46LA problems
 

I have a 46 la that has been sitting in a box for about 3 months after a crash. I had cleaned the engine and put it up. I got it out and put it on a new plane and started the engine to check it. It fired up and ran fine. This was my best running engine, never had any problems. Anyway I took this plane out last night and started it up and off we went. The plane was in the air in no time. While tring to trim the plane, (it kept wanting to climb) the engine wanted to stall. I kept turning the plane back down but it did end up going up stalling on me and dead sticking.:eek: Once I got it back down I tried to restart it. It started but would not idle up to full rpms, I've never had any trouble out of this engine, I tried to adjust the needle but it just would not idle back up to full. Does anyone have any ideas? One more thing, Why would it want to climb like it did? the elevator was level. the plane was a little nose heavy but the book said a little nose heavy is good for a new flier.

RE: 46LA problems
 

Did you try closing the needle all the way, the opening 2.5 turns and adjusting from scratch? Sounds like a tuning issue, or an air leak. I would check or replace all of the fuel lines, then close the needle, open 2.5 to 3 turns, go to WOT and start leaning it out.

Trainers should climb with acceleration, even when they are nose heavy. That is by design.

RE: 46LA problems
 

I did close the needle and then open it 2 1/2 turns and then leaned it from there once it was running. and still could not get it to run. my dad was helping me and said he could feel a mist of fuel hitting his hand off and on on the needle valve side. maybe a leak?

RE: 46LA problems
 

I had a crash and found that the fuel lines were damaged, much easier than I expected. Granted I don't have tons of experience, but what you explained sounds like the engine is running lean (wants to quit when you climb, not getting to full RPM), which could be happening as more air is getting in (or fuel escaping) through a leak somewhere.

My OS has been more forgiving than a fairy godmother. It's ran lean, rich, in different conditions, etc. while I was still learning how to tune. Your's is supposed to be more reliable and forgiving than mine, so I'd start with the fuel lines.

Good luck.

RE: 46LA problems
 

I would think that at WOT the plane would climb. I try to trim mine at half throttle for level flight. Regarding the running issue, you might try and remove the needle valve completely and put fuel pressure on the line going to the carb to back flush it. If it had been setting for some time there might be a speck of dirt, varnish or something that is causing it to not run right. Also what about the LSN have you adjusted that?

RE: 46LA problems
 

yeah, a possiable leak.
I generally use sealent and Blue loctite on the back plate to minnize that.
Maybe try re torqing the head screws.

maybe try reaming the air breed hole with a guitar string to clean it.

Mine is rear needle , so to makesure the orifis is clean or the high side, I had to remove
the barral's arm.

Before you take the carb apart...try checking the fuel tank to see if the clunk didn't get
sholve forward during the dead stick landing.

RE: 46LA problems
 

Look closely at the facts, your engine has been involved in a crash, it is very likely to have something broken or bended even if it is not noticeable at simple sight. I would tear down the engine and inspect every item prior rebuilding. You would like to check also the idle screw. (is not a needle valve)

RE: 46LA problems
 

I did check the idle screw. I had it to where when you pull the glow plug at a idle the engine keeps running with no change in rpms. The fuel lines from tank to engine are new, but the short line on the engines old. I'll change all the lines and see what happens. The head screws are tight, the muffler is tight. I need to check the back plate. If that dont do it I'll tear it apart and see whats going on.

RE: 46LA problems
 

Have you tried the glow plug? If it's not an air leak, then I would check there next.

RE: 46LA problems
 

One thing I just thought of is replacing the gaskets - when you disassembled the engine, did you replace the head gasket, etc? These are really one-time-use devices; they seat in a particular position, and when changed do not seal the way they used to. Could be cause of a leak or compression loss or something.

RE: 46LA problems
 

I changed the plug. I haven't changed the gaskets though.

RE: 46LA problems
 

Don't just change the gaskets hoping it will solve the problem. It likely won't. Test them in place.

Dribble a little fuel on the head to cylinder joint, turn to TDC to put pressure in the cylinder, look for bubbles. No bubbles = no leaks.

The backplate can be tested the same way, but turn past TDC, but not so far that you uncover the ports again. Look for bubbles at the joint. Much less pressure here, so it may be more subtle.

I've never had to replace a head gasket, if I keep grit outta them when I assemble. Ditto backplates. If the backplate did leak some, I'd seal it with RTV sealant, sparingly used. I have had leaking backplates, but only due to loose screws.

To me this smells like a simple tuning issue. Either there's crud in the fuel passages, fuel lines, or the needles are mis-adjusted.

Were it mine, I'd replace all the fuel lines (just to be sure none were pin-holed), including in the tank. Then I'd clean the NVA real good, and remove and clean the carb, ensuring all orfices are clear. Then I'd try runnin' it.

J

RE: 46LA problems
 

take the needle out and put a small peice of fuel tubing on the neadle and put the neadle back in, sometimes air will leak around the neadle threads. the plastic neadle valve body could have a small crack in it also. New fuel line all the way around, even the tank gets new line. I had a 6 oz dubro tank on a plane and the factory tank line that goes inside wasn't limber enough and it wouldnt flex enough to get to the bottom or in inverted flight it would go to the top. also check the seal on the tank. the backplates leack also, clean them up and put some RTV silcone on the backplate and lightly tighten it down

RE: 46LA problems
 

Given the insensitivity of the engine to the needle valve, and the fact that the engine won't rev up to full throttle, there is probably a small chunk of crud caught in the HS needle valve. Take the lines off both sides of the needle valve, hook your fuel pump up to both sides such that you can pump fuel backwards through the needle valve. Back the needle out until it just barely stays in the threaded portion, then pump a few ounces of fuel through the needle valve to back flush it. Filter it if you're sending it back to the fuel jug, then clean out the filter.

Now put the needle valve all the way in, and back it out about 2 turns. This is a good point to restart the engine, retune it, and check it.

A pinhole airleak between the needle valve and the carb can also cause this problem, as it causes the engine to run too lean, so replace the line between the needle and the carb.

The LA series are pretty tough. No need to tear it down until you've made sure the needle valve is clear.

Also make sure your air bleed hole on the front of the carb is not plugged with dirt or debris from the crash.

Brad