, soaked the carbs, used fine wire to clean all the jet orifices, etc...

The carbs were squeaky clean when done. All the jets were unplugged. Al the jets are stock.

I will put the air screws at x2 turns before I reassemble everything.

I got concerned because the engine was pouring smoke, but as I said, I sprayed a crapload of wd40 into the cylinders after the failed petcock incident - I also changed the oil.

Also, how much blowby do you guys usually see from the crankcase vent?
 
Sounds like you pretty much got it covered as for the carbs being clean.
Dont forget that airbox, and a new set of plugs just to be sure.

I cant say I have ever noticed any blowby.
 
Plugs are new...

I set the air screws to x2 turns and I will reinstall the airbox and carbs tomorrow.

I will report my findings - the bike started like a champ and revs up fine if you go slow. However, without the airbox, it bogs on a repetitive snap.

Thanks dudes!
 
If you want a quick check without installing the airbox, fold a shop rag in half, drape it over the carb intakes. Use hose clamps or zip-ties to hold the rag to the outer carbs, while keeping it taut over the innner carbs. That will be good enough for a ride around the block, but not for any kind of jetting checks.

As others have mentioned, the pilot air jet (the one in the carb intake throat) and the pilot fuel jet (the one in the bottom of the bowl, with the rubber plug over it) both get installed snuggly. As you are thinking, the only adjustment is the "idle mixture adjustment screw" (not "air screw"). Although it might end up near two turns out by the time you are done with your fine-tuning, I like to start with them out three full turns. It makes the overall mix just a bit richer, making the bike that much easier to start when cold, but not so rich that it will foul the plugs in the few minutes you will be doing this.

Starting at three turns out, you will not likely hear any increase in engine speed when you turn the screws out (making the mixture richer), so listen for a slight drop in speed when you turn the screws in, then back out about 1/4 turn. After doing them all, check your carb sync with vacuum gauges and re-check the mixture, just to be sure.

.
 
CV carbs are wonderful but there cannot be any air leaks. Even a loose clamp on the intake side will cause problems. Tighten the clamps as far as you can.

Synchronizing is not optional. It must be done before air screws are adjusted. Otherwise some are on the idle circuit and one or more carbs are into the slow speed jet. You cannot bench sync correctly, they must be calibrated on a running bike. I didn't see where you synced the carbs so hence my finger wagging.
 
Well, success folks...!

I reinstalled the carbs, plenum, airbox, etc... I set the air screws at x2 turns out.

Started the bike up, let her warm up, and then did some off-idle tests...

Bike revved like a champ - final setting for all the air screws was 1.5 turns out. This was the only setting where I could rev the snot out of the bike, snap the throttle closed, and only see a slight dip in the revs. Leaner than this made the bike die.

Also the smoke went away, as well - must have been residual WD40 in the cylinders and the previous rich condition.

I do need to sync the carbs - time to buy a carb tune/FI sync tool :-)
 
philosopheriam said:
Well, success folks...!

I reinstalled the carbs, plenum, airbox, etc... I set the air screws at x2 turns out.

Started the bike up, let her warm up, and then did some off-idle tests...

Bike revved like a champ - final setting for all the air screws was 1.5 turns out. This was the only setting where I could rev the snot out of the bike, snap the throttle closed, and only see a slight dip in the revs. Leaner than this made the bike die.

Also the smoke went away, as well - must have been residual WD40 in the cylinders and the previous rich condition.

I do need to sync the carbs - time to buy a carb tune/FI sync tool :-)
Click to expand...
Thanks for update- it's a good reminder that if you put in the effort, you get the desired results.
 
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