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HelicopterEngines Plugs Mufflers Fuel › Magic for the OS-50
09-08-2003 02:58 AM  14 years agoPost 1
AugustorrElite Veteran - US - My Posts: All  Forum  Topic

ATTENTION: POSTED ON 2003 !!!

That's what Richard Felkins performed on my OS-50 carburetor today, what I would only describe as a magical mod. After he was done with it I had an incredibly powerful OS-50 that runs super smooth.

As most people know, if you adjust the needle of the OS-50 for max power then the idle and midrange lean quite a bit so to prevent over-heating during hover people are forced to run them rich. To solve that issue some people resort to getting the three needle carb to fix that problem and it's still not as good.

After realizing that Richard is runing his old OS-91 engines very smooth, powerful and consistent I asked how he got to make them run like that. He explained to me a simple modification that he learned on his 91 carbs so now his old OS-91 engines (non C-Spec) run like a dream.

I asked him if it would work on my OS-50 and if he would be willing to do it for me and he said sure. So we took the carb off my OS-50 from my EVO and in about 15 minutes I had what I can only describe as a magical transformation of a nice engine into a power monster that runs consistently.

After the mod I was able to lean it 7 clicks on the high end with its resulting tremendous increase in power. The mod works so well that I got to the point that I even had to lean the idle needle now!

I documented it while Richard was doing the mod so I could post it here so here it is:

OS-50 Cateye mod

Disassembling the carb is very simple. Just take the screw that holds the barrel in place off and slide the carb barrel off.

The trick is in that extra piece at the end of the barrel. It has a cateye dosifier. The cateye dosifier works by presenting a variable size opening that depends on the rotation of the carb barrel. It goes from a full open in the center to a minimum opening on the lower side during idle.

The mod consists on opening the lower section so that more fuel is allowed to flow during idle and midrange.

This is the high end side.

Notice that the edge and opening is the original one. No modification to this side is necesary.

This is the idle side.

Notice how the edges have been filed to make it a bit wider.

Here you can see the filed area from the edge

To make it easier to understand here's a diagram of the original cateye opening:

And here's a diagram of the modification:


The gray areas are the ares opened by filing.

This is the file we used:

It's just a standard triangular file.

The cateye bar is assembled again into the barrel ready for re-installation:

I hope I could describe how big the improvement is. Being able to lean 7 clicks feels like putting a much larger engine on it.

WARNING: This mod is not for the impatient. You need to go slowly and try it a few times before you get it right. If you overdo it you'll end up with an engine with too rich an idle or mid and you'll need to get a new cateye bar.

Thanks to Richard Felkins for sharing that knowledge with me.

Enjoy.

Augusto.

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09-08-2003 03:22 AM  14 years agoPost 2
HelicopterJohn

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Seffner, Florida (Just East of Tampa, Florida)

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Engineering break through

Augusto

My thanks to Richard Felkins and yourself for sharing this information. I sounds reasonable. I will have to try it on my OS50 engines.

P.S. Did it help the fuel economy? 7 clicks should help.

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09-08-2003 03:31 AM  14 years agoPost 3
irq

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San Diego, CA

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If/when I get a Evo 50 setup, I'll be doing this Augusto, have you given any thought to the rear bearing problems some people are having with the OS-50?

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09-08-2003 03:57 AM  14 years agoPost 4
Augusto

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Dan,

Not really. I've had my two 50's for a long time and never had a problem with the bearing. What's the problem?


Augusto.

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09-08-2003 04:00 AM  14 years agoPost 5
Airman98

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Southern Illinois

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Sounds like a great mod I will have to try. Thanks for taking the time to post the pictures and diagrams.
Tim

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09-08-2003 04:03 AM  14 years agoPost 6
rtrickyjr

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Drumore, PA (SW of Quarryville)

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Mod

Very kind of you to take the time and trouble to post the info, pictures, and diagrams of the mod. Any touble telling which is the right slot to file?


