Need help with carb flooding out saw

[rmh3481]

The problem with the High Nub diaphragm is the limited amount of travel it can achieve. When the fuel held on the metering side of the carb is consumed by the engine, the diaphragm is drawn down to the lever, and eventually the lever lifts the needle off the seat. When the lever reacts with the needle valve, fresh fuel is drawn into the metering chamber. This cycle continues over and over. Because the nub is so high on the aftermarket diaphragm, it becomes impossible to set the lever height because the engine floods.

The solution to this problem is to remove the high nub with a file. Carefully fold the diaphragm so that the nub and star weight can be held between your fingers. Using a clean sharp file, run the nub over the file and lower the nub. Its alot easier to run the diaphragm over the file than the other way around. Just dont allow the diaphragm material to touch the file or you will cut a hole in it. Take your time and good luck with the project.

 

[Joe Bopp]

First wanted to say thanks to everyone for helping me out and getting several things to try.

I have an update/closure for this issue.

1. Filed down the High Nub diaphragm. Reinstalled in the carb but still had the same issue. Saw flooding out.
2. Confirmed that running the primer bulb caused gas to flood out the pulse port
3. Focused on the fuel pump side. Opened that side up and had a brand new carb kit in hand. \
4. Confirmed that the fuel pump diaphragm was the correct one. Swapped it out from rubber to one of the brown ones in the new kit. Reassembled and carb stopped pouring fuel out the impulse port when primed.
5. Reinstalled carb but found that the saw would only fire momentarily on choke. Couldn't get it to go with stock carb settings. Since it sounded like it had now gone from flooding to starvation I went back in and adjusted the metering lever a little higher now that I had filed down the nub.
6. Reinstalled carb and was FINALLY able to get the saw to run. Dialed in the carb and cut a few pieces of wood with it.

Long story short it seems like the rubber diaphragm was just not sealing for some reason and allowing fuel to just pour into the carb. Same shape and setup. Not sure why it didn't work. Now to wait and see whether the saw restarts later today.

Curious to hear from everyone why the fuel pump diaphragm wouldn't seal. I don't think I am supposed to double stack diaphragms or anything. Replacing just that seems to have resolved my issue.

 

[pioneerguy600]

I have come across this issue with fuel running back down the impulse line on a few AM carb kits installed by others, saws brought to me due to flooding issues, I found an extra hole or opening in the pump side diaphragm, not required for the particular carb they were installed in. One needs to be very certain the new replacement diaphragm is exactly the same as the one being removed, checked hole for hole or opening in the diaphragm, one misplaced hole or opening and the carb pulse circuit and it is no longer sealed. Not saying this is the OP`s problem but it does exist with the AM carb replacement kits.