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Old Feb 18, 2012, 05:59 AM
Reactor G/P 3D Saito 82a
Joined Jun 2010
81 Posts
Question
Saito .82A dies at mid-range throttle

i have a great planes Reactor 3D .46 with the default tank and setup powered by a saito 82A it was running fine for a year or so...then a crashhhhh a pancake one after taking out every thing and ordering a new Sulivan 10z tank as a replacement for the older one and cleaned the engine ( did not touch the HS or LS Needles ) installed all back together on the plane and instead of the Master Air Scre 14X6 i'm using same brand same size but wooden one, problems started.
first it would fire up for 4 seconds then die ??!! i discovered that my intake o ring came out and was leaking air, took it out and installed it back properly now it fires up and all sounds good, flew it yesterday and was idling fine WOT fine then i started to slow down for a slow fly by and i can hear the engine like it wants to quite, i pushed full throttle and took off to a higher altitude and it feels ok now so i came back again over the runway and back to 40 or 50% of throttle and from far i can hear the same, like it wants to quite so i idled back to land and here we go on a dead stick landing.

i'm not sure whats happening here, i got the engine new broke it in nicely and had a perfect one year flying on that engine, i like the power and how reliable & economic it used to be...

If any one can help on that matter since i cant figure out why it does this only on the mid range of throttle
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Old Feb 19, 2012, 10:23 AM
Oxford Panic
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United Kingdom, Oxford
Joined Feb 2003
3,655 Posts
RedFox,

It may not have anything to do with the re-build if you put the carb back together correctly. Try changing the plug, some Saitos need a Saito brand plug to run properly.

A.
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Old Feb 20, 2012, 02:09 AM
Reactor G/P 3D Saito 82a
Joined Jun 2010
81 Posts
Quote:
Originally Posted by AndyOne View Post
RedFox,

It may not have anything to do with the re-build if you put the carb back together correctly. Try changing the plug, some Saitos need a Saito brand plug to run properly.

A.
Thanks Andy, but I'm ruining my engine with a Saito Plug and it's new as well, yesterday i tweaked the needles again trying to get it run properly but now a new thing came up, if i held the throttle at any point from Idle to like 80% it doesn't hold the RPM like before instead it keeps on picking up and then dropping and then picking up then dropping again continuously the RPM !! it's really confusing i loved this engine and how it used to run reliably, any ideas ?

For the carb it's only 2 screws that i took out to reinstall the o'ring on the intake pipe and screwed them back again i didn't open the carb barrel or anything
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Old Feb 20, 2012, 07:36 AM
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I TOBOR's Avatar
Joined Feb 2007
2,769 Posts
DJ, when you tweak the needles you gotta have a plan, Make sure the LS needle is too rich which it sounds like it already is. Peak the HS needle to absolute peak and leave it peaked, now set the LS needle for the best idle and transition and be willing to sacrifice a little idle quality in favor of the best transition. The LS needle controls the mixture for about 85% of the throttle so it has a huge effect on fuel economy or the lack of it. Go for 2,000 rpm idle and then fly it at about 2,200 idle on the ground. Set the HS needle at your usual setting after happy with the LS. Don't be tempted to set the LS with the HS set 300 rpm rich, you'll end up trying to compensate for that extra richness with the LS needle and end up chasing the needles back and forth forever.
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Old Feb 20, 2012, 08:02 AM
Oxford Panic
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United Kingdom, Oxford
Joined Feb 2003
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Redfoxx,

Are you sure you didn't loose the conical spring that holds the barrel to prevent backlash. I guess not but this would give these exact symptoms. Or could it be that the carb barrel got bent slightly and is binding not allowing the spring to do it's job.

It seems as if it's down to the carb somehow. There may be lingering dirt in it somewhere. Try running the engine at full throttle then richen the main needle and remove the exhaust pressure line. It will go lean but should keep running which should allow you the richen the main needle to the extent that any dirt may get washed through the now widened gap in the jet.

Failing the above, completely dismantle the carb and wash it out with fuel, or you could the bike pump trick. Get a couple of feet of fuel tube and attach it to a bike pump and the other end to fuel inlet nipple on the carb and with the main needle several turn out try pumping as hard and as quickly as possible to blow the obstruction through.

A.
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Old Feb 20, 2012, 08:13 AM
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DJ, I just picked up that you changed to a wood prop, wood props are generally too light for a fourstroke and require a higher idle speed.
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Old Feb 20, 2012, 08:22 AM
Engine Category Manager - EVO,
United States, IL, Champaign
Joined Aug 2005
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If the intake o-ring was unseated in the original crash I would take a good look at the intake tube. It doesn't take much to bend these slightly and cause an air leak. I'd consider replacing the tube.

Pete
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Old Feb 20, 2012, 11:02 AM
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Adding to Pete's suggestion, if you order the pipe and O rings get this guy too, problem gone.

http://www.horizonhobby.com/products...ab-rr-SAI82B17
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Old Feb 21, 2012, 02:33 AM
Reactor G/P 3D Saito 82a
Joined Jun 2010
81 Posts
thanks to all for your time and support ,

Andy, i'll try your methods this week end and let you know if they worked

Tod: so do u think i should put back my 13X8 master air? will it be heavier and easier to track my needles back ?

i dont think anything is wrong with my Intake pipe but i'll still take a closer look again and check if there is any air leak there
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Old Feb 21, 2012, 02:36 AM
Reactor G/P 3D Saito 82a
Joined Jun 2010
81 Posts
though it's really weird when i hold throttle as i mentioned earlier at any point from idle to about 80% it keeps on picking and dropping RPM, it feels and sounds like the pinch test, like pinshing the fuel line it pikes up rpm for a second or 2 then release the fuel line and it drops back that's how it feels and sounds if this will help
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Old Mar 07, 2012, 07:47 AM
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Joined Jun 2004
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It sounds like you may have a piece of plastic debris from your new tank stuck in the needle valve. Try removing the carb. Take out the high speed needle and remove the throttle barrel then flush it out. I bet you will find a little piece of white plastic in there. Good luck!
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Old Mar 07, 2012, 07:44 PM
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Joined Mar 2012
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Quote:
Originally Posted by DjRedFoxx View Post
at any point from idle to about 80% it keeps on picking and dropping RPM
This symptom typically indicates a slightly lean condition.
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