G'Day Crew,

I decided to start running in my brand new OS 52FS today. I am using 10% nitro with 20% SYNTHETIC oil ONLY. IS this ok? Or should I use some castor in it while running in.

The fact is I ran two 8oz tanks through it already, alternating 5 seconds lean and 10 seconds rich. The burnt fuel/oil that has come out of the engine is very dark almost black and the glow plug was very oily and very dark.

Have I damaged the engine already? My tach was indicating 15,100 rpm with a wooden 11x6 prop.

Thanks for your help.


Regards,


Rob

Fuel should be fine (If you look around, there's many discussions on which fuel formula to use, each diffrent from each other . I run 15% nitro with synthetic/castor mixed fuel, other run straight synthetic and like this better....(But yes, some added castor for break in is probably a great idea)

Your engine is serioulsy overspeeding at those high revs.
Normal speed range for a .52 and a 12X6 prop should be around 9000-11.000rpm, not much more. If you're seeing that high rpm (15k+) you need to restrict it by propping the engine harder = more resistance = lower rpm.
I run 12X6 props on my .52 fourstroke engines.


Try a 12X6 prop and go easy on that engine during break in.
After break in, slowly adjust the high speed needle to maximum rpm and then back off -500rpm from the top.
When flying, you should see a white smoke trail, indicating a nice, rich setting and the engine will go and go and go and go and....

737, follow Test's advice on the rpm range - a 12x6 APC is a good place to start.

Also, check the exhaust system and ensure that the locknuts on the exhaust port and muffler are nice and tight. Dark, metallic oil is often a sign of loose exhaust componentry. A four-stroke's exhaust output "spooge" with full synthetic oil should be pretty clear, perhaps with a tinge of brown when run hard.

We'd check your tach. We don't think that engine can run at 15,100 RPM. It should be getting valve float long before that. Were you using an optical tach and had artificial light present?

We only get into the 10's with an 12 x 6 prop. Dropping down to an 11 x 6 would not gain over 4,000 RPM. Something's off, here.

Gentleman, many thanks for your replies.

I might put some castor in my fuel for the next couple of tanks and see how it goes. Cant hurt.

I will by a 12x6 prop and run that. I will also recheck the tacho. Hopefully I havent done the engine any damage.

Thank you all again for your time and responses.

Regards,



Rob

You should never run without Castor. If you want your engine to last long, you need to always run fuel that has some castor in it. The synthetic oil does not have enough film streingth and will allow metal to metal contact at high pressures. Im very disspointed to see people giving you bad advice. Synthetics in model fuels are just not up to the job, and many manufacturers specifically recommend castor in their engines. I would not run any of my engines without castor in the fuel. Just buy fuel with castor in it, its easy.


15,000 is way to much RPM for a 4 storke, the book will say around 11 and change max. Use an APC prop, wood props are to thick, and do not have good airfoil sections due to limitations building with wood, and very inefficient compared to the APC. Much of your power is being wasted when using wood. The rest of the world stopped using wood props in the 1930's, its time for the modeling world to figure it out.

Regardless of what a propeller is made of, you select a prop that flies the airplane the way you want it. Wood is as good a material as any. It depends upon the maker. There are some fine wood props out there for models.

Some of the finest propellers for light aircraft are made of wood...always have been. There are some advantages to wood, and some disadvantages. As long as you know what you're going with, they're fine.

Just plain not true. It is VERY RARE to see any wood props made anymore on real aircraft. Just to an airport and see how many wooden props you see on the flight line. For modern aircraft where efficiency is importnat, carbon fiber props are the best choice.

Model airplanes are so overpowered, and efficiency is not required to make the plane fly great, so wood works even though it is inefficient. Many people just measure RPM which does not tell you anything. It is possible to get lots of RPM with very little thrust. I stopped using wood after running tests with switching between wood and the APC prop on the same plane. Speed, acceleration, and rate of climb were improved noticeably when using the Composite prop.