GX390 will not start


New member
Old thread is gone

Tried it all on this thing

Just got carb back from EC and it checked out

Carb won't pump gas unless choked by hand

Billet rod
1.3 rockers
55lb springs
Port and polish
40/35mm valve job
Chromoly push rods
Mikuni SBN 38mm
Parsons Valve cover
Billet flywheel and 4 degree key on gas


New member
where is your pulse line located for fuel pump and how far away is it from carb....and what cam do you have in motor
Will this engine run with any other carburetor? Has this carb ever ran for you before? Do you know if its jetted close to being correct for a 390? That is a big carb for a 390 so it will need a lot of rpm to work properly. Im just not sure that its getting enough fuel signal to work prperly for a 390 at low rpm.


New member
Pulse has been taken from everywhere possible

Cam is a .360 lift with 1.3 rockers, so almost .500 lift

Talked to a guy who recommended a higher LPH fuel pump

Going to get that installed and give it a go, it's a 35lph

I believe the culprit to be a weak pulse + low fuel delivery

Pulse line is around 6 inches long

Carb is brand new and just got it back from EC, and they said it checked out. I haven't got to mess with the jets. I need the thing to pump gas first.

Haven't tried any other carb yet