My apologies to armody and others for hijacking the other thread. Just wanted to nkon one last thing-

I have just washed (cleaned by dipping in plain alcohol for a couple of days) a very old 55ax. This specific engine has a scuffed piston but the liner seems to be OK. It was out of use for 4-5 months for the same reason. Have got some debris in the alcohol and a slight brown color. But the top of the piston has remained brown in color. The sides are all clear now. The bearings are slightly rusted but they seem to roll ok, no problems earlier with them either, just dead-stick after dead-stick even with this engine which could be due to other reasons. I stopped using it after it crashed a Reactor 46 but plan to use it now on a US40+ kit.

Now having washed the thing, I am going to re-assemble. Just wanted to know if the piston top color is natural or should I keep it immersed for a few more days. I have been mostly using plain castor on this engine with a bit of nitro

I am posting images of the top of the piston, side, head and liner. You can see the scuffing of the piston side very clearly, but trust me it is a lot less bad than it looks. On the liner also there is a bit . Dont think you can see in the pic and it is not seen very easily by eye either

Ameyam

Ameyam soaking in alcohol alone, without heat will not remove old color deposits but you are right the photos do look awful and of course with macro photos will tend to look like a sand paper consitancy on top of the piston, has it actully been eaten away? Also the sleeve is very difficult to see around the ports but is sure looks like its in poor shape agine its difficult with the pictures but it almost looks like peeling on the bottom edge of the ports.

The piston top and the head looks as though something has solid has banged around in the swish band area.

John

I make up a witches brew of alcohol, acetone, break cleaner, carb cleaner then test it to make sure it doesn't pit the engine by using an old throw away LA .40. I strip the engine and put in in a sonic cleaner my wife better never find out I'm using. This is a really old MECOA .46. Don't sweat a little discolor but I make sure I get all the carbon off. If you have a lot of engines, maybe a club project then an old used crock pot and anti freeze is the best way to clean them. There are several threads on how to use the crock pot.

That just looks like some carbon build up on the piston and it cleans off fairly easily. I use a fingernail or bit of plastic to scrape off any lumps then scrub lightly with a used (softened) Scotchbrite pad. I've had pistons looking far worse than that one .

Like I said, it is not that bad. You can see the scuff marks on the piston alright but not on the liner much unless you really look for them. This scuffing happened over a month of non-use at my instructor's place when I was not not flying after a crash. This engine was just sitting in his box of engines. But the engine still ran ok after that for about 3-4 months.

By the way, you cant see the exhaust porting in the photo of the pison side because the liner isint there. I removed the liner for inspection and didnt put it back yet. Will do that after thorough lubrication.

I am thinking I will run the engine regardless. I am including a pic of the bearings here. Didnt take them apart, just looking from the backplate side. Loaded them as from the camera. I couldnt get the o-rings off because the carb screws do not turn, the head is not engaging. So I dont want to use the crockpot/ boiling in soap water method if possible. If the clean-up is good enough, I will simply re-assemble and let the new synthetic fuel clean up the engine?

Ameyam

Looks pretty normal. Photo of my wifes, I mean my sonic cleaner. She wasn't using it and it works out fine for my needs.

A lot of that brown patina is not rust. Burned castor oil looks a lot like rust, so if your bearings are turning smoothly then that's probably all it is. The carbon on your piston and on your head is not a problem. Use a paper towel with some ATF and it will get any actual accumulation off.

I dont have access to ATF so that isint a possibility. But I did keep it in for another day and then ran some used fine sandpaper over just to see. It does clean quite nicely. Just to ensure that I dont leave sandpaper grit in it, I have left it in for another day. Tomorrow, I will force air through the carb holes before I reassemble to ensure that there is no clogging. Then I will oil everything throroughly and re-assemble. Hopefully after that is done, it will be working decently enough to install on a US40 for Sunday. I plan to put one tank through the engine rich before I take to the air just to ensure everything is lubricated, any and all dirt is flushed and I dont have any deadsticks.

