Carb Confusion

[Guest]

I have a few questions I haven't found answers too yet. I have been reading on carb settings and synching.

First question, I keep getting confused on what the pilot jet and other jets are. I opened up the carbs and took pictures so that I could get some clarification on what the jets are. Also, I keep seeing people turning out their pilot screws and other scews. So if someone could identify the screw and then let me know where they should be to start with. I have a stock 1983 GS650g and would like to know the starting point for these screws? For clarification, it has the stock air box and restrictive muffler. Thanks

I have the mixture screws out two turns based on another thread I read.





Question on bench synching, when I put a paper clip or wd40 wand in carb #3's butter fly valve, I am matching this gap to the gap of the other carbs? Never seen this explained in other threads. Thanks again.

[chef1366]

That is the pilot air jet. It controls the pull of the fuel for the pilot circuit and the A/F mixture.
Air is drawn into that jet and fuel is sucked from the main jet from the fuel bowl. Since the needle it blocking the main jet it is diverted into the pilot jet and the mixture travels through the idle mixture screw where the amount is controlled with the screw. The idle mixture screw doesn't control the A/F but just the amount of the mixture that is already set with the pilot air jet and the size of the pilot jet.
Hope this helps

[waterman]

That is an air jet. Off the top of my head I think it is a 160.

[waterman]

Chef beat me to it. Likewise, in your top picture, you are correct, it is the pilot jet that goes in that hole. You should have a rubber plug that seal the hole.

[Mop Bucket]

So I was right on the pilot and the one that isn't label is the air jet? What about how far in the pilot jet is screwed in, all the way? Same with the air jet?

[MisterCinders]

Basscliff has the specs on his site. They will say how many turns for a base setting.

[SqDancerLynn1]

Yes they should all be hand tight. The only adjustment is on the top of the carb on the intake side about two turns is close

[Mop Bucket]

What about the bench synching the carbs. Am I making the gaps the same? Say I have two paper clips, one to hold open carb #3 and the other to make sure they all are the same?

[Steve]

Don't bother with mechanical stuff in your carb throats to do a bench sync.

Just adjust #3 with the master idle screw until there is a sliver of light showing past the butterfly. Adjust the others to match.

Here is what you are looking for:


Unless you have that paper clip or WD-40 tube exactly in the same place on every throat, your measurements will not be the same. Much easier to eyeball a sliver of light. The smaller the sliver, the easier it is to match another one. Then, turn the master idle adjustment to open them, watch to see they all open at the same time.



The main jet, the pilot fuel jet (the one next to the main jet) and the pilot air jet (the one in your second picture) should all be reasonably snug, so they won't come loose on their own. Don't forget the rubber plug over the pilot fuel jet, the bike won't run right without it.

The "idle mixture adjustment screw", which many mistakenly call "air screw" is the one that you should turn out between two and three full turns from lightly seated.

Here is that screw:


Hope this helps, thanks for asking.

.

[tom203]

Make sure those carb pistons slide up and down real easy and there are no minute tears in the diaphragms.