the Wasp

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Guys, see my photo, remember my other post, whereby I could not find a Header that will work on my ShoeString, well I came up with another idea, it's an odd muffler for a plane but my idea worked out great for me, it got the RPM right were I wanted it to be,

know what Tuned Muffler this is ?? LOL, well it's a 50 size Century Heli Muffler (Silent Power Muffler),, but it ant silent. I had a friend welded up an Adaptor for my OS 61FX, and it works, the Muffler may not be perfectly straight but hey, I didn't weld it LOL,

the engine is the OS 61FX,,, fuel is 20% Magnum Fuel, Plug is the OS #8, the weather was cool, around 66,, I'm getting 13,700 Peak RPM with an APC 11X8 Sport on the 20%, and it's not peaky, BTW the fuel is rather old, some 5 or 6 years old,,

the first time I stated her she was really Lean on the Idle Screw, as I come down from full throttle she was so lean at about 30% 40% Stick she had the "Naa naa naa" sound, so I richen up the Idle 1/8th and she was better but still lean but the sound was not so pronounced,, so I then richen it up again 3/16th and she was so rich she would load up, so I closed it just 1/16, at that she runs but she's not constant, she get Rich and sputters badly around Half Stick as I advance the Throttle,

so note that the Idle Screw is now opened 1/4 turn from the First start up with this Muffler.

BTW, too add, I always had a problem with this engine running ruff around Half Throttle, as I type I am wondering if she needs a new O-Ring on the Idle Screw, but if she was sucking Air around the Idle Screw's O-Ring that would Lean her out, this is where I'm confused ??

another thought, I know a Colder Plug is usually used at Higher RPM on a Plane, but not on Helis that have less Flywheel Load at Spool Up, so I'm wondering if the hotter OS #7 would help burn off more fuel around Half Throttle with this Muffler, what is your thoughts on that ??

as for the High End Needle, once I find the peak RPM how much do I richen her up, I was opening it up a bit more than 1/2 a turn once I found the Peak

so where do I go from here ??

thanks guys !!!
Jim

MJD

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Well, on richening from peak - on a regular can muffler with no boost typically 300-400 rpm off peak, on "tuned mufflers" such as Jett, about 800rpm back will compensate for the rpm boost on resonance. Piped systems need more but it depends on the level of boost/tune of the whole system. 1200-1500 is not unusual. Or 20,000 in the case of FAI speed .15's.

Start rich as you won't know what the unloading in the air will be like first time around. Then sneak up until the flight mixture is strong but not over lean.

the Wasp

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thanks MJD, that was well explained, I had Racing Pipes on my OPS Boat engines back in the 90s, but that was a different thing, never had one on a plane,

as for my Mid Range problem, it's a bit embarrassing to say but it may help fix the problem if I tighten the Carb's mounting screws LOL, after cleaning the carb I didn't tighten the screws,, see, I have a brand-new HB Carb, I believe it's made by Perry, I was going to try it on my OS and when I went to remove the OS carb I found both mounting screws loose, I will run the engine again tomorrow if the weather is good and see if I have fixed my problem, if not I will try the HB carb

thanks big time for the reply
Jim

the Wasp

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MJD,, I'm done done done with my OS 61FX, my new front bearing is leaking with only 2 tanks of fuel run threw it, geezzz,, and I'm not going to take it back apart now, maybe this coming winter, maybe sell it cheap, maybe give it a way, or maybe send it to Old Fart so he will bury it

BTW, it did seam to run better with the Carb Mounting Screw tightened, but that bearing is leaking, I couldn't get it set correctly

thanks again for the help

Jim

aspeed

It is a good thing to come out the front bearing. You know there is lubrication. Good to a point anyway. Some motors have a hole or slot from the front bearing to the carb hole to slurp up the dribbles. That can lead to a higher idle speed in some cases.

the Wasp

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that stuff sure turns ugly once it's used, it made me wonder how much of it get's back to the Crank Case and gets up into the Combustion Chamber (oops there I go wondering again LOL)

Jim

the Wasp

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let me tell you about that Heli muffler, with the APC 11X8 Sport she sound very strong at 13.700, and once I finessed the throttle to get it cleaned out from loading up with fuel she would pull the 11X8 from the bottom straight to full throttle, very unlike a Racing Pipe,, even when I richened her up to 13,000 for simulating "Tuned For Flight" she would pull the 11X8 just as hard from down low,

geezz, now I got myself wanting to change that front bearing,,, again

Jim

aspeed

Well,for the wondering mind, here is an interesting video. He also made a clear head that blew the plug out eventually. There is more slimey oil inside the crankcase than you might think.

the Wasp

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in your video it looks much cleaner than it did coming out of my front bearing

Jim