Float Height Help

Yes Another float height question.

750 seca 1982
Background: Bought bike last fall, rode it a little, it had no low end power, than power would surge as soon as I hit about 4 grand.

Cleaned the carbs this winter. Found that the dry heights of the floats were way out of spec. (Dont remember which way) and tiny hole for enrichment circuit was clogged in the bowl.

Adjusted floats to 17.5 dry.

Installed carbs and test drove (without sync because it hasnt come in the mail yet) and the bike rode pretty much the same with minimal power below 4 K. Then a couple days later the bike was un-ridable.

So here is the meat of my story.
My wet float height check showed the level well below the 3 mm spec. About 11mm below where the bowl mates with the carb body (at the head of the screw).

So I removed the carbs and readjusted the floats to 16.5 dry. Now on one of the carbs the float height is about 8 mm below where the bowl meets the carb body. I only tested one because gas started spilling out onto my garage floor from one of the carbs, I think the float needle didn't seat for some reason.


Has anyone else had issues with the dry height being considerably off?

 

I had trouble with my Mikunis. I just ditched the dry height adjustment, and set up a ghetto stand on a folding table in my driveway. I hooked up my tank, and adjusted each bowl by checking wet with a clear tube. Last time I did it, it took me about 30 minutes. Kind of a hassle, but I got the carbs spot on.

 

That does sound like a hassle and one I must go through. Did you use gas? Or some other liquid for testing.


*Note* reading through the service manual last night it states that the bike must be started and run to ensure float levels are correct. I noticed no one does this and things turn out fine. But that could add considerable time to setting these floats. Why do you suppose it states this?

 

What I learned about setting my floats: the 17.5mm dry height was dead on for my original needle and seat. However, the first time I checked them with fuel, I didn't hold the clear tube correctly and almost tore them back apart. I diverted my attention to something else and came back and checked them a second time. Here's the key; when you hold the tube next to the carb center-line, make absolute certainty that the tube is vertical and not a gradual incline from the elbow. In other words, tube must make a right angle from bottom of bowl straight up. If you don't do this, the level will appear low which, could cause you to adjust the level too high. Good luck!

 

I used gas. You do need to be careful about how you hold the tube. The fuel level will be at the same place, no matter how you hold it, but it is harder to "eyeball" the level unless the tube is vertical to the carb bowl.

For some reason I've never been able to get the dry height adjustment to work. Might be the type of carbs I use. I also have a hard time doing it while the carbs are mounted in the bike. In my MaximX, there just isn't all that much room to stick my hand in there once the carbs are mounted.

Anyway, if you have the carbs off anyway, it isn't a whole lot harder to set it up for a wet test. I just put my gas tank on a cinder block on the table, and set up my carbs so that they are stable and level, and then go to it.

 

Ok, one of carbs keeps taking on fuel and wont shut off.

When its dry I do a blow test and it seems to work fine. I lift the floats and air blows by and I let the floats sit with gravity and I can't blow any air by.

But whenever I add fuel to the mix it doesn't shut off and fuel pours out the carb body.

So I tried switching the float valve needles and that didnt help.

I also made sure the float floats, and it does.

Help?

 

Tap on the bowl gently with a screw driver handle or such, it will help the needle seat into where it wants/needs to be.

 

That didn't work.

 

Here ya go, give this a try: Remove the pin that holds the float to the pillar and chuck the pin in a Dremel tool. Polish the pin using some 1000-1200 grit Emory cloth, making sure the pin is smooth as glass. Next, carefully clean the inside surface of the float where the pin fits in with some carb cleaner (don't hose down the float body). Roll up a piece of that 1200 grit cloth used previously in the Dremel tool and carefully polish the inside of the seat where the needle slides. Don't go nuts here, just remove the oxide. Lastly, carefully smooth the vertical contact areas of the needle with the same 1200 grit cloth (if you have original needles, don't do anything to the rubber tip). If any one of the 4 contact areas (needle, seat, pin & float) hangs up, you can experience what you describe. Good luck!

 

I have also used the "golf tee trick"
Take a broken golf tee and chuck it in a drill. (wood one please)
Gently and slowly try to use the chuck as a drill bit in the seat where the needle valve goes. The wood will polish up the brass and take out any burrs that might be hanging out in there and will also alter the angle of the seat ever so slightly so you will be sealing on a different spot on the tip of the needle valve.

Also, I have tested them WITH GAS (not recommended)
Take the bowl off the carb while you still have gas flowing into the carb. You should easily be able to gently lift the float and close the needle valve stopping the flow.
Recommended to use good nitrile gloves or the wife wont let you in the house and put something on the floor to catch the spillage. (no SMOKING!!)

I even found a perfect size glass bowl and that's how I set my floats.
Take the metal bowl off, hold the glass bowl under the carb and let her fill up and watch the float do its job and you know exactly what is going on in there.
It's good to have a nice little valve on the fuel line but a vise-grip makes a nice pinch-valve too.

Floor protection: I bought one of those washing machine safety pan at home depot to catch my spills and all the other messes I make.

 

ok thanks for the tips everyone.

Looks like I have my work cut out for me.

I'll let you know how it turns out.

 

I just dont get it.

Set up my carbs on a stand to check them out and the everything worked this time. Took the time and followed everyones suggestions. Tested it again 3 times and not once did it over flow.

Put them on the bike and spillage. Fuel running out of that same carb all over the garage floor.

 

take the float off the carb in question and set it in a container of gas....
Does it float? :wink:
hold it under, do bubbles come out?
You can see where I'm going here...
Maybe there's a hole in the float

 

are you sure its not coming from around the fuel tubes that run from carb to carb?
If the test can your using when testing them on the bench doesn't have the same amount of fuel init as your tank there's going to be more fuel presure when putting the carbs on the bike. i think... sounds good anyway :lol:

 

Did you have the carbs level or are the pitched forward (as they sit on the bike)
If you are on the edge of overflow when level, and then tip them forward a bit you might overflow.

Are you on the centerstand or kickstand? (again the bike is not level)

 

Im on the center stand with the front wheel raised so the rear wheel touches the ground.

Its just 1 of the 4 carb body's.

 

It comes out of the air intake port of the carb so I know its not from the fuel tubes. This time I had a clear tube hooked up and watched. It filled up very fast, much faster than when I do my bench testing. So there could be more fuel pressure from my fuel tank than the bench setup somehow.

I'm going to check the float floatiness in some gas. I checked it in water earlier and it performed normal. But maybe gas has a different buoyancy than water?

 

gas is less dense than water - so it's possible that it floats in water but not gas. although, my bet is that it will float in gas, too.

 

just an update

Was going to remove the carbs and test the float in gas but decided to check it again on the bike first and it worked. Weird.

Now the bike will barely idle and the exhaust pops during idle and acceleration. Idle is hunting to. I sprayed some insta start around the carbs to check for air leaks and found none. What causes exhaust pops during idle and acceleration?

 

floats float in gas just fine. They all float the same.

Just have to ease the fuel in when I first prime empty carbs i guess.

 

probably have to synch the carbs now that you have the levels set. The miss firing/ pops would most likely be from running to rich or lean on the plugs.
Get a synch tool and set teh mixture screws. The PO likes to mess with those when they get crap in the carbs cause its the easiest thing to get to and seems to make the problem change.

 

When you checked float height did you make sure that both plastic floats were the same height? Sometimes the float assembly can get a slight twist in it by all the handling and that can cause a binding effect on the float axle making it drag or stick when on the bike.