Engne Tuning help needed - RCCanada - Canada Radio Controlled Hobby Forum
RCCanada - Canada's Radio Control Hobby Forum
Engines Discuss engines

Closed Thread
Thread Tools Display Modes
Old 07-03-2006, 12:24 AM   #1
RCC Apprentice
Join Date: Apr 2006
Location: Guelph, Ontario

Feedback: 0 / 0%
Posts: 63
Total Props: 0
Engne Tuning help needed

       Remove this ad - become a site supporter!
I have an OS 46 LA (the blue one) on my trainer, and I have been told how to tune it but I keep forgetting. I have an Idle adjustment, and a mixture adjustment. I need to know what to listen for at full throttle when I raise the model up, and then which way to turn the screw to fix it. Any help is appreciated.

tvguy is offline   Quick reply to this message.

Sponsored Links - Subscribe to remove this ad.
Old 07-03-2006, 12:31 AM   #2
RCC Supreme Contributor
I am: Dave
Join Date: Jul 2004
Location: P.River,Alberta
Radio of choice:
Airtronics SD-6G
# of RCs: 3

Feedback: 116 / 97%
Posts: 6,081
Total Props: 6
The Nose


When you hold your nose up, if the engine wants to die, then you are too lean and you must open the high speed needle more going more counterclockwise.

When you tip the nose down, if the engine blubbers, then you are too rich so turn the needle opposite.

From idling, if you punch the throttle open and it stops, you are too lean and must open the low needle more counterclockwise. If it stutters and then dies, it is rich.

Cassat Run 10 X 6 APC
cassat is offline   Quick reply to this message.
Old 07-03-2006, 08:09 AM   #3
RCC Apprentice
Join Date: Apr 2006
Location: Guelph, Ontario

Feedback: 0 / 0%
Posts: 63
Total Props: 0
engine help

Thanks, I'll have to either print that out or write it down so I don't forget. I have been told that a couple of times, but still seem to forget.
tvguy is offline   Quick reply to this message.
Old 07-03-2006, 08:55 AM   #4
Wayne MIller
RCC Supreme Contributor
I am: Wayne MIller
Join Date: Aug 2004
Location: Kitchener/Drumbo, On
Radio of choice:
Hitec A9 JR 9303
# of RCs: 19

Feedback: 11 / 100%
Posts: 2,168
Total Props: 8
Engine Tuning


I've published this here before, but can't find it. It is meant to help someone to tune an engine from scratch. It may be helpful in the future. I hope you find it helpful.


Wayne Miller


If your glow plug is OK, you don't have old fuel, your fuel delivery system is OK, no engine air leaks and the spray bar is positioned correctly, if needed (as per manual) then you may want to try the following initial set up.

First, try resetting your needle valves to an initial start position. To do this, open carb to about 1/4 throttle setting. Turn high end needle about 5 turns from closed. Open carb to full throttle and use a clean piece of fuel tubing attached to the carb intake nipple and blow gently into it with your mouth - listen for air going into the carb (a hiss) - if you don't hear air, back out the high speed needle valve a little and try again - keep doing this until you hear air. This ensures your high end needle will allow fuel (in this case air) to flow into the carb. If it doesn't, than try another turn out or find out what is the obstruction.

Once you've verified the high end needle valve is working properly and allows air to be blown into the carb at full throttle, you need to set the low speed valve. To start, keep the same high end needle setting at 5-6 turns out and close throttle to about 1/4 throttle setting. Turn low end needle valve so it is completely seated (meaning closed by turning it clockwise, do this gently and don't force anything). Now with the carb opened at 1/4 throttle setting, blow air into the fuel tubing and SLOWLY rotate the low end needle valve counterclockwise (to richen the low end mixture). Stop richening the low end needle valve when you first "feel", or more accurately, hear (a hiss) air leaking into the carb.

Now, return to high end needle valve and close it completely and open it about 2 1/2 turns from closed. Recheck to make sure this 2 1/2 turn setting allows air to flow into carb when you blow air into the fuel intake nipple. Then double check the low end needle setting to see if you can blow air into it with carb at 1/4 throttle setting.

If all checks out, then attached fuel tank line to engine, prime engine manually (a few drops of fuel in the carb opening), return to slightly less than 1/4 throttle, attached glow driver and flip the prop, or start with starter. Most engines start better at 1/4 throttle than full throttle.

