Hi Guys
I run an Irvine 46 in my low wing trainer which seems to have gone unreliable.
It's been great, starts easy and no dead sticks, but last Sunday at the field it started to play up.
I always hold the plane vertical to check engine is running right before I take off but this time the engine died after about five seconds, and I noticed a lot of air bubbles in the feed tube that I hadn't seen before?
I am sure that I have the needles set right, so I would appreciate some help.

Thanks
Don

G'day Mate,
When you hold the plane nose up, does it increase revs slightly, If yes, it is rich enough, If not it is too lean.
Also the air bubbles in your fuel line, must be coming from a pin hole or other source inside your tank or fuel line from your tank. check it out, because this will cause it to run lean.

When an engine that was running well begins to act up, replace the glow plug. That is ALWAYS the first thing I check. 99% of the time, that will fix the problems.

If that doesn't fix it, pull the carb off, remove the needle valve and the barrel, and make sure all the small passages are clear. A small particle can be easily trapped in the needle or spray bar assembly. After reassembly, go through the tuning process again.

If that doesn't fix it, check all your fuel lines, including INSIDE the tank for any small holes. Oh what the heck, fuel tubing is cheap, and since you've got it out of the plane anyway, just replace the plumbing.

If that doesn't fix it, try new fuel.

These four steps should fix 99.99% of the problems. If these don't fix it, then you need to start looking for other airleaks that might have developed. Are the head and backplate screws tight? How do the bearings feel? You may need to remove the backplate to visually inspect the rear bearing. Is the piston binding? Is there still good compression? How old is your fuel?

Good Luck
Brad

If you are seeing air bubbles then there is the problem as you should not see any bubble at all, air bubbles will let the engine run inconsistently and go lean then shut off. If the bubbles are in the line coming from the tank I would start off the easy way and replace that line. If they continue then pull the tank out and replace the line in the tank from the stopper to the clunk.

OK I think Iv'e got it sorted.
I pulled the tank out and found that the fuel line inside the tank had stretched and the clunk was resting at the back of the inside of the tank.
This was causing the line to kink and restrict the flow of fuel. I'm not sure about the air bubbles but Iv'e replaced all the fuel lines as a precaution.
This should have cured the problem, but I will have to wait till my next visit to the field.
Thank you for the advice, it is much appreciated.
Don

one are that is often done wrong is the lenth of fuel tibing inside the tank,most are too long.the clunk should be about 3/8 of an inch away from the rear of the tank for best results.you will find that even in this location it will still empty the tank.