Hi,
I am a beginner and wondered what are symtoms of an 1-1.5cc engine having suffered and over lean run?
My fuel is 20% cator 10%nitro and I suspect I may have run my Norvel 0.061 a bit lean.

1)Piston - when my Norvel 0.061 was new the piston surface mirror was incredible. Should it stay this way normally? After somne breaking it it seem to have some vertical going micro scratches and is certainly not a perfect mirror any more.

2).I read somewhere that castor will save an engine from an over lean run by forming some residure on the piston when burning from overlean run. How one can tell this actually happened - can one see the residue? Whoud this residue make piston move with more frisction one can feel on the prop when flipping/turning?

3)If the above residue present - how do I go about cleaning it?
<I do understand no sanding allowed <grin>>
Or should it go away after a couple of rich runs? Any hints - tricks here? I think soaking engine in parrafin for about 24 hours helped me once... - is this OK for a glow engine though?

4)What actually happens to the engine after an overlean run - lost of compression/scratched piston - something else?
How can I tell I've had it (or rather my engine).....
Any good sites / pages /books on diagnosing engine problems out there?

Hope these aren't too stupid questions. Thanks in advance!

Loss of compression is the primary concern

Hello!
Burned Castor oil (brown /Black residue) will always build up on piston top and sides and in combustion chamber when using Castor oil. This is perfectly normal.
When you run an engine lean you know that you do it because you HEAR IT! (This is a thing you will learn to recognize by time) And the engine stops or runs erratic.
You could also see that after a lean run the glowplug could be broken.
Never ever run an modelengine lean! This is easy to do when you know how to set an engine but for a novice it could be tough!
One way to get ride of the carbon built up is to run synthetic oil instead of castor....and this i what most sportflyers do nowadays.
Here in Sweden (and I would say all of Europe) 15% Aerosynt 2 or Aerosave from Graupner in Germany or the French brand Motul "micro"is what people use and these oils does not produce any carbon build what so ever (excess carbon on piston is no good). The engines are as new inside after several years running.
And they can stand up to heat as good as castor oil or at least what sportflyers demand of and oil , I'm not taking high-rewing 6,5cc F3D pylonracing engines here.......
As for marks (if they are large 0,1-1mm) on the pistonside...this is bad and tells you that the engine has inhaled some microskopic sand or grit..and this will give less power and the engine will perform less good in all respects.


Regards!
Jan K
Sweden

When an engine is run lean enough to hurt it the signs are little round beads on the inner face of the glow plug & cylinder head
these are melted piston head particles leading to a hole melting
thru the piston crown . Ask some one who races a 2 cycle
motorcycle or go cart to show u one the are quite common in this field.

Thanks 3 Channel -
Could you describe these 'little round beads' a bit more for me, pls?-
1)Color - (black?)
2)Size - (say roughly <0.1 or 0.05 mm diameter?)

Thanks
Segei.

Thanks,
This is a very good hint for the syntetic use for me.

About marks/mirror look - would one expect original mirror finish to stay as good as new if there is no dirt???
Or is it normal for finish to go from extremly clear mirror surface to kind of a bit foggier mirror (still mirror you can look into, but you know - not as perfectly poslished as a good glass mirror but more like a polished bit of metal or tin???

As for marks - thanks I will take the engine apart and clean it before running again, as I suspect this may be the case..Although I can't see were dirt came from as I had muffler on and Norvel has got an air filter on the venturi.

Scully The dangerous deposits are very tiny round beads that look like weld spatter. That is what you used to see race car
tuners looking at plugs with a magnifier for . Cause is lean mixture & or preignition.& comes from the top of the piston melting.

an overlean run if continued, will enlarge the piston to the point that it seizes at four points. Thats what makes the engine slow down at lean run......piston enlarged.
d