Go Back  RCU Forums > RC Airplanes > Beginners
Reload this Page >

Problems starting my OS 46 LA

Beginners Beginners in RC start here for help.

Problems starting my OS 46 LA

Old 09-08-2009, 04:49 PM
Junior Member
Thread Starter
Join Date: May 2009
Location: Pearland, TX
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
Default Problems starting my OS 46 LA

I have experience with electrics but this is my first nitro. I am having trouble getting my OS 46 LA started and keeping it running. I have to prime the heck out of it just to get it to turn over. If it stays running, I can get the needle valve set to a rich "run-in" setting but it will die on me after about a minute. I have heard about a "tank rule", any word on this? It seems that the needle valve isn't behaving like the manual says. I have the carb set at 1/3 open while turning the prop over. I this right?

I haven't even run a full tank through it yet and I already need another chicken stick. Any advice is greatly appreciated.
Old 09-08-2009, 05:31 PM
MetallicaJunkie's Avatar
Join Date: Sep 2006
Location: Donna, TX
Posts: 5,461
Received 1 Like on 1 Post
Default RE: Problems starting my OS 46 LA

sounds like you have it too rich, being that it quits on you at a higher throttle setting. Try to set the tank so that the fuel lines coming out of the tank are the same height as the carb
Old 09-08-2009, 05:38 PM
Norm Nestie
Join Date: Apr 2002
Location: Gabriola Island, BC, CANADA
Posts: 414
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Problems starting my OS 46 LA

Ok, first make sure all looks ok inside the tank ( pick up line connected, etc.) no splits in fuel line. Make sure center line of tank is pretty close to the height of the spray bar. Don't want your tank too high or low relative to the carburetor. Fuel is OK? Alright, gently turn high sped needle in (clockwise) til it seats. Now turn it out about 3 turns. That should be a good place to start (rtich). Glow plug OK too? Fire it up a let it run about 1/2 throttle foe a few minutes and slowly throttle up to full speed and hold there for 15 seconds or so then slowly throttle back to half throttle and then up again 3 or 4 times. Now throttle up and with it running max turn high speed needle in 1/4 to 1/2 turn to start to lean it out a bit Watch your fingers!!See how it runs at that point and you can evventually lean it out some more to get it running where you want it . If you have a manual consult it as well and as much as possible follow its' instructions. If all else is ok this should be a pretty easy motor to get running well. You may need to tweak the low end too, maybe not . Do you go to a flying field? the best advise is probably there, talk to one of the experienced fliers. Good luck.
Old 09-08-2009, 06:02 PM
Senior Member
My Feedback: (1)
Allfat's Avatar
Join Date: Apr 2008
Location: St Paul, OR
Posts: 400
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Problems starting my OS 46 LA

Edit: Posted in wrong thread, moved to that thread.
Old 09-08-2009, 06:13 PM
Senior Member
ChuckW's Avatar
Join Date: Jun 2006
Location: Clovis, CA
Posts: 5,165
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Problems starting my OS 46 LA

Where is the high speed needle? Is it at the factory setting? Are you sure the fuel plumbing is correct and leak free? (not just fuel leaks but air leaks too). What position is the engine mounted in?

If everything looks OK, I'd say it is rich based on your description although it is difficult to say exactly without being there. Get it started and slowly advance the throttle to full. It will likely be spitting and blubbering. Turn the needle valve in a couple of clicks at a time and give it a second to take affect. Hopefully the RPM will increase a little and the engine will smooth out slightly each time. Do this until you get a good, smooth sound from the engine then, since this is a new engine, turn it back the other way a few clicks to richen it a little.

You may also want to get an electric starter. Flip starting is great on an engine that is broken in and well tuned but it can be frustrating on an engine that is new with an unknown mixture setting. Not saying it can't be done but the electric starter makes life much easier.

Unless your tank position is way out of whack in relation to the engine I wouldn't worry too much about it. I may catch a little flak for this but I think the whole tank positioning thing is a little over-rated these days. There are plenty of ARF's out there with tanks in supposedly less than ideal positions with engines that run excellent. In fact the tank change position in relation to the carb frequently in flight based on the airplanes attitude. If the engine is well tuned, you almost never notice it.

I have had idle mixture problems on engines with air bleed card such as the .46-LA when they are mounted inverted however.

The other thing I'd recommend is going out to your club field and see what one of the more experienced people think about your problem. Look for the guy who's engines just start and he flys with no hassle. Avoid the guy who's engines don't want to start or he just sits adjusting and tinkering with them half the day.
Old 09-08-2009, 06:33 PM
Senior Member
sportrider_fz6's Avatar
Join Date: Jan 2008
Location: Pueblo West, CO
Posts: 646
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Problems starting my OS 46 LA

