Rough Running Mikuni

904 Views 7 Replies 5 Participants Last post by Meulen, Oct 8, 2002

skrnich

Discussion Starter · Jul 15, 2002

Does anybody out there really know their Mikuni's? My '92 GSX 1100 - G has been down for about 2 years, where the carbs got gunked up from sitting. I took the carbs out and gave them a good cleaning and set the floats 'to spec.' The bike is running very rough, where I believe it is starving for fuel. The plugs are clean. That float spec is a little goofy, with that little spring plunger at the end of the inlet needles. I've been a gear head since I was 15 (23 years), and have built a heck of a lot of carbs 'for cars,' incuding the 6-pack on my 65 Barracuda. However, this is the 1st time I've played with Mikuni's, and was wondering if I'm missing something or I need to compensate for something not pointed out in the manual. Any advise would be welcome.

Thanks,

Steve

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Y2KR1

· #2 · Jul 17, 2002

Maybe this will help...

To adjust float height:

1. Tilt the carbs so that the floats just flop over towards and into the carb body.

2. Tilt just enough to touch and close the float the float valve, but...

3. Do NOT compress the float valve spring when measuring.

4. With the metal adjustment tang on the float just touching, but not compressing the float valve spring, measure to the highest part of the float from the gasket flange. If there is a gasket or o-ring stuck to the carb body, remove it while measuring.

5. If the floats are different, right to left, use the highest float (the one farthest away from gasket surface).

6. To correct the float height setting, bend the small metal tang, then recheck the measurement. Bend the tang a little bit at a time till you get it right. Must be all within a .5mm (1/2mm) or .020" range of each other.

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skrnich

Discussion Starter · #3 · Jul 22, 2002

Thanks for taking the time to think about my dilemma. I've been travelling for work, where I just got to respond to your suggestions, today. I actually took them apart, again, last week. The spec gave +/- 1 mm from 14.5 mm, which is right where I had 'em. I just moved 'em up to 13mm, where it is now running a lot better. I've got a feeling 13.5 is right where I need to be. Now all I need is to replace my clutch discs, all brake pads, and the front fork seals, and I should be dialled in. It hasn't run for a couple of years, so I think I'm going to have to massage it for a while til I can get some good miles on it.

Thanks Again,

Steve

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Y2KR1

· #4 · Jul 24, 2002

Sounds like a plan, good luck!!:twofinger

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Meulen

· #5 · Oct 7, 2002

skrnich said:
Thanks for taking the time to think about my dilemma. I've been travelling for work, where I just got to respond to your suggestions, today. I actually took them apart, again, last week. The spec gave +/- 1 mm from 14.5 mm, which is right where I had 'em. I just moved 'em up to 13mm, where it is now running a lot better. I've got a feeling 13.5 is right where I need to be. Now all I need is to replace my clutch discs, all brake pads, and the front fork seals, and I should be dialled in. It hasn't run for a couple of years, so I think I'm going to have to massage it for a while til I can get some good miles on it.

Thanks Again,

Steve

On the old GSXR motors I had also found that adding a Pingle Petcock valves helps a ton. I really allows the gas to keep flowing even in the high end so it's not starving.

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ddub

· #6 · Oct 7, 2002

Did you remove the main jets, emulsion tubes, pilot jets, and clean them to a nice shine? has a jet kit been installed? if not you might want to remove the factory plugs that block the air/ fuel mix, that needle needs to be clean, check the small o-rings in there(air/fuel needle) , they can be reused if in good shape, are you useing a stock air box? also sync when done. There is some good info at www.factorypro.com , just wanted to help

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Odysseys

· #7 · Oct 8, 2002

did you also check the pet cock (sp?) take it out of the tank and check the filter screens and gas filter

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Meulen

· #8 · Oct 8, 2002

Hey,

change that Petcock out either way. I changed mine on my '92 750 and went from running consistant 11:60's to consistent 11:30's on the strip simply because of the reduced starvation on the top end. That was with the CV Carbs. It ran even stronger after I swapped out the CV's for the Mikuni flatslides.

BTW: for .3 gain I only remember paying around $60-$65.

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