-Rick-

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09-08-2003 04:04 AM  14 years agoPost 7
Greg McFadden

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Richland, WA

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quite a few of us are going through stock rear bearings faster than we burn fuel. Some people are running ceramic bearings and are having better bearing life luck, but some of us are also of the opinion that the webbing contributes to the problems... There seems to be two different types of rear bearing failure that I have seen.

1> rusted rear bearing.

2> premature wear on rear bearing when running higher nitro 30% fuel. (accentuated greatly on a local heli that is a drag racer run on 50%, he seems to wear out the races before the ceramic balls... in fact he just buys a new ordinary bearing and puts the ceramic balls in it.)

at least those are the two that I am familiar with.

-Greg

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09-08-2003 04:11 AM  14 years agoPost 8
Augusto

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US

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I wonder if all that has to do with the engines runing lean when trying to get power out of them.


rtrickyjr,

No it was easy to tell. It was the side of the cateye that presents itself in front of the fuel hole when you close the barrel as during idle.

It's the bottom side when the o-ring is on the right.

Augusto.

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09-08-2003 04:12 AM  14 years agoPost 9
Beezer

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Ontario, Canada

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I will have to give this I try also.
How do know when you removed the right amount of material?

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09-08-2003 04:16 AM  14 years agoPost 10
fitenfyr

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Port Orchard, Washington

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Hmmm...

Extra carb and a triangle file at hand....

Jason Stiffey
Fly Fast....Live Slow...

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09-08-2003 04:17 AM  14 years agoPost 11
rtrickyjr

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Drumore, PA (SW of Quarryville)

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Augusto

Thank you very much, I'm gonna try it, too


-Rick-

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09-08-2003 04:18 AM  14 years agoPost 12
Indrid

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Hamburg, NY

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very interesting read augusto, all of your informative posts never cease to impress me.

i hereby vote augusto as our "runryder research god".

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09-08-2003 05:03 AM  14 years agoPost 13
reefguy

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palmdale california

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carb mod

has anyone tried this for 61wc engine, since its the same carb, it would figured better performance, right? or is this mod only pertaining to the os50?

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09-08-2003 05:04 AM  14 years agoPost 14
Augusto

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So far the old OS 91 and the OS-50
The principle should work on any carb with the same system and problem.

Augusto.

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09-08-2003 05:11 AM  14 years agoPost 15
Greg McFadden

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Richland, WA

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RE: the rear bearings

I doubt it has anything to do with (at least with the corrosion) the engine being run hot, in fact, I had the worst problems with it when I ran the engine too rich.

The local guy who runs 50% took a look at the races and balls under a microscope and found dents left from his power stroke in the race (or something like that, I don't think he is on Runryder, unfortunatly, and I just moved 1500 miles away ) All I can repeat of his opinion was that the bearing was just too small for the power he was getting out of the engine. May or may not be right (this seems to be the failure of the second type)

I really would like to find the problem... I grow weary of replacing bearings...


-Greg

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09-08-2003 05:23 AM  14 years agoPost 16
Augusto

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I would have to see one.
Is there anyone in my area that has a failed one that I could look at?

Augusto.

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09-08-2003 05:47 AM  14 years agoPost 17
sincity

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Pasco, WA

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Augusto,

Ole Wild Bill from this area is who Greg is refering to. I'll see if I can get one of the failed bearings and post a pic of it in a couple of weeks. I'll be heading to a fun fly this weekend so I won't see him for at least two weeks.

I'll post the pic as soon as I can.

Shawn

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09-08-2003 06:16 AM  14 years agoPost 18
Naomi

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Ontario, Canada

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OS50 Rattle..

Possibly of bad bearing with video link
http://runryder.com/helicopter/t60822p1/

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09-08-2003 06:32 AM  14 years agoPost 19
IsaaX

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Cerritos, CA

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Augusto

Hiroshi at our field just replaced his rear bearing. I think he still has it.

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09-08-2003 06:35 AM  14 years agoPost 20
Augusto

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US

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Isaac,

Can you send it to me?
I want to analyze it.

Augusto.

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HelicopterEngines Plugs Mufflers Fuel › Magic for the OS-50
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