Carb Carb Carb

ok so i finally got everything wired right and found out that i do in fact have a Z600 w/ 49cc, everything has been good untill a few days ago...

i went outside to fire up and ride the bike for a bit and got a surprise, when i push the primer bulb to prime it, i no longer get a steady flow of fuel throught the return line, just lots of air bubble filled fuel, so i checked all the lines and theyre all good no leaks or cracks, and now when it runs it will only run with the choke on then when i hit the gas i have to shut the choke off, then choke it when i come to a stop so it will idle

i then took the carb off, cleaned it out real good, cleaned the filter, screen, and checked for leaks around the intake manifold, all was good so i replaced evrything with new gaskets put it back together and im still getting the same thing......ive got the mixture screw set at 2-1/2 turns out, ive tried richening it and leaning it out but no change

Help im stumped and getting a bit frustrated

sorry for the long post but i figured a very good description on what it was exactly doin would make it easier on everyones diagnoses on what could be wrong

thanks in advance for any help

i had the same problem and made it easy for myself and just replaced the carb....it is the problem with the seal that is between the carb body and the primer body.............

thanks since it seems there is no saving this carb i do have a chainsaw with the same carb that i could swap over

The bubbles in the return line is telling me you have bad fuel flow. But first are you pumping the primer fast or slow when pushing the primer bulb? Pump it slow and see if you can get the bubbles to stop or at least turn into small little bubbles. Heres afew things to check. Hold a flashlight under the gas tank and then look through where the gas cap goes to see if there is a bunch of crap in the tank. If that's good than while the cap is off push the primer bulb slowly and see if the bubbles in the return line stop. If it does than the vent hole in the gas cap is plugged up. Check the 4 screws that hold the plate down that holds the primer bulb in. Maybe loose and letting air in. You might take it apart and check the check valve inside the primer bulb for any cracks or tears or a piece of crap inside it.
If your going to switch the carb with the your chain saw check the bore in the carb and make sure it's 12mm to 15 mm. If it's smaller it's no good to you.

thank you for your help

the tank is clean, when i got the bike i went throught the whole thing took everything apart and put it all back together.....looked like showroom quality after i was done, it ran great for some time now untill this little bug

the tank is 100% clean i put a new filter on the pickup tube in the tank and cleaned the screen in the carb, all the gaskets are new and tight, but one thing you mentioned that i didnt know it had was a check valve in the primer bulb.....i always pump the primer at a slow and steady rate just like i would on the chainsaws.....the bubbles in the return line would tell me there is air getting in the system but i know its not from the lines or tank, the cap is brand new, and since the gaskets are new how else would any air be getting in?

is the check valve in the black block above the primer or the aluminum block above the black one? is it the circle thing that the primer seals too?

thanks again for your help

The valve in the carb is a small duckbill check valve and it is right under the primer bulb and you can see it through the primer bulb. So yes it the circle thing the primer bulb seals to. The air can be getting in if 1 of the screws is loose or if there is a crack in the black plastic piece under the primer bulb or like dragonkeep said through the seal around the primer bulb.
Sorry A couple of those thing I had you check was for air in the fuel line not the return line. Like the vent hole in the cap and the crap in the tank.

alright cool, ill check that out tomm.

and hopefully i just didnt get it to seal/seat right or something

thanks alot man ill update ya tomm. when i finish