All,

I did a search for these conditions in the engine set up tips but could not seem to find any clear answers.

I have a fox 35 that struggles to run correctly. It appears to burn off its prime and then shut down. It also a day ago or so ran for more than the prime but did  so raggedly - sometimes appearing to struggle to stay alight and at other times running more decently. Decently as in rich but steady.
I have replaced the needle valve with an ST needle valve - re-did all the surgical tubing and  tightened the mounting bolts to get rid of the possibility of a loose mount. I checked the needle valve for the so the fuel hole is pointed in the right direction - it's about in a 4:00 position on a clock face.

I am thinking of swapping out the Tank for a new one and then cleaning the old one.

Is there a Gasket somewhere that is broken possibly - like the one on the Backplate? It seems to draw fuel from the prime enough to get to the combustion chamber but it doesn't continue to draw fuel after it burns off the prime

I'm still fiddling with it - but I am at a loss to figure out what is going on

Any suggestions would be helpful

 

When I use a single hole spray bar I always set the hole at 5 P M  or 7 P M depending witch aide the needle is on, looking at the engine from the prop, and it has always worked for me, hope that this helps..

A rough check of the crankcase seal is to slowly turn the motor over -- as the piston descends, you should hear a "phut" when the transfer ports open.  It's more obvious with the plug out or the head off (you can feel the puff of air on your lips if you hold it close to your face, and you can't confuse it with the compression stroke), but once you know what it is you don't need the plug off.

If it has enough seal to "phut" when you pull the prop through slowly (one revolution every second or two) then I don't think that's your problem.  You could certainly pull it through slower and see (with a perfect seal you could take a year and it'd still "phut") -- but I couldn't tell you how slow is too slow for the test.

   Yes, the short plug could be all of the problem. For the engine to run properly the element needs to 'see" a proper amount of fuel for the combustion cycle to happen naturally. if it doesn't, it will misfire and seem to run rich because it isn't burning the whole fuel/air charge.  I know the Fireball plugs are priced pretty cheap, but if you have to use three to get one good one, what are you saving?  Especially for sport flying, and good quality glow plug should last a long, long time, like a flying season or two.
  Type at you later,
  Dan McEntee

Worthless "me too" post - I agree with everyone else, Fireballs are nearly worthless, due to extremely low yield. When I was running a Fox, many years ago, I used a Fox Standard Long plug with no problems. About 10% or so are bad, but you can weed those out by looking at the element. I was not nearly as picky about it as I would be now, but I ran whatever plugs I could find, and it wasn't at all fussy about plugs.

   The only other plugs I categorically will not use are Rossi plugs. They never had a problem leaking or coming apart, but they seem to cause the "quit like you flipped a switch" problem repeatedly. And it didn't seem to matter which style or type of Rossi plug, they more-or-less all the ones I tried did that, and on various engines, maybe it's something about the alloy of metal in the element, all I know it they are poison.

    Brett