on my OS engines (2 .46 LA, .40 LA, .25 FP, .46 AX) I've ran them all in the same way, following the instructions. I'll start at 2 1/2 turns from closed, open the throttle 1/2 way,(if your using a chicken stick, plug the exhaust port and with the igniter disconnected flip the prop until you can see fuel reach the carb. if your using an electric starter there is no need to prime the engine) attach the igniter to the glow plug (make sure any loose clothing is tucked in and clear of the prop!!!) flip the propeller until the engine starts. once the engine is running, advance the throttle (slowly) to the highest setting. keeping your fingers clear of the prop arc, slowly turn in the high speed needle until you hear the highest rpm the motor will turn, if you go too lean the engines rpm will drop. run the engine at the highest rpm for 5 seconds, then turn the high speed needle out until you hear the engine "4 stroking" (it will blubber, and be smoking noticeably) run the engine at this rich setting for 5 seconds. then lean the engine out. you will do this for the first full tank. once the tank is empty, let the engine cool completely down with the throttle fully opened and the piston at bottom dead center. after the engine is cool refuel the tank and restart the engine. bring it to full throttle lean the engine out until peak rpm is heard then richen the engine until you hear a slight drop in the rpms. this is where the engine should be tuned. an LA engine doesn't have a low speed needle, it uses an air bleed screw. to adjust this, bring the engine to the lowest stable idle you can. let the engine idle for 10 seconds then bring it to full throttle if it loads up and sputters shut the engine off and open the air bleed screw 1/8 turn restart the engine open the throttle to full then bring it to idle and for 10 seconds again. continue this until the engine transitions smoothly from idle to full throttle. if the engine dies after idling for 10 seconds when the throttle is opened the air bleed screw will need to be turned in.

hope this helps you out. I strongly recommend getting an electric starter. I find the break in process a lot easier as well as fly days, with the starter. I started my planes for the first year with a chicken stick, after I bought a starter I'd say it was one of the best purchases I've made in this hobby so far.
Old 09-09-2009, 06:12 AM
mclina's Avatar
Join Date: Dec 2006
Location: Westford, MA
Posts: 1,809
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Problems starting my OS 46 LA

I also have several LA's and one thing I found is that they run REALLY rough for the first couple of tanks. I couldn't get anything close to an idle out of them until about the third tank, and when they are new, they shake like crazy. After a few tanks, they settle down, and they are great running engines that require almost no adjustment.

I also found that they are typically rich at the recommended setting of 2 1/2 turns out. Some of mine run at 2 turns or less, but be very careful about leaning it out too much. They are pretty forgiving, and will tolerate a rich setting for initial break in. Just run it wide open for a couple of tanks before you try to get it to idle.

Good luck
Old 09-09-2009, 11:39 AM
Senior Member
My Feedback: (3)
billd76's Avatar
Join Date: Jan 2009
Location: Nottingham, PA
Posts: 1,183
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Problems starting my OS 46 LA

I just got a 46LA and here's is a direct copy from the manual on initial needle setting "Open the needle-valve 1 1/2 turns (for 40,46LA) and 2 1/2 turns
(for 65LA) in the direction of arrow from the closed position". And this is for intitial break in

All internal-combustion engines benefit, to some
degree, from extra care when they are run for the first
few times - known as running-in or breaking-in. This is
because the working parts of a new engine take a little
time to settle down after being subjected to high
temperatures and stresses. However, because O.S.
engines are made with the aid of the finest modern
precision machinery and from the best and most suitable
materials, only a very short and simple running-in
procedure is required and can be carried out with the
engine installed in the model.The process is as follows:
1) Start the engine and, with the throttle fully open,
open the needle-valve an extra half turn (180°)
from the optimum setting. This will produce a rich
mixture that will result in cooler running. Allow the
engine to run out a full tank on the ground. (Avoid
dusty surroundings.)
2) Now fly the model with the needle-valve re-set 20-
30 degrees open from the optimum setting ( i.e.
40-60° from the highest rpm setting ).
3) Close the needle-valve very slightly on successive
flights so that the engine is running on its optimum
needle setting at the fifth or sixth flight.

I followed the inital 1 1/2 turns, primed maybe two blips and it fired right up ( I use a starter).
I have ran three tanks of fuel through the engine thus far, for the first two tanks (with needle backed out 180 from 1 1/2) , it would not idle. 3rd tank it did much better. idles well. hope to maiden it this weekend. What size prop are you using?
Old 09-09-2009, 04:36 PM
Junior Member
Thread Starter
Join Date: May 2009
Location: Pearland, TX
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Problems starting my OS 46 LA

Thanks for the advice. Got out this a.m. and tried a few of the bits of advice. Got it running and ran 2 tanks through it. I ran one tank through it with WOT and the needle valve set at about 2-1/2 turns open. It ran just fine. The next tank I adjusted down to about 1-3/4 open. It did well also. WOT my tach is reading about 11,500 rpm and the lowest idle that I can get is about 4,500 rpm. I am running 10% fuel with the recommended 11x6 break-in prop. Do these numbers look alright to you guys?
Old 09-09-2009, 04:54 PM
Senior Member
My Feedback: (1)
bkdavy's Avatar
Join Date: Sep 2004
Location: FrederickMD
Posts: 2,114
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Problems starting my OS 46 LA

That engine should easily idle between 2500 and 3000 rpm. With the engine running at wide open throttle, lean it out to the peak and then richen it up 300-500 rpm. Now bring down the idle and adjust your throttle trim to bring it as low as you can. The low end is set a little rich from the factory, so you might want to make a small adjustment to the airbleed screw, but not before you've checked your throttle transition. The manual for the LA explains exactly how to check it. Once you have the high speed and low speed set, these engines are nearly bulletproof, and are easily started. As you've already discovered, they tend to like to be a little "wet" to start.
Old 09-09-2009, 08:56 PM
Senior Member
Alex7403's Avatar
Join Date: Jun 2004
Location: New york, NY
Posts: 1,594
Likes: 0
Received 0 Likes on 0 Posts
Default RE: Problems starting my OS 46 LA

I had something like this issue with 46 LA.
One thing to check with the 46 LA is the back plate if its secured, sometimes its getting loose just a bit and sipping air.
make sure the screws are tight with blue thread lock, but not too tight.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.