Just got my manual, and after looking at that and consulting my carb, it appears mine may have been a factory replacement or something at one time. The main air jet is located under the choke hole on this carb, and the normal location is now plugged, hence the 3rd hole. So it appears Randy was correct in assuming plugging this hole will richen the mixture, by stopping the air flow to the main fuel jet. Looks like it is just way lean. I'll try relocating the clip on the needle jet, and if that doesnt do it, I'm off to find a 1/16 drill bit and bore out my spare jet. I'll keep everyone posted, but hopefully I can ride tonight.

 

If you only knew how long I've spent monkeying with carbs.....

Anyway, here we have the 2 different styles of needle-jets:




The airjet you're talking about jets air into hole that is on the rightmost needle-jet. On the other needle-jet, there is no provision for an airjet to do anything. The rightmost jet is a 2-stroke or low-vacuum engine jet while the other is a high-vacuum or 4-stroke jet.

 

Another thought... Normally the gas level covers most of those little holes in the needle-jet, but if your float level is too low, that would uncover more holes and allow more air from the airjet to get into the mix. Since you have the manual now, should probably set the float as it states. Although, in practice, I haven't noticed much of a difference by changing the float level.

 

Hmm that is interesting. My needle jet looks basicly like the one on the left. It appears to me the top most hole does the same thing the book says the plugged bottom hole should do, its just located higher. You can see where it was drilled into the same channel though. The fact that plugging this hole makes it run perfect bothers me though. The book says it needs that hole to mix air in with the fuel, which to me means it shouldnt run with it plugged, as it would just be getting a pure-fuel charge! I did set the float, no difference. I wish 86qscamo's picture had loaded right. I just need to know how many holes there are and what is plugged. Can someone verify?

Oh and it turns out Solex VW main jets are the same thing and I have a bunch of those I'm up to a 127.5 with the clip all the way down, and it runs better with choke on, but once you shut that choke all the way, it dies right out. Plug that hole and you're in business. I find it extremely hard to believe that engine needs that much fuel, unless it has one hell of a cam in it or something!

 

Mikuni airjets go all the way down to 0.0 in size, so its not unimaginable to think the hole should be plugged. It wouldn't be pure fuel charge either because there is air coming around the slide.

Maybe you need a richer needle? Try putting washers under the needle clip to raise the needle yet further. If you don't have washers small enough, make them out of a sheet of plastic, cardboard, or something. Maybe even wrapping wire around it. Anything to raise the needle some more.

You can also put the needle in a drill and hold sandpaper to it to make the needle smaller and let a bit more gas in. But be careful, you have to sand the needle in the right spots. Next thing you'll know you're sitting there for hours n days with a micrometer, sharpie, and a stack of notes.

 

Man, I never thought tuning the stock carb could be so difficult. Are you absolutely sure there is nothing else wrong?

Another thing... In 1989 suzuki put a smaller mainjet and a richer needle in the 250S (which is basically a slightly larger version of the 230S). The new needle is the same as the 5L1.

 

I'm sick of screwing with it. Here's what I'm going to do. It wants to run with that hole plugged? Let it. It is acting like a vacuum leak through the hole. I'm going to solder the hole closed (can drill it back out if necessary), insert the 115 jet, and re-set the needle back to the middle. Then I'll re-connect the air-box, and go from there.

 

You did have the airbox on all this time right? It won't run without it.

 

I've had to make so many damn changes to this thing I've just been running it without the airbox elbow hooked up. It runs good now with the hole plugged, except the idle is super high and adjustment screw does nothing. Even adjusting the air screw in the side increases RPM the farther in you go? Plug still black as well. I'm about ready to start sourcing a new carb.

 

Most guys take the airbox lid off and have to jet up a couple jets.... You've taken the whole airbox off and are wondering why its lean???? And not only that, if you want to run with no airbox, you need a velocity stack to organize the air going into the carb. You can't run a carb without anything attached to the back of it.

Put the bigger of the 2 mikuni jets in it, put the clip on the middle or richer spot on the needle, put the airbox on with a decent filter and put the lid on nice n tight and then tell me how it runs. The filter and airbox will cause carb vacuum to go thru the roof and suck out plenty of gas. Once you get it running, then you can figure out how to run it with the lid off the airbox for more power.