Air screw adjustment??

[se3388]

I am rebuilding the carbs on my GS550E and was wondering what to set the air screw(on the top front of carb that has to have the plug drilled out to take out the screw) to. I believe the screw was 1.5 revolutions off of being seated. When I install the little aluminum plug do I need to put some adhesive on it or just tap it in lightly? Manual hasn't made it here yet so I'll ask question. Thanks for any info.

[dickidav]

hello and welcome, on my gs450 i started the screws at 2.5 to 3 turns from lightly seated. then adjust from there. you don't have to put in the plug if you don't want to, but if you do push it in and if it seats well thats all. you might use plugs like on the pilot jet also. dave

[renobruce]

If the bike ran good before, set them where they were. And you don't need to put the cap back...you will want to be able to adjust the screw if needed.

Once the bike is running, do a plug chop test at minimum throttle and read your plugs. Turning the screw out richens the mixture, in leans it out.

[se3388]

Unfortunately I don't know how it was running before I got it as it didn't even have any carbs on it when I got it. There were 2 sets in a big box, it had been setting for about 2 years like that.
At the risk of sounding dumb what is a plug chop test. I know that you can look at the color of the plugs but haven't heard of the plug chop test.

Steve E.........

[renobruce]

Unfortunately I don't know how it was running before I got it as it didn't even have any carbs on it when I got it. There were 2 sets in a big box, it had been setting for about 2 years like that.
At the risk of sounding dumb what is a plug chop test. I know that you can look at the color of the plugs but haven't heard of the plug chop test.

Steve E.........

If the bike is stock (stock air box, stock pipe, stock jetting) I would set them at 2.5 turns out as a starting point.

A plug chop is a method of checking your different circuits on the carbs...pilot, jet needle, and main jet. Each is checked at minimum throttle, half throttle, and wide open throttle, respectively. To check your pilot, cruise down a flat road at minimum throttle (maybe 5th gear, 45 mph) for about a mile. Shut the throttle off while pulling in the clutch and hitting your kill button. Pull over at a safe place, then pull each plug and check the color. Adjust your pilot screws based on what you see. You want a light to medium tan color. White is too lean, and black too rich. Make sure you check each plug as there can be slight differences in each carb's needed setting. If you need to adjust, don't turn the screw more than 1/4 turn. A small adjustment can make a big difference.

[KEITH KRAUSE]

Are these CV carbs? Set them initially to 1 1/2 out. Warm up bike fully. Adjust them using the highest rpm method. Adjust the idle with the idle knob to factory recommended rpm. Slowly turn a mixture screw until the rpm's peak. Stop. Reset idle to factory recommendation with the idle knob. Repeat until all four are set.

[se3388]

Well here's how it is so far, I set the air screws all at apprx 1.5 turns from lightly seated. When I try to start the motor it will hit for just a second then just turn over till I let it set for at least 30 minutes then it will hit once again when I try it. That is with the throttle at idle, it won't do it if I give any throttle. It has gas in all the carbs and I pulled the plugs to check for flooding but the plugs were all dry. Any ideas?
Yes Mr Krause they are vacuum, Mikuni type.


Steve E...........

[KEITH KRAUSE]

Cold starts require a decent amount of choke to get going. You don't mention any choking.
What was done in the carb rebuild? How much did you disassemble them?
Poor starting could also be the idle knob isn't adjusted far enough. The carbs could also need (at least for starting purposes) a bench synch. Also, be sure the carbs are properly re-fitted into the intake manifolds and the air box boots.
What year bike?

[se3388]

Choke was tried 1/4th, 1/2, 3/4th and full on with no change. The carbs were stripped and dipped. All jets in each carbs were changed as well as new air screws and springs, needles and seats.

Steve E.........

[Nessism]

Something doesn't sound right - the plugs should be wet if you crank on the engine with full choke. If the airbox is not installed though the bike will run like crap so put it back on if that's the case.

Regarding the pilot screw adjustment, my old 550 didn't run right until the screws were set at 3.5 turns. I'd use at least 2.5 turns for a starting position.

[KEITH KRAUSE]

Again, what year is the bike? If you had 2 sets of carbs in a box, how can we know if the set you installed is the correct one (if either set is correct)? And why were the jets changed? When necessary to replace jets, they should be genuine Mikuni jets. Are they? Did you bench synch?
Lots of unknowns here. Describe what you've done and how you determined which carbs to use and why you changed jets.

[se3388]

It's a 1980 GS550E, I did bench sync, as best as I could. Both sets carbs were identical down to the size of jets (92.5) and they were both identical to the ones on a GS550 I compared them to (externally). The carb kits were for the GS550E with Mikuni carbs, at least that is what it said on their labels. LOL. I set the air screws at 1.5 out. They were the same size jets that were in the carbs to begin with (92.5). I even set the float height according to the manual. The boots on the head seemed pliable and not hardened, clamps were good as well as the boots to the airbox, it and the filter is in place. I know it's probably something I have done, usually is. LOL.

Steve E.........