NoFlaps

My Feedback: (131)

I bought an RCG 50cc engine from HobbyKing about a year ago and have out maybe 1/4 to 1/2 tank of gas in her oil mixture is between 40 & 50:1.
I finally got around to maidening her yesterday and I thought the engine sounded terrible!
I don't recall it sounding this bad when I tested it- but I thought- maybe it's because I always tested it without the cowling. With the cowling on oit seems to amplify some metal clanking sound.
It sounds like metal banging- like a chainsaw or something- In flight it is washed out from the high RPM & the distance, but within 40 feet- it sounds to me like parts are coming off or that she's gonna blow.
The engine is an RCG50cc (I've had good luck with RCG in the past- so it seemed like a no brainer):

http://www.hobbyking.com/hobbyking/s...dProduct=19802

I probably should not have flown her with the sound as it was- but my foolish nature prevailed- luckily I got her back with no damage to the plane.
Anyway-
A buddy of mine videotaped the maiden flight (80" ESM T-28) -Flies like a *****cat BTW.

...So have a watch and listen to the end (really apparent at the 4 minute mark- & sounds horrible to me for the next 29 seconds) where she's taxing back and you can hear how load the clanking / banging sound is.
Any thoughts or suggestions would be most appreciated.

http://www.youtube.com/watch?v=cj58W...Qx-vFQ&index=1

I'm dying to fly her again, but I've just not heard a sound like this before.

Thanks in Advance for any help!

-noflaps

pe reivers

Your engine is alarmingly rich on the low end. Tune it, and see how it goes.
Threads on carb tuning, do a search here.
Also, check your ignition timing, and spark plug. The original plug is still in there? toss it. Set timing between 26° and 28°, and set spark plug gap to 0.6mm, which should get rid of the misses if the ignition is any good. Better still, use iridium tipped plugs, set at 0.65mm gap.
You took your chances with Hobby-King, now make the best of it.

Steve Percifield

My Feedback: (14)

I agree on the way rich comment. But i would guess your muffler has also come loose. check it for tightness.

builttocrash

Muffler is tight. After landing we looked it over. Nothing loose that the eye could see. Could the timing cause the "loose metal" sound? Kinda sounds like the connecting rod has too much slop either to the crank or the piston. Could that be the sound?

Live Wire

Take your muffler off and turn the engine over and look at the piston skirt, see if there are any marks on the skirt[:@]

I forgot to say! if it was a rod you probably would have had it go out by now. A scored piston and liner will make the noise.

NoFlaps

My Feedback: (131)

Thanks fellas ...ill check it out and see what I can see. Everything is still tight as a drum regarding parts- but ill inspect the ring for sure.

NoFlaps

My Feedback: (131)

Thank you pe reivers !!

jetmech05

can you move the prop back and forth and feel slop before the piston moves. any greater than 1/8 th of an inch or so and you may have lost the bearing at the crankshaft to the connectiong rod...had a DLE do that to me

Flypaper 2

Was to rich as Pe says. After it's hot, lean out the low end till it hesitates when you open the throttle, Then back it out till you get a good transition. You may have to readjust the high needle as they are interconnected. In other words, when you lean out the bottom end, the top is gradually leaning out too, only by a small amount.

NoFlaps

My Feedback: (131)

Okay, I took off the cowl last night and upon removing the plug and muffler, I could see no scoring on the size of the piston. The plug looked black- but not overly "wet"- this would be due to the richness Re revers astutely pointed out.
I wasn't able to get a pic of the engine interior- due to a baby crying upstairs (fatherly duties called).
However, I did notice a band of oil on the inside of the cowling...This is clearly a new development and clear that it's coming from the joint line of the prop bearing plate and the rest of the engine.
I'm no mechanical genius, but this would suggest to me that oil from the fuel lubricates more than just the engine piston but also the other bearings including the fwd bearings/ ring that are right there where I spec the oil throw (see pic of cowling and black ring of oil). Meaning that it's normal- and maybe it's just more evident given my higher than normal oil content in the fuel.
BUT, as jetmech05 brought up...Is there slop before the piston moves ? Answer: I believe that answer to be YES (I think). Skylineflyer, builttocrash and another club member or two and I all looked at the engine and noticed there was a lil' Lt-Rt rotational slop -maybe 1/16" or so which we commented could be a slight concern. I'll check it out tonite for sure.

pe reivers

Very rich for sure. That plug will almost stop working, it is that fouled.
Play is normal! Without play your engine would seize pretty quickly. When prop tip play approaches 1/8th" it checking up time.

jetmech05

A little play is ok any more than 1/8 th of an in or so could be an issue

NoFlaps

My Feedback: (131)

This may spun like a dumb question...but how does one set the plug gap distances with a recessed plug such as those on our RC engines ?
A torque wrench ?
Some special shaped gap tool?

pe reivers

The earth electrode must be adjusted by bending open, and tapping. You need feeler gauges. A hacksaw blade is 0.6mm thick.
Recessed? No. You have to take the plug out of the engine.

Live Wire

I hope I am reading this right Glow plugs have no adjustment and spark plugs if they are recessed are damaged and are no good. The electrode should be where you can set the gap. It takes a standard feeler gauge to set them.

pe reivers

NoFlaps is pulling our leg. In post #10 he has the plug out.

NoFlaps

My Feedback: (131)

LOL...
Yes, I have the plug out...Just seeing who's paying attention.

OK, I've got iridium plug and set the gap, I've got everything laid out to check TDC and even taking off the head to check for any other signs of wear.
+Fatherly duties make doing it all at once a bit difficult.
The plan is to run her again this wkend after the inspection & updates.
Thanks to all and I'll let you know what happens