Sergei

Hi,
sorry - a beginner's question - I am in trouble here!

I have a 0.061 Norvel Big Mig RC. It is running fine at the moment but I noticed that every time I fly I have some (very little) grey in the exhaust residue on the fuse []? The grey is only visible where residue accumulated in big drops on the fuse near engine ( layer about say3 mm thick )

I don't have much experience with engines but read somewhere that residue should be clean at all times after break in?

Engine has done about 1-1.5 litre of glow fuel (20% castro 20% nitro). I am still running with 3 shims under the glow head too - so it should not be working very hard. Norvel standard plug. Muffler pressure.
I may have run it a bit lean [&o] by the end of flying (may be 2 times for about a minute) - it was running leaner then at the start an I probably did not open needle enough from max RPM setting - I was opening it by about 30% but most people suggest 1/8 of a turn (45 degrees)?

1)Is this serious? Could it be that engine is simply still running in?

2)Should I take it apart and wash in clean fuel in case there is some dirt in it and this causes grey residue?

3)I did not notice it before (may be it was there) but I can now move prop forward/backward by about 1/2 mm - that is there is a play - is this quit bad/normal - should tell me something?

4)I have a Norvel StartUp CL versions - would I be able to use the carb on it if my RC one dies?

Any help is appreciated.
Sergei
Glasgow.

combatpigg

My Feedback: (3)

I would feel for mechanical slop and tighten all screws. Firmly grab the prop and slowly turn it as you feel for axial play. Take off the head and back plate to inspect the engine as you turn it. There are alot of contact points that are aluminum. I've worn out a few crank cases over the years and galled many piston / liner combos.

ptulmer

My Feedback: (5)

Sergei,
in order:
1- Yes, the engine could still be running in. More on this in a moment!
2- Never hurts to clean your engine. If you see scoring anywhere, clean it again.
3- That is normal. If it was too tight, it wouldn't be able to turn.
4- Yes. The Startup is a c/l version of the BigMig. Same basic engine.

Norvel engines can take quite a beating. Running lean for short periods should not cause major damage. It may shorten the overall life and you already know that it's the wrong condition to fly in, so don't do it again and quit worrying about it. At 1 liter of fuel, most engines are broken in, but sometimes a Norvel will take longer. Sometimes, depending on the original fits, much longer.
You say there is gray stuff in the exhaust residue. Could this simply be burnt castor? I don't remember ever having clean residue. It's always black and grimy. If it was clean, I'd probably get worried and add more castor! Unlike synthetic oil, castor does not burn off and will appear in the exhaust. (and on your arms, shirt, etc.) That's why it's so good for smaller engines. It lubricates better and carries heat away from the engine.

Andrew

Sergei --

Another source of exhaust discoloration is the fit between the muffler and crankcase. Because the muffler is retained by a spring, you can get some movement and wearing. If the muffler is the cause, it is normal and nothing to be disturbed about. Check the boss on the crankcase and the relief in the side of the muffler for any signs of galling. If there is a wear pattern, you have probably located the source.

Also keep an eye on the muffler endcap -- some will rotate while running or even back out. I've had one come completely loose while in flight -- luckily, the spring retained both parts. I usually determine where I want the exhaust to point, then clean and JB weld both parts together.

vicman

My Feedback: (10)

Great post Andrew!

rainedave

My Feedback: (1)

The endcap on my Wasp was spinning and it usually stopped pointing directly into the engine bay - depositing all the spent castor oil right onto my firewall glue joints. It also produced dark gray residue and I 'm with Andrew, I'm almost certain it was from the muffler parts rubbing.

I squeezed the muffler body out of round so that the endcap was a very tight fit. It seems to be working so far. But, JBW is a better long term fix for sure.

David

Sergei

Hi everyone!
Thanks a lot for all the trouble answering me!
I guess I will
1)clean the engine ASAP just in case
2)check the muffler endcap - it did come off once or twice already. As it was after a dead stick rough landings I actually thought that the end cap came of from the landing shock.... I gues it could have been other wy round now - that is cap came off and engine stalled as muffler pressure disappeared!!! Thanks for that one.
3)WIll have a look at the muffler to cranck contact too...

CP wrote: Sorry - don't quit get what you mean by "feel" for axial play -is this before I take engine apart? Do I feel for any difficulty rotating the prop? Kind of rough points? Or is it rather that take engine apart first and then rotate as described and see if I can feel any point of contact with the body? Thanks!

Thanks again! really appreciated!
Sergei.

combatpigg

My Feedback: (3)

Sergei, axial play is a term to describe wobble, [not to be confused with end play]. The crank should have no signs of it as you forcefully rotate it.
If you hold the palm of your hand behind a running engines' exhaust stream for, [I don't know].........10 seconds and examine the residue, there should be no signs of sloughed off metal or aluminum grit! A honey color is what you are looking for.
It is a good idea to tightly safety wire the muffler to the case, it might even make crankcase pressure more consistant..