carbs flood as soon as petcocks are open...help!

[sailorsam]

just upgraded to electronic ignition. Timing is right. Was running fine on points ignition.Bike had been sitting for about 5 yrs. engine and carbs were rebuilt at that time and bike ran good.Floats are @ 24mm and are not clogged. no other adjustments were made. I don't know why all of a sudden the bike is flooding.
specs : 77 engine, new dual high output coil, Mike's XS electronic ignition with e-advance(Pamco).
Battery @ 13.5 v. new plugs and wires. good spark. Please help.

 

[5twins]

If you mean fuel is overflowing and coming out of the carbs, that usually indicates a float needle is stuck open or jammed open by a piece of dirt of something. You'll probably need to remove the float bowls and clean it out.

 

[sailorsam]

If you mean fuel is overflowing and coming out of the carbs, that usually indicates a float needle is stuck open or jammed open by a piece of dirt of something. You'll probably need to remove the float bowls and clean it out.

I've already gone through the floats. everything is clear and working properly.

 

[thuban]

...and the best way to protect those carbs is using fuel line filters!

( But Thu, I use clean gas! You mean from that can you pulled the stopper rag out of? )

 

[650Skull]

I've already gone through the floats. everything is clear and working properly.

 

[gggGary]

I've already gone through the floats. everything is clear and working properly.

Um no it's not.
remove float bowl drains. put a catch can under them open the petcocks and flow some fuel, inspect the catch can for dirt/rust/fuel line slivers.
Cut something similar to this, works well.

Do a HOT water float dip test look for bubbles.

 

[Jan_P]

If the bike has been sitting a while ..it is ( or can be ) like Mr 5T says
# 2
It is uncommon to be both sides ..but It happens on one for me .I tap on the outside with a Screwdriver handle or wooden hammer handle
It has happened out on the road once also ..The girl passenger was not impressed .seeing the petrol flowing.
But I have never taken down the Bowls for it .It opens up after a while if one has nerves riding a while.
Assuming you don't have the vaccum operated Petcock .
I would close the petcock and get movement floats flexing and then open .filling up bowls again
It works for me.
I get them going but it depends on how much dirt or sticking there.Is

 

[grizld1]

You might want to inspect the fuel level with a sight tube to verify that things are in fact "working properly."

If by "flooding" you mean carbs are puking fuel from the vent lines, then something is not in fact working properly. In addition to common problems with the float and float valve, the brass float chamber vent tube sometimes (very rarely) leaks at the base. I've seen repairs attempted, but haven't seen one succeed. You might get lucky with a fuel resistant epoxy or a sweat seal with solder, but the only sure fix I know is to replace the float bowl.

 

[sailorsam]

So the issue seems to have cleared itself, bike's runnin great, no flooding. Don't know what did it. I tried the petcock off, remove floatbowl plug, open petcock and got nothing but clean fuel on either carb. Thanks for the suggestions. You guys are truly "Guru's".

 

[5twins]

Sounds like you managed to flush it clean, dislodging the dirt or grit that was stuck in the float needle seat, when you removed the drain plugs and allowed the fuel to "free flow". Years ago we found one tiny grain of sand lodged in a buddy's float needle seat. Being light brown or tan, it wasn't easy to even see it. If you had something like that, you could of easily missed seeing it in the fuel you drained.

 

[Kevin Werner]

As an aside to this obvious float problem I have had a plastic float sink. An early Honda CVCC motor had a plastic float. After chasing the problem of only running full throttle, try that with a manual andcity driving. I discovered the float seemed to be half full of a clear liquid. Ethanol. Gasoline is a 7 and 8 (heptane/octane) carbon chain, C7H14 or C8H16. Ethanol is C2H5OH. The smaller ethanol seeped through the plastic.