OS .46 LA Surging Problems
 

I have an OS .46 LA and I've flown it for a few years and lately I have had problems with it surging while in the air and dying after it surges. When it does this, it is almost always when I am flying into a stronger wind and sometimes when I'm in a steep climb. I adjusted the high speed needle but that seemed to make it worse so I put it back to where it was. Also, it seems like there is a lot of engine vibration when under idle up to about half throttle and then at higher throttle it's not as bad. Anyone have an idea of what is going on? Thanks.

RE: OS .46 LA Surging Problems
 

On the ground, adjust the high speed needle for maximum RPM then back it off a few clicks (richen it) until it drops 200-500 RPM.

The adjust the low end until you get a smooth, prolonged idle, good transition and smooth running at part throttle. Remeber that the LA's carb has an air bleed low speed mixture screw. This means it is opposite of most other carbs. In other words in is rich and out is lean.

If that still doesn't do it, look at things like fuel lines (including inside the tank), glow plug, trash in the carb, etc.

RE: OS .46 LA Surging Problems
 

sounds like either foaming in the fuel from vibration, or a air leak into your fuel lines somewhere

RE: OS .46 LA Surging Problems
 

Everything chuck mentioned plus check the prop for balance. This engine isn't a real vibrator unless something is loose or out of balance. check the motor mount screws too, all 8 of them.

RE: OS .46 LA Surging Problems
 

I flew the engine the other day and I had been flying for a few minutes when the engine died out of nowhere and I had to deadstick my plane ending up doing a cartwheel on the ground. I checked all of the fuel lines and there wasn't much vibration.

RE: OS .46 LA Surging Problems
 

Hi!
Are you sure you have a tank that is working properly (240cc) and that you use a 11x6 APC prop...and OS 8 or Enya 3 glowplug???
Fuel: 5-15%nitro.

RE: OS .46 LA Surging Problems
 

For this last flight, the tank was brand new because I put the engine onto a brand new plane. I put on a new 11x6 prop in case of vibration problems and I do have an OS #8 glowplug in it. I'm thinking about trying a new glowplug.

RE: OS .46 LA Surging Problems
 

i had a similar problem with a os .40 fp (similar to the LA series, has an airbleed carb) it would die on me at about 1/3 throttle and would vibrate badly at idle.
the problems was simply carb adjustments, you have to learn how to tune these airbleed carbs. (my highend was a little to rich and my low end was a tad to lean)
the main needle valve controls all fuel adjustments, this works fine at full throttle but the problem is it floods the carb at a lower throttle setting. thats what the airbleed screw is for, to lean out the mixture.
basic tuneing is as follows, set the airbleed screw halfway into the little hole (you can use a pin or just look at it), then go to WOT and set the high speed needle.
go back to idle and let it sit for 30 seconds, then "floor it" to WOT again. if the engine pauses then revs the mixture is to lean CLOSE (tighten) the airbleed screw some more (in 1/8 increments), let it idle for another 30 seconds then floor it again. if it starts to stumble (sounds like its missing/loaded/or just this gargleing sound) then loosen aka lean the airbleed screw. try this again and again until you floor it and it instantly gains rpm's (a little gargle is acceptable)
now what i have noticed, is i tend to set the highend a little to rich this really messes up the midrange, so i slowly advance the throttle one click at a time (1-2 second pause inbetween), listen to the engine and see if it starts to gargle, if it does lean the high end just a few clicks and see if it goes away. (it should)
since i figured that out i havnt had a deadstick, im useing a pos gms glowplug and either a 12.25x3.75 or 12x4 apc prop

RE: OS .46 LA Surging Problems
 

Thanks JimmyJames. I checked my glowplug and I was wondering how you can tell if it's in good condition or not. Does the coil have to light up all the way to the end if it's good?

RE: OS .46 LA Surging Problems
 

I flew it again before getting a chance to buy a new glowplug. I tuned the engine and it seemed fine and I had one flight that went fine except about 7 or 8 minutes in I did a loop and the rpms went way down and then it came back up. In the next flight, I was about 7 or 8 minutes in again and the engine died. It seems that it has the problems when it is later in the flight like this. I would normally think it was a problem with the weight in the fuel tank but it has happened on two different tanks like I said earlier.

RE: OS .46 LA Surging Problems
 

Hi!
Have you mounted the tank according to the "tank rule"?
A 240cc (8oz) is the size you should use.

RE: OS .46 LA Surging Problems
 

Does the "tank rule" involve the size of the tank? I think the tank is a 10 or 12 oz. tank.

RE: OS .46 LA Surging Problems
 

Make sure all your engine bolts are tight. I remember one with loosed head bolts once that would do weird things.