carb screws for adjustment

[vyvyan]

hello all,

i have been looking at the forums for some time now and its been good and helpful!

i have a GSX750ES (1989, sorry! :shock: ) and i have had fuel problems, sounding like it was running on 3 not 4.
As it had been stood for a while prior to my purchase, being lied to by several garages cos im a girl and they weren't prepared to look at an 'old' bike and it running rough after a fill up of petrol in cold weather and started peeing fuel from the overflow of carbs 3 + 4. i figured it was a carb problem! i looked on here cos my carbs seem to be mikuni BS32's.

i took it apart and did a clean (ive learnt since not a good enough one!) i've put it back on the bike (as the landlord didn't appreciate it on display in my room). the tank sounded as tho its got rust in it so ive put an inline filter in at present rather than a tank lining job. i didnt do anything to the fuel tap and i replaced the spark plugs as the previous ones were proper black. the fuel tap works ok.

ive got fuel in the float bowl of 1, 3 and 4 and no wetting of any plug. i know i will have to take it off and clean it more thoroughly but im not sure of what screws to turn for what in terms of fuel and air once i come to putting it back in the bike.

my manual says 'pilot jet' - 2 1/4 turns back and no other reference to turning screws for mixtures and the like.

ive looked on the cleaning series PDF on this site and it refers to the
1) air jet on the front of the carb (air side)
2) air screws on the top of the carb
3) pilot jet in the underside of the carb

which one is my manual referring to and is there more adjusting screws for a specific number of turns than the 'pilot jet'?

im no mechanic but me and the haynes manuals are getting to know each other quite well! i got fed up of not knowing how to fix it, so i read up on it as best i could to try and fix it myself.

sorry to waffle and thanx for any input! [-o<
Em n Vyv

[chiphead]

Welcome to the forums.
I'll leave your question to folks more familiar with what you have...but...start by setting the pilot "fuel adjustment" screws to 2 turns out from a light bottom. I think those are the only adjustment screws you have on your carbs, unless things are different over the pond.

[Dave8338]

Greetings. There is no adjustment for the pilot jet. It is a sized jet that can be changed, but has no adjustment. The air jet (carb intake side) is also a fixed jet, no adjustment except for size. Your air screws (if not capped) can be adjusted and should be set to 1 1/2 turns out from lightly seated, as a starting point. They are at the front of carbs, next to the inlet rubbers...if they are capped, the caps can be removed. Your pilot jets inside the carbs should have the rubber plugs in them, when these get old, they can shrink up and fall out to the bottom of the bowl and render the jet near useless. The inline filter in my opinion, is not a great idea as they have a tendency to limit the fuel flow, however, this can be debated. If there is no fuel in the number two bowl, you'll neet to pin that issue down, it may be a stuck needle/seat combo or plugged passage. You have some work ahead of you, but this site will make it next to painless. Keep us posted.

[MidnightRider]

You're correct in learning while you fix the bike, as you've found out you need to find someone you can trust and that's really hard unless you know a little about the problems. The carbs probably need a thourgh cleaning. The carbs overflowing probably have a float problem. Probably just dirt or old gummed up fuel. You do need a filter in line until you get the tank cleaned out because pieces of rust will just keep going into the carbs. However, the filter isn't in front of the fuel petcock so that is getting a lot of debree in it when there is fuel flowing.
Back to the floats, they need to be adjusted after you make sure the needle valves move freely under the float tabs. Useing your manual you can adjust these to the correct level with the carbs upside down. If the float valves move freely and you adjusted the floats properly you shouldn't get an overflow when they are back on the bike. After adjusted, I usually put a fitting where the bowl drain screw goes and connect a transparent tube to it, then put it up along side the carb. This shows you where the fuel level actually is while the bike is running. Some manuals describe both metholds.
I think there is a section on this site describing how to clean the carbs.

[KEITH KRAUSE]

Your mixture screw at the top is your only adjustable jetting component per carb.
1 1/2 to 2 turns out is a good starting point. These screws should be adjusted using the highest rpm method. If adjustment is difficult or you notice no rpm change, that suggests something else is wrong with the carbs.
The carbs must be completely clean, as you've mentioned. Otherwise, a cylinder can starve for fuel and not fire correctly. You didn't mention any fuel in the #2 bowl. You did mention it seems to be running on 3 cylinders.
Rust will be a constant headache, fuel filter or not. I really suggest you clean/seal the tank. Less trouble in the long run.
If you had black plugs, and assuming the air filter is clean, that suggests a weak spark and/or additional carb problems such as, incorrect jets, poor float level adjustments, worn/missing o-rings, etc.
If you take the carbs apart again, please verify what main, pilot, and air jets you have, as well as jet needle position (any evidence of shimming?) and float levels.
As for spark, verify the plugs are the correct heat range/gapped correctly and the spark is a good bluish/white. Be sure the plug leads are in good condition and not cracked/arcing to ground somewhere. Use a new plug to test read. If the spark is orange/weak, you have electrical problems that may be the cause of the black plugs.