For the next step, remember turning the needle valve counter clockwise (out) makes the setting richer, turning the needle valve clock wise (in) makes the setting leaner.

As soon as the engine fires up, don't touch anything and let it run. Leave glow driver on and let engine warm up for about 30 seconds. Now with glow driver still on, slowly advance throttle setting. You should be able to get it to full throttle. If it dies from going from 1/4 to 1/2 throttle and above (with glow attached) it probably means you are too lean on the low end needle valve. Just open it (low end needle valve) up a little bit (about an 1/8 of a turn or less). Repeat the process as necessary until engine can advance above 1/2 throttle without dying. Once it can run at 1/2 and above, remove glow driver and go to full throttle. At full throttle, lean out high end needle valve to max lean rpm and then richen the high end needle mixture by 400 rpm (when richening, the RPM will drop slowly) or so when you pinch, and release, the fuel line briefly at full throttle the engine speeds up a little and then returns to its setting. The pinch test verifies if you are too rich or too lean. If you are too lean, when you pinch and release the fuel tubing the engine will die or not speed up at all. If you pinch and release and engine speeds up a lot, you are too rich, etc..etc.. The right setting is when your engine speeds up a little, about 300-400 rpm (a tach would help with getting your ears tuned in this area)

Have fun and if you use this methodical method to tune your needles, you will get a good "feel" for how to set carbs quickly and easily. Remember, high end needle normally works at 1/2 throttle and above and low end needle affects the idle and transition to full throttle. Also, if you readjust the low end needle valve, you must recheck and readjust high end. The two needles can interact with each other. If you forget which direction to turn the needle, just use a clean piece of fuel tubing attached to the carb and blow into it to determine if your adjustment reduced the flow or increased the flow for whatever needle you were adjusting.

Its really simple once you get the hang of it.
Wayne MIller is offline   Quick reply to this message.
Old 07-03-2006, 08:56 AM   #5
RCC Master Contributor
Ramz's Avatar
I am: Mark Ramsay
Join Date: Jan 2006
Location: Petitcodiac, New Brunswick
Radio of choice:
Anything but Futaba, Hitec and Airtronics

Feedback: 21 / 100%
Posts: 1,429
Total Props: 5

check your engine manual as it should also have instructions on how to tune the motor.
Ramz is offline   Quick reply to this message.
Old 07-03-2006, 09:43 AM   #6
RCC Supreme Contributor
I am: eric q
Join Date: Jun 2005
Location: Crawford Lake, Ontario
Radio of choice:
# of RCs: too

Feedback: 9 / 100%
Posts: 7,159
Total Props: 26
Re: ...

Originally Posted by Ramz
check your engine manual as it should also have instructions on how to tune the motor.
Right! exactly so since the the 46la has and air bleed screw, not two needles. Air bleed for idle settings (open for lean) and needle valve for high speen settings (close for lean).

Borrow a tach. Start at 2.5 to 3 turns, then set the needle for highest RPM with engine running full speed, then open (richen) needle to reduce by approx. 300 RPM. Small adjustments, wait, measure, small adjustment...

Benchmark: I get 10500 RPM with an APC 12.25x3.75 and 5% fuel on my 46la.

Set the air bleed screw for reliable throttle transition, the methods suggested above work well.
desiderantes meliorem patriam
To err is human, to moo is bovine
moo is offline   Quick reply to this message.
Closed Thread

Quick Reply

Register Now

In order to be able to post messages on the RCCanada - Canada Radio Controlled Hobby Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

Member names may only be composed of alpha-numeric characters. (A-Z and 0-9)

!!ATTENTION ADVERTISERS!! If you intend on advertising anything on this forum, whatsoever, you are required to first contact us here . Additionally, we do NOT allow BUSINESS NAMES unless you are an Authorized Vendor. If you own a business, and want to do sales on this site via posting or private message, you will need to follow the rules. Shops, Stores, Distributors, Group Buys without being authorized will see your account terminated.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Your Name
Your first name and last initial is required if you plan on using the forum.
Which city & province you live in. This is mandatory for classified listings.
Radio of choice?
Which radio is your current favorite to use?
Number of RC Vehicles?
How many boats, cars, planes do you own?


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
vBulletin Message

Thread Tools
Display Modes

Forum Jump

All times are GMT -5. The time now is 08:23 AM.

vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.