I was setting up a Reactor 46 with another 55ax that was also dead-sticking and I just wanted to know how to set the LSN. Firstly I set the LSN to 1.5 turns from the fully closed position with the carb baffle totally closed. I was able to start the engine at this point, especially because it had just run. Just wanted to know how to fine-tune further. I have seen people do this with a pinch test. How does that work?

Ameyam

The pinch test is basically just pinching the fuel line briefly to restrict fuel flow.

Get the engine running at a little above idle...maybe a click or two above idle on your throttle stick.

Generally speaking, if the carb is adjusted lean, then pinching the fuel line will cause the engine to die abruptly. (not good...too lean )

If the mixture is adjusted too rich, then pinching the line will cause the r.p.m. to rise quite a lot, then slowly die. (not good...too rich )

When the carb adj. is properly set...pinching the fuel line for several seconds, will cause the r.p.m. to rise a few hundred r.p.m. before it sounds like it wants to quit running.

Thats what it does- after you pinch it, the engine runs normal for a second or so, then begins to gain rpm and finally begins to act as if its about to die at which point if I let go of the pinch it continues running normally. All this happens in 4 to 5 secs. I did do this at idle, however

Ameyam

Yeah...that sounds like it's adjusted fairly close to where it should be?
Pinch test at idle or just a wee bit above idle...just so that it stays running as you are doing the testing, is what I was getting at.[8D]

Great. The engine on the Reactor was quitting randomly at 50-60% throttle at about 50-60% tank. I blow tested the tubing both inside and outside the tank under water as everyone suggested. Even though there were no leakages, I replaced the tubing anyway. I already tested the idle at home. Cant do any more testing in a appartment. Remaining testing on the field. I will also set myself the target of setting the HSN myself (so far I always got others to do it for me).That way I am more in control of what I am doing. Hope after doing all that research, I will have an engine that doesnt quit randomly.

Next target is to mix my own fuel- will do that before the weekend, so that will be another thing I learn. Setting up the airplane with all the control rods and engine I will learn with my next ARF

Ameyam

I will tell you how my advanced instructor teaches people to tune and engine. When your the student it will make you mad and crazy but you learn. The engine isn't running correctly, he tells you to twist a needle? What needle? Doesn't mater, you only have two. You twist one and it made it worse. Then twist it the other way. That made it better but not right? Then twist the other needle. What way? It doesn't mater. You twist the other needle. It's worse again. Then twist it the other way. After going back and forth like this you will finally figure it out. Your face will be red and your temper will be way up but you learned something. Then he would take you by the hand and start going over the fine points.
He was the engine builder/tuner for a big race team and a YS rep for a long time on the west coast so he knew his stuff. Just had an odd {pissyouoff} way of teaching but once you figured out what the needles do he was great. I don't teach that way but I understand what he was doing.
Sounds like you are very close to the sweet spot. Just very little twists needed. High end first then the low end.

I always had problems with tuning engines, not because I didnt persist with problems (I am known to get stuck into problems for hours on end till they get resolved). Problem is that my instructors never had sufficient time. Guess, when there are 3 or 4 trainees trying to get your time, you cant give sufficient time to anyone. I was (and still am to an extent) too scared to try to twist the needle lest I detune the engine and then he wouldnt have the time to retune it so I wouldnt be able to fly that day. I was also concerned that I may not react correctly to a deadstick and thus either lose the airplane or hurt someone.

Now, both of them arent regular and I dont have much option than to try myself. As a intermediate flier, I am more comfortable and guiding another flier on the field and talking to the more experienced fliers has made me more confident.

Issue with the Reactor's engine is that it randomly cuts off, so more trial&error is require which no one has the time for. I know that this isint supposed to happen but I had similar issues with a 75AX earlier. Incidently, both engines were insufficiently run in due to time shortage. That is one lesson I learnt and applied when I replaced the 75ax with a FS91SII on the same airplane and now it is damn reliable

Ameyam