Is it running well? Are you still stock air box and exhaust? Do you know what carbs you have? What is the plan, are you rejetting?
You can find the 91 microfiche here. My '89 1100 manual includes all years for the generation from '89 to '91 - I am hoping the 750's also were grouped the same.
This may also be helpful depending on what carb you have. Poke around on the carlsalter site for other goodies. It is safe to download from there. I have some manuals on a thumb drive somewhere, I will check it when I get home.
They did that from the factory for smoother transition, and cylinder cooling. My '95 750 was 115, and 117.5 stock. I am running 117.5 across the board now. As you SHOULD look this up to verify, my bet would be you are at 112.5, and 115 stock.
It depends on what mods have been done to the bike, as to what jets you will need to put in them. They typically left the factory a little lean for emission purposes.
Do you still have the stock airbox installed?
Do you have a stock, or K&N filter in it?
Does it have an after market exhaust, or muffler?
Do the carbs have adjustable needles?
Answer these questions for me, and I can help you get it really close. You can fine tune from there.
Ok. I have stock airbox, no mods to it , stock style air filter. Regular Yosh header with Hindle muffler. Adjusrable needles. Location L.A. Cal. Planning to leave as a daily driver. So outers would be the leaner jets?
Lower your needles one notch. If it still seems too rich from there, put 112.5's in all four carbs, and put your needles back to the 3rd notch. It's a process to get them dialed in. Sounds like you are almost there.
I would start with dropping the needle one groove (if you haven't already done that). If you are still too rich, then drop a jet size, and raise the needle back to the middle, and keep going from there. Tuning these carbs is a process. There isn't a solid answer from one bike to another.
I agree with Spyder, dropping the needles is pretty easy and quick. Drop the jet size when you run out of adjustment room with the current set up. No matter what changes you make - only make one change at a time then test. I made a couple changes at once and got so lost I had to baseline and start over.
Dropping the needle leans out the mid range. If you think you are too rich all the way at the top, then drop a jet size across all four carbs. I think you said you have 115's in there now? Drop down to 112.5's.
I went ahead and put in 112 all 4. I then tried revving it and it wouldn't rev probably over 5k. I'm guessing at rpm's because my tach don't work. I did not mess with needles ,as it used to rev normal months ago when I last messed with it. Are the mains and the pilot jet the only things that get plugged up when sitting for months?
Spyder can correct me but I suspect you are going to have to raise your needles to the 3rd notch. They are kicking in supplying fuel at about that RPM I believe. A flat spot there may mean it is not enough fuel.
You may want to make sure your emulsion tubes are not gummed up. They feed fuel to the opening governed by the needles if I understand it correctly.
Pilot jets are smallest and plug easily. If it is starting and idling they are likely clear.
So you have had these carbs out a few times, and haven't cleaned them?
Ok, we need a good base line. You are working much harder than you need to. Pull them out. take them apart. Run a guitar string through EVERY hole you can find. ESPECIALLY all the tiny holes in the emulsion tubes. When you are putting them back together, stick with the 112.5's (STOP) Are you using genuine Mikuni jet's or are you using Dynojet jet's? This is important because they are a completely different sizing index.
I bumped up to 3rd from the bottom. these are 5 position needles,btw. It seems the same really, but this time it seems to do like a "brrr" sound and stumbles then revs up poorly then backfires. Something like that. Didn't refresh page before posting this. I'm using mikuni jets.Te mains are brand new,0 miles and the pilots have been cleaned. The emulsions not.