JDX4 special- wont keep pumping fuel

[jdsnowfire]

i have a JDX4 special that keeps geting air in the fuel line. i was able to ran it around the yard 200' or so and then it died. i can get it running if i fill the lines and carb, and dump some gas in the cylinders. it will run a couple minutes at wide open or at idle, but will not stay running longer than about 5 min. i replaced all fuel lines and the impulse line. i tried both the fuel pump that was on it and a barely used mikuni from shade tree. i am running about 40/1 gas/oil mix. every time the engine dies there is air in the fuel line leading from the pump to the carb- air bubble bout 2-3" long.

any ideas on where to start looking?
crank seals?
fuel pump bad?
air leak or bad check valve?

[400brian]

Have you pulled the fitting at the tank out and looked at the pickup line, screen and check ball fitting? Clamps on all the line connections?
I don't think it is ever a bad idea to replace the crank seals on a 30+ year old 2 stroke.

[jdsnowfire]

yeah, i replaced the fuel line inside the tank, the check valve appeared fine but i'm not positive. all connections have hose clamps.
so probably crank seals then?
where can i find crank seals?

[Matt]

I would replace that check valve first.

[lwb140]

got a spitfire acts kinda the same way the crankseals are leaking horribly bad, kinda think the pulse is too weak to make the fuel pump correctly .ill know more when i get seals changed i guess wade