Ryobi PLT 3043A whipper-snipper leaking oil and not starting?

I need some help with my Ryobi PTL 3043A line trimmer.

It was leaking oil badly then one day it conked out mid-use. I also noticed alot of fuel had disappeared from my tank - very unusual.

I took it apart and found the oil was leaking mainly from the muffler. I've put a fresh mix of fuel in (however the suction nozzle in the tank looks a bit brown - possibly clogged up?).

The throttle, primer bulb and choke are all operating perfectly. It is getting spark and perfect compression. I've cleaned and tested the spark plug and it sparks nicely. A check inside the piston chamber showed alot of black residue on the top of the piston but the sides are clean and well lubricated.

It is hard to tell if the carbie is getting fuel properly but pressing the primer bulb seems to move alot of fuel through it with no hassles.

I've left the muffler off and tried starting the trimmer and when I pull the starter cord, I can see small puffs of bluish smoke leaving the exhaust hole. I guess this is just some old oil that the spark plug is burning?

Perhaps the fuel nozzle in the tank is my problem? Not being able to suck enough fuel?

Perhaps its a buildup of gunk on the piston?

I did get the trimmer to start once after cleaning the spark plug - it operated ok for about 15 seconds on half throttle but then when I opened the throttle up a bit more, it conked out again and hasn't started since.

Does this sound like something obvious to anyone? Is there a spray or fuel additive or something I can use to clean the fuel lines through the engine?

I'm off to the hardware store now to see what is around. Any help would be great.

Cheers,

Quinny,
Australia.