Quick float height question

I wasnt a chemistry major but wouldnt it just be easier to use gas ???? I dont think it would be smart to put anything other than gas in a carb JMO

Could experiment with the same carb by repeating the clear tube measurement using common inexpensive household rubbing alcohol, and comparing the resulting fuel levels between alcohol and gasoline, which would demonstrate the comparative buoyancy between the two different fluids.

Don't forget to wear a genuine Marty Feldman â„¢ protective white laboratory coat.

Good Fortune!

for the Keihin CV34 carbs on a 750/4 the fuel level should be 4mm below the join between bowl and body when measured with the clear tube method.
Best way to do it is to put the bike on center stand. attache clear tube to nipple on bottom. open screw. hold tube against the body and actually measure and record the height with a ruler or similar. For the inside carbs hold the tube against the outside carbs.
Take the carbs off. turn them upside down. Take off the bowls and with same ruler measure how high the floats are.

Do the math to figure how much to adjsut each float so that the fuel level is correct. Thanks Tek9ine for this tip.

Put everything back together and rock and roll

I dont know about other bikes but on the 750/4 having the fuel level spot on is so much more noticeable than a carb synch.

Carbs are off the bike. I always heard that keeping the carbs at a level angle rather than on the bike was the most accurate way to measure your floats.


Also, for my 81 Yamaha XJ650 Maxim, I found that windshield washer fluid was almost the same specific gravity as gasoline. After measuring with the washer fluid than going to gas, it was exactly where it was with the washer fluid. Guys on the XJ forums say it has a possibility of leaving deposits, but I never witnessed this.

Just a suggestion, it is worth a try if you dont want to spend too much time around gasoline, but I do recommend double checking with gas. I will only being doing mine with gas.

ravenz07 wrote:

Carbs are off the bike. I always heard that keeping the carbs at a level angle rather than on the bike was the most accurate way to measure your floats."

and u heard right, off the bike is the most accurate

The reason I was asking for something other than gas is because I do alot of my carb rebuilding in my bedroom on a work bench I have set up. ( no garage ) and the wife tends to get a little upset when I'm pouring gas all over the place. something about smelling the bedroom up. I don't understand some girls. I was thinking rubbing alchol myself. thanks for imput guys.

makes sense, yea alcohol would work, maybe even some Stoly ...:woohoo:

I still would recommend windshield washer fluid.

It would be interesting to see results of an experiment comparing the levels obtained with the identical carb using gasoline, then windshield washer fluid, and then rubbing alcohol.

And also with some cheap whiskey (in the carbs).

Good Fortune!

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With a carb having a known correct fuel level, rubbing alcohol will result in either a slightly higher or lower observed fluid level inside the clear tube.

Assign it a scientifically appropriate name such as "correct level using alcohol," which may then be used to determine and correctly set the floats in the other carbs when using alcohol.

Good Fortune!

Got to work on the carbs today. I am thinking the PO had new floats installed but never bent the tangs. They looked pretty new. His "mechanic" said the carbs needed a synch due to the flooding. After gas came pouring out of the top of the float bowls (Yes I know, I am going to order some new ones shortly) I knew what the real problem was.

So, I pretty much only bent the tangs once and this is what I got...

Carb 1 (left carb as installed on bike)



Carb 2



Carb 3



Carb 4



From looking at the pics, I assume 2 and 3 might need adjusting. What do you guys think? Sorry if the angles are messed up, I tried my best to keep it level, but holding a fuel line and a camera is not the easiest