PHM40 flooding bike has been idle for 8 years when I put fuel in both carbs flooded removed & checked needle & seats both look OK checked float height 18 mm reassembled same problem needle is vitron tip.

try screwing the bolt of the fuuel holderr in the carborator, whhichh is generally used for overflow, screw it tight ,

It sounds like your float height in carb is too low or your needle and seat are worn. Sounds like your float being low is letting in too much gas into carb bowl and subsequently overflowing out into air cleaner. Remove carb, remove bowl, and check float height. Most are adjustable by gently bending the small metal tang where needle connects to float. Also, check needle and seat, if these are worn they will not stop fuel from entering carb and overflow as well. I am certain if you check these you will find your answer. Good luck.

I’m happy to assist further over the phone at https://www.6ya.com/expert/layne_0fccff498c319c32

The needle valve has a very fine neoprene tip which especially with newer gas (they sneak a lot of alcohol in) deteriorates and leaks.
Replace the needle and seat, check your float and be sure it's not leaked(if metal, give it a shake next to your ear, listen for gas sloshing) or the float saturated (composite float, take it off put it in a jar of gasoline, if it sinks its bad).
If you really want to be sure, check the float height according to specs and adjust as necessary by bending the tang where the float and needle meet. Best of luck to you

Replace the needle and seat and ensure the seat is tight check float height and small spring is attached to the needle.

Replace all the float needles and measure the float height. Flooding is usually caused by float issues.

By "gas valve", what are you talking about? Are you talking about the fuel petcock in the tank or the "needle and seat" in the carb? You say you changed the float and the "gas valve" but did you set the float height?

Your carb has a hung float or needle and seat issues.

You have to take the carb off the bike and consider replacing the float and/or needle and seat.

You might get by just raising the float level. But this is only a stopgap maneuver. Buy a new float!

You bike is flooding so it wont run right until this is fixed.

The reason its only flooding while its running is because your bike has an automatic gas tank valve that opens when the bike starts and makes vacuum that opens the valve. It is saving you from the bike totally filling up with fuel!

You will have to adjust the float pin of tht particular carb and don't remove them off the rack..just pull them out of the engine and work on the one tht needs attention.
Hope this helps!

I had the same problem - actually more than one problem:
1) Floats in the carburetor bowl (at the bottom of the carb) are getting stuck. Remove the carb; carefully disassemble the bowl & float assembly (pay attention to gasket orientation and don't lose the needle valve that the float-tab presses on!); use a carb cleaner from AutoZone or similar, and a toothbrush to clean all the parts. If carb is not too dirty, leave the jets and mixture-adjust screws alone (otherwise will have to re-adjust later).

2) Overflow tube is plugged (hence fuel in the cylinder instead of on the ground). Clean both ends of the brass-looking tube from inside and outside the carb bowl. Make sure you can blow through it or it is still plugged. Toothbrush and carb cleaner should do the trick. Replace the short flexible tubing that connects to the overflow on the outside of the bowl - transparent polyurethane tubing is less than $1 per foot at your local ATV/motorcycle shop.

3) Air Vent tube is plugged. Same thing as the Overflow tube but mounted higher up in the carb (not in the bowl). Clean it the same way and replace the flex tubing with another short piece of polyurethane.

4) Make sure the float-tab and needle-valve move smoothly. Mine was catching and getting stuck so I carefully "polished" the face of the tab with 400-grit emery paper, and then made sure to clean the area from grit. Smooth as a hot knife through butter now.

5) Set the float level by CAREFULLY bending the tab that pushes on the needle valve. On my 1981 175MX, float height spec is 21mm when just making contact with the needle. Yours may be different though.

6) Reassemble the carb after making sure all dirt and debris are gone. Use a new bowl gasket or at least put a good gasket-sealer compound on the old gasket. Attach the short lengths of transparent polyurethane tubing to the Overflow and Air Vent. When installing the carb, the Air Vent tube should just be 2" long and point out to the side; the Overflow tube should route through the frame near the swing-arm and point down to the ground.

7) MAKE SURE the Oil Feed tube coming from the AutoLube oil pump is connected to the carb (brass-looking fitting toward the cylinder-end). I replaced mine with transparent polyurethane tubing (different size than the Air Vent and Overflow), so now I can see that oil is being presented to the carb!

8) If the carb was nasty-dirty, you may need a new air filter. Mine was disintegrating. I recommend also putting an in-line fuel filter between the petcock and the carb, again using short lengths of TRANSPARENT polyurethane tubing (so you can see that fuel is flowing). You may also need to adjust & prime the AutoLube oil pump.

I highly recommend getting a Clymer manual (check eBay) which shows all these procedures and gives you the right specs for float height, etc. based on your model / year.

Replace the needle valve.This pushes up with the float and shuts off the fuel supply.