Hey everyone i just purchased the os 50 sx for my GP cap 580. Break in, the motor did great. But then the problems came. They last couple times i ran the motor, the glow plug seems to back itself out causing the motor to loose tune in flight or run up. I`m am using brand new OS A8 plugs tightened to snug. The motor has a bisson pitts muffler if that makes any difference. How can i fix this problem?

Thanks

Interesting--- I suppose you could use the stock muffler to see if the Pitts is doing anything, can't imagine the muffler is the problem though...

What fuel are you using? Also, this may sound silly but are you sure you have the glow-washer on there?

I run OS-8 in my OS-50SX, no problems---

Broke in the motor with the stock muffler, yet the plug came out then too. Yes i put a new ring each time i changed the plug. And i`m running 30% Omega fuel.

Thanks

I was running a Magnum 61 four stroke and I got close to it from the rear to use my Glow Bee tach on it when the plug blew out right past my head.

I had used one of those Dubro Tee wrenches to tighten the plug and it must have bound up against the head?

That was $10 worth of experience for a OS"F"?

Enjoy,

Jim

Derek,


You're using too much nitro.

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REQUIRES: Glow starter, fuel with 5%-15% Nitromethane and 18% oil content,
2.5mm ball wrench to tighten muffler screws (can use GPMR8012).

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This is the [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXALM2&P=RF]Tower web page[/link] for this engine.

When all else fails RTFM...

This may not be causing your immediate problem, but it may destroy your engine, nonetheless, unless you added two head shims to the one already there (not the washer under the plug).

If the new synthetic oil in CoolPower has too much extreme pressure additive, it may prevent your plug and washer from locking on the seat.

I'm running 20% in my 50SX with no obvious problems. I have a couple of friends running 30% who report okay so far. Of course, we are at 5000ft altitude, which may reduce the effective compression.

Greg

Greg,


Altitude does reduce the effective compression ratio.

Although OS break-in instructions have been known to be incorrect at times; contradicted by their own Q&A and people, I would say their nitro recommendation must be adhered to.

They would only gain by recommending more nitro, if it was safe for this engine.

I don't think Cool Power a sufficient percentage of oil either... 17%, where 18 is OS' minimum number.

Derek,
I´m running 2 O.S. 50 SX at 9000 ft altitude with 15% nitro Power Master fuel, both runs perfect, one is giving 12,100 rpm with an APC 13X4W in a H9 Twist 3D.
The other one is giving 13,800 rpm with an APC 12.25 X 3.75 that is mounted in my GP Venus 40.
Both engines are fitted with modified Tower Hobbies mufflers.
Check this thread link:
http://www.rcuniverse.com/forum/Over...2648733/tm.htm
30% nitro will overheat your engine and will cause a lot of detonation, and as a consequence the piston can be melted or the piston pin rod can show early wear.
If you want more speed, try a lower diameter propeller on it.

Regards.

I have two of these beasts. I run cool power 15% nitro with 4 ounces of klotz oil added, per gallon. Both engines love this mix which works out at 18.5% oil, assuming cool power is starting at 16% oil. These are great engines.

Wow! 13.8K on a 12.25x 3.75 - that is impressive...

I would try 15% nitro and see what happens---

He said that was at 9,000 ft altitude?

Enjoy,

Jim

What? Please explain.....

Sincerely
Grasshopper

Yes, 9000 ft altitude, just in the mountains that surround Mexico City (Average altitude in Mexico City is 6780 ft over sea level).

Regards.

Back to Derek's problem.

You are most likely using a fuel with too much nitro. I would recommend you use no more than 15%.
Try it and I think it will solve your problem. Also make sure the glow plug is snugged down good and tight. A gallon of 15% nitro is cheaper than a new engine or new airplane.

Good luck,
doubledee

Brian,


EPA is a compound, specifically zinc dithiophosphate, added to some special lubricants, like camshaft assembly lube, to prevent scuffing and galling between parts, until they wear in, as is the case between a camshaft and its lifters.

There is no real need for this additive in model engines.

But if the lubricant prevents the glow plug from becoming tight on its seat, despite the low thread pitch, I would suspect the existence of this stuff in the fuel.

Hi!
Why the glowplug loosened is probably due the engine got too hot ...due to too much nitro.

Regards!
Jan K

Yes, I know about camshaft lube protecting the parts on initial start up until the engine has been run for 5 minutes at 2000 revs. But suggesting that some of this could stop a plug seating is a bit way out for me. Have you had hands on practical experience with this? Unfortunately I don't have any handy right now or I'd coat the threads and seat and try it out.

Brian,


I guess that would be out on a limb, so to speak.

But I thought maybe someone, out of care for engine longevity, would add this stuff to fuel...



Your assumption; overheating from excessive nitro, is more probable.