02 Katana Low MPG (22)

[sinisterknights]

Hello everyone

I have been trying to troubleshoot low mpg problem for a little bit and figured I would come here since I am quite stumped. I was getting about 19 mpg and am currently up to 23 mpg. To preface my motorcyle sat for about a year with old gas in it.(Since cleaning the old gas out and cleaning carbs fresh gas has been in it and it has run through about 11 gallons)

So I started by completely taking apart and cleaning the carbs and setting the air/fuel screw to 2.5 turns. I changed the oil (and oil filter) in it to have the right oil and right amount (I found when changing oil the bike had way too much oil in it). Then I set my idle to factory reccommendation (1,200 rpm). My brakes are not dragging and I renewed the brake fluid. I have stock sprockets and chain on the bike (recently cleaned the chain). I also used compressed air and cleaned the air filter. I also replaced the fuel filter

The bike is a 2002 Katana with only 5500 miles on it. I did drop it a couple years ago but no issues after until it sat for a while.

I am completely stumped and cannot pinpoint the issue I am hoping you guys may be able to help please

[92xjunker]

Over full oil....did it smell of fuel? Are the carbs the stock setup?

[sinisterknights]

No I just accidently put in too much oil, it didn't have fuel in it. And yes the carbs are stock, no aftermarket exhaust either

[Kreylyn]

Stock carbs won't burn that much fuel with out them leaking. That leak may go into the oil, may only occur when running and forced out the exhaust, or may be draining out the air box... but it's leaking somewhere, somehow.

The most likely issue is a float needle not sealing, and the fuel is flooding out at least one carb. If that is only happening when the bike is running (possible if the petcock works right) then you would likely never see it, and only one cylinder getting flooded will not be real apparent in a running issue to most riders. I've seen peeps ride on 2 cylinders and never realize it.

The simple of it, you go back to cleaning and checking the carbs are properly working. Specifically, do a bench float needle seal test.

Krey

[sinisterknights]

Stock carbs won't burn that much fuel with out them leaking. That leak may go into the oil, may only occur when running and forced out the exhaust, or may be draining out the air box... but it's leaking somewhere, somehow.

The most likely issue is a float needle not sealing, and the fuel is flooding out at least one carb. If that is only happening when the bike is running (possible if the petcock works right) then you would likely never see it, and only one cylinder getting flooded will not be real apparent in a running issue to most riders. I've seen peeps ride on 2 cylinders and never realize it.

The simple of it, you go back to cleaning and checking the carbs are properly working. Specifically, do a bench float needle seal test.

Krey

So I took apart the carbs today to bench test the float needle. I pulled my spark plugs and found all were okay except cylinder 1 was running rich.

Took apart the carb and tested the float needle and it seals well. Found that the o-ring on the main jet was ripped and didn't seem to be seated right. Hopefully changing the o-ring will bring up my mpg by 20? I am hard pressed to think it will, but worth the shot. Running to the store to buy orings now