Need some help please. I am having engine issues with both trainers that I have.

First I have my Alpha 40 with the Evolution .46 NT engine that is supposed to be a great engine for a beginner. We (myself and my various trainers) cannot get the engine to run consistently. Initially we though it was a fuel line/air leak issue. I have replaced the tank and all the lines. Engine gaskets as well. I used dubro fuel line clamps to ensure that there were no leaks. The initial issue was that when I advanced to full throttle the engine would die as if it was not getting any fuel. We adjusted the needle valve so the mix was rich, and you can hear the engine slowing reving up as the mix was too rich, but when it got to full RPMs it died. Now we have adjusted the needle valve enough to run a full throttle, but when you go from full throttle to mid throttle, sometimes it dies as well. We have also adjusted the low speed idle on the carb as much as possible, the engine is not running consistently at all. Put in two new OS A3 glow plugs for good measure - it just won't run well. Any Ideas?

Second is an OS 40 LA that just will not run, it will start and run rough for 10-15 seconds, but once you remove the glow starter and get it to about mid-throttle it dies within a few seconds. I added a new neddle valve and lines are new, as this plane has never been flown. It is a brand new tank. As a matter of fact, I pressure checked both tanks for leaks - no issues. Replaced the gaskets. It will never get to full RPMs, it seems that it is not getting enough fuel to go past mid throttle no matter how rich we make it or adjust the low speed screw.

Any ideas? I have not flown since about October, and I am ready to just throw in the towel.

Hmmm.

Same problem two different engines!

Sounds like you've got some bad fuel.

If you've left the bottlle unsealed, it will absorb moisture, and be virtually worthless.

I would either borrow a tank full from a friend or buy a new jug

Well, the jug was sealed but older. Used a new jug of S&W at the field towards the end of troubleshooting, and it seemed to improve somewhat, but still the same issues.

How do you have the needle valve set at on the .40 LA. ? 2 1/2 turns using 15% fuel is flawless. I just discovered my crank case is cracked and every thing you are describing is happening with my egine now.

Since this is a second hand engine, I am starting to think the OS might be a lemon - and that is why it was sold. How did you determine where the crack was?

We started at 2.5 turns for the OS LA 40, and worked from there. From other posts, I think the culprit on both is the low speed needle valve. Do you know the setting for the OS 40 LA for this?

Sounds like you have the wrong needle valve , My OS .40 LA doesn't have a low speed needle valve. But it does have a carb bleed screw. This srcew is located on the carbs body . When I get my camera going again I will post pics. As far as it being a lemon I doubt it but one nver knows.

I found the crack to when I took the back plate off . I had this plate off 2 times prior to today and never noticed it . It is a hair line crack right underneath the flanges for mounting. The one reason I new I was losing compression was because when I first bought this engine used , I was able to crank the shaft with my hand over the muffler's exhaust pipe and fuel would flow into the carb.

How much did you pay for the engine ? might by it from just to use the parts

as far as the evo46 had the same prob and solved it by drilling the holes in the baffle to twice the size and now runs a lot better but i still think its a seconde rate engine.

Thanks all. Yes I mean the air bleed screw vs. low speed needle valve - still a newbie. Found a website that sells the OS 40LA that said that the "factory setting" for the OS 40 LA air bleed screw is two full revolutions and the high speed needle valve is also 2 revolutions. I will try this, start it up and see if that does the trick. There was a lot in the forums on air bleed adjustments that I will try.

As for the eov .46, apparently there were some problems with the setting of the low speed needle from the factory. I will try these settings (1 1/5 out) on the low speed and see if that works as well. The evo has that retaining set screw the needed to be removed before I could adjust the low speed needle, but RC universe forums helped with that instruction as well.

I'm not sure about 2 full revolutions I had mine set to 1/4- 1/2 turn from closed and it was fine. Becareful with changing the setting on this screw , the turns on it should be down at 1/8 turns.

good luck I hope it works.

Thanks for the tip. We will try the two revolutions. If there is no luck, then I will close it down and try 1/4, and go about 1/8 until I get to 1/2 and see how that works

Remove the baffle on the EVO and try it that way, I bet it will run just fine..

Mike

I have read that too in some of the posts. Nut sure I would recognize it if I stumbled on it. Do you have a pic you can send me? Mike

It's inside the muffler. Take the muffler apart and it's the round disk inside the muffler. Take it out and I bet it will run just fine. You may need to reset your needle settings if you have messed with them too.

Mike

Hi!
The idle adjustment screw on the OS LA engine is not at all critical.
In could not be your problem!
All (OS) engines just run fine if you provide the right things: Fresh air, Fresh fuel and fire.
It's that simple!
I hope you tightened all screws on the engine and checked fuel so that it fresh. I have 10 year old glow fuel that works just great so I don't mean "New" in that sense... I mean it hasn't been contaminated by drawing moisture from the air, having the fuel cap open long periods is not good, especially in a damp and hot climate.
Glowplug: a Enya 3 or OS 8 glowplug.
Fuel: 5-15% nitro
Propeller: 11x5 or 11x6 APC if used in a high winged trainer...not a 10x6 please!
Tank: 240cc (8oz). Do not use a bigger tank than 300cc (10oz).
High speed needle open 2 turns. This is a standard setting on most engines...adjust it from here.
Al OS LA engines are super reliable and will give instant throttle response direct from the start. Very little running-in is necessary.

Idle needle on this engine is an air-bleed needle, it governs the amount of air coming into the carb at low speed. You can see the hole up front on the carb where the air comes in. factory setting on every OS with air-bleed screw is: hole half closed by screw, adjust it from there, mostly you have to open it some.

Regards!
Jan K
Sweden

Jaka, Hi - I did have a 10X6 - will try and 11X5 or 11X6. Switching to wood anyway, since it is safer than the plastic. I also have an OS A3 glowplug. I will try and OS8. Will take a look at this "hole". I did read that 2 turns on the airbleed is standard as well, but will try both. I believe the tank is 240 CC - and it is a high wing trainer. Thanks all for the tips. Mike