poolman

os fx .46 1 month old, ran 1 gal thru it ran fine. now runs ok for awhile then dies, dosnt matter if full throttle or half. played with it and seen air in short fuel line between neddle valve and carb. checked tank and lines "all good" . could my needle valve be leaking air? or mabe not enough exhaust pressure with my os muffler?

big max 1935

My Feedback: (9)

The fuel line between the needle valve will never be full of fuel ,all thats in there is just what the needle valve lets in. Some times they look like they have air in them. As long as your needle valve "O" ring is not damaged it should not leak air. Maybe your second gallon of fuel is not up to par. Doubt if OS would put out a muffler that didn't have enough pressure . Try a new plug. MAX H.

Spicoli

My call would be your needle valve is leaking air.you shouldn't be seeing bubbles going into the carb.I made an extra o ring out of fuel tubing and it fixed my problem with more than one 46 fx

Spaceclam

you should never see fuel in the line at all. it will always be full, but because of the restriction of the needle valve, it will only move as fast as it allows. big max, if you are seeing fuel in your lines i would fix it right there. that is possibly damaging, and makes it much harder to tune, plus performance will be at a record low. personally i have never had a problem with a .46 fx, the only ones i have seen are perfect examples of top line engineering. just try the fuel tubing idea as os charges a lot for everything. a right angle bend on their four stroke's exhaust manifold is $30!. i will bet o-rings are at least $5.

big max 1935

My Feedback: (9)

You should see a line full of fuel to the needle valve ,you won't see it in the line from the needle valve to the carb. Just what the needle allows in it. MAX H.

Spaceclam

if it is an air bleed needle valve, than yes, youa re right. but the fx series do not have air bleed.it is simply like a valve. for instance, when you close a valve to a pipe, you shold not see any air, it just let's it in slower. being it is not an air bleed needle valve, the only way for air to get in is to leak in, because the needle valve should not be pulling air

ShempHoward

My Feedback: (3)

Vibration from a poorly padded tank and/or prooly balanced prop will produce the same symptoms and cause bubbles to appear in that short piece of fuel tubing there by resulting in erratic engine performance.

Spaceclam

whether you choose to believe it or not, my .46 la vibrated so badly all of it's life that it caused the fuel in an overpadded tank to foam. i know we did not do anything wrong because i had the seasoned pilots who have had nothing but os engines all their life break it in for me

poolman

thanks for reply;;
I have tryed everything but i think leaking o ring sounds right to me . is there a grease i could use to seal it
or can i get a thicker o ring if the cut peice of tube does not fit or seal?

Spaceclam

maybe form-a-gasket, but i am not sure if that will contaminate the fuel or not. just try the piece of rubber.

Matt Kirsch

My Feedback: (21)

Putting plain old Vaseline on the existing O-ring will tell you if that is where the problem is. If that cures the problem, simply get a new O-ring, the right O-ring, the one OS supplies with their engines.

Check for loose fuel nipples too.