Intermittent overflow

[Big T]

I've been chasing an overflow issue on my 78 1000

A carb will suddenly overflow for 1-2 seconds, sometimes it's #2, sometimes #4,etc.

When they're not pissing, they'll slowly drip

I pull and dismantle the offending carb, say #2, find nothing, spray all the parts, reassemble and #4 will start overflowing ( or some other)

It will be fine for a while, then start the cycle again

I've tested the floats, polished the needles and seats, triple checked float heights, cleaned and flushed the fuel tank, swapped needles, don't know what else to check

Could it be

Debris in the tank? I never find any in the float bowl
The springs on the float needles failing? I check that they move freely, could they just be worn out after 47 years?
Any ideas?

 

[Nessism]

Sounds like your fuel level is high. Right on the ragged edge of overflowing.

Why, is the next question. Float valves wear, and don't seal perfectly. Needle springs get weak. Floats age, and get heavy.

Start with performing the "clear tube" fuel level test. Adjust the float height, to the extent it helps. I've had carbs where no amount of float height adjustment changes the fuel level. This is when you start pulling out hair.

If you can't adjust out the high fuel level, my default is to install new float valves, then go from there. I have a pile of china floats, but can't say they have helped the situation much.

 

[Sandy]

Did check that they're not binding on the float bowl? Give carbs a shake after installing the bowl and you should have a nice crisp rattle from the floats.

 

[chuck hahn]

I would check the float arent canted and rubbing on the gaskets and that the overflow tube isnt cracked at the seam. Put a line on the overflow nipple and fill the bowl with water. Put finger over the tube and blow in the line and if theres any crack youll see bubbles. Polish clean and flux and solder the tubes.
I have a bunch of VM26 bowls and floats if you need any

 

[Big T]

I did weight the floats at one point and they were all within .1 of a gram. I can't remember what that weight was

Thanks for your offer, Chuck. I have enough VM parts to build 3-4 sets. I tested the float bowls overflows and they're good

 

[Big T]

I tore the carbs down yesterday, double checked everything, and reinstalled them.
#1 puked gas with 10 seconds of turning to Prime
Ordered new needles from Z1 today

 

[chuck hahn]

Put a Qtip in a drill and some carb spray and scrub the snot out of the float seat and i am assuming the sealing washer on the float seat is there and not cracked.

 

[Nessism]

Please don't try to just install needles into the old seats. They wear together as a pair. And don't get K&L, the spring is too weak to hold up the float.

You can make a clear tube fuel level tool by taking a piece of cheap nylon or tygon tubing, and using your grinder to pencil point one end. Then screw the tube into the drain screw hole as tight as you can. It may drip a little, but it will work fine to check fuel level. And speaking of that, if there are any bubbles in the clear tube that will upset the measurement. Flick the tube to drive out the air bubbles.

 

[rphillips]

Had a leaking problem, like yours, on a GS1100 I'd just bought. After having the carbs off appx. 3 times, finally found "O" ring on seat was leaking... Just a thought.

 

[Big T]

Put a Qtip in a drill and some carb spray and scrub the snot out of the float seat and i am assuming the sealing washer on the float seat is there and not cracked.

I polish with Wizards metal polish, Q tip and a drill
Also polished the needles lightly, just in case

 

[Big T]

Had a leaking problem, like yours, on a GS1100 I'd just bought. After having the carbs off appx. 3 times, finally found "O" ring on seat was leaking... Just a thought.

Wrong carbs
VMs don't have that O ring

 

[Big T]

Please don't try to just install needles into the old seats. They wear together as a pair. And don't get K&L, the spring is too weak to hold up the float.

You can make a clear tube fuel level tool by taking a piece of cheap nylon or tygon tubing, and using your grinder to pencil point one end. Then screw the tube into the drain screw hole as tight as you can. It may drip a little, but it will work fine to check fuel level. And speaking of that, if there are any bubbles in the clear tube that will upset the measurement. Flick the tube to drive out the air bubbles.

Crap, I ordered a set from Z1, they might be K&L

 

[salty_monk]

Yeah there is something better... I had them in the 1100 & they worked great. Very similar problem to you in fact. Was recommended on here somewhere. Cheaper than OEM & available. I will try to figure out what they were!