Engine won't start!! :(

[scas75]

ok, so I picked up a trainer yesterday used, said it had been sitting for 2 years., so sure enough it needed some work done to it.,, first off the carb was stuck closed, I took it off cleaned and managed to free it up, now it operates nice and smoothly! put it back on ., checked the fuel lines looked good, put a new fuel tank I had and filled it up., fuel flows properly through the lines... also I removed the glow plug and squirted a touch of lubricant and turned the prop back and forth till it was moving freely and replaced with a new glow plug...
tried to start it and it sputtered a few times but then I noticed the freekin prop was getting loose, wow that could have been ugly, I removed the prop and re seated everuything in order and tightened it back up really good! ok problems solved up to this point.

NOW, the engine at times wants to start but never fully gets going., I have the idle mixture screw set to 2 full turns out ...I am noticing the carb is shooting out fuel as I turned the prop, nothing major but I can see some liquids coming out...
the engine is .40 series o.s. I believe its a os maxx 45? or 46 let mk now if anyone had this experience and how they resolved it? please and thank you

 

[tntpoof]

did you check glow plug to make sure it was working?

 

[scas75]

yes glow plug is working good, I put a brand new one in, plus I tested my glow starter on another pug and it works good

I've been using a stick to turn the prop to start it, but only fires up for a second. I'm waiting for my field kit battery to finish charging then I will try it with the electric starter

I wonder if there is a fast idle screw I need to adjust there is a screw inside the throttle cable connection and another screw on the outside portion of the carb facing the body of the engine,...

 

[tntpoof]

no confirmation glow plug is working .works on others.

 

[scas75]

the glow plug is ruled out as not the problem at this time... but i see what you're say., although I'm wondering if it has anything to do with it not getting enough air mixture??

 

[tudordewolf]

yes glow plug is working good, I put a brand new one in, plus I tested my glow starter on another pug and it works good

I've been using a stick to turn the prop to start it, but only fires up for a second. I'm waiting for my field kit battery to finish charging then I will try it with the electric starter

I wonder if there is a fast idle screw I need to adjust there is a screw inside the throttle cable connection and another screw on the outside portion of the carb facing the body of the engine,...

Posting a pic of the carb might help. Does it look like this?

If it does, tuning is slightly different than for a car/truck carb. A "surface" carb has a High-speed needle, a low speed-needle, and an idle-gap adjustment screw, which determines the minimum opening of the throttle and thus idle. The reason for 2 mixture needles is that you can achieve a lower idle with a leaner tune than would be suitable for full throttle, (the fuel-air mixture appropriate for full throttle would bog down in the lower RPM ranges), so you want to option to separately adjust the fuel-air mixture at high and low throttle settings.

This is important in a car that spends most of its time accelerating or decelerating with rapid changes to throttle input.

This is less important for an aircraft engine which will spend the vast majority of its time producing steady power high in its output range.

An aircraft carb will often only have 1 needle valve to adjust fuel-air mixture and and air-bleed screw which you use to adjust idle, though in a slightly different manner than one does for the surface vehicle. The carb pictured above is one of these - you see the screw that goes in "sideways", parallel to the throttle arm's axis of rotation, and the hole in the front of the carb? That's the air bleed.


It produces the same fuel-air mixture throughout it's entire throttle range, and lets in air through a secondary passage adjusted by the air-bleed screw to achieve a lower / leaner idle, effectively leaning out the fuel air mixture only at minimum throttle settings when the air bleed becomes a significant portion of the air being let in.

There's a thread discussing tuning them here.