LearjetMech

Ok guys a little background. I bought an Alpha about month and a half ago. Everything on the aircraft is bone stock with the exception of the throttle linkage at carb, and an Ernst charging jack. The motor has never been off or apart. Glow plug is original, and needle limiters have never been moved. Still have 3 blade prop and flywheel and muffler baffle. I have about 1/3-1/2 gallon on this engine (maybe 10-12 flights). The fuel used is Byron 15% nitro, with 16% oil. This is what the shop recommended when I bought the plane. I went out this afternoon after the wind let up. Once it started I had trouble getting it to transition to full throttle from idle. Now since last time I flew (last weekend), the temp has changed by 20-30 degrees lower. I knew this might affect it, and ended up having to richen the low about an 1/8+, as well as the high speed. Did the typical run up and look for highest rpms and I richen about 2-3 clicks from there. Went flying!! I hardly ever fly full throttle except on T/O, and to climb for loops, etc... I generally lope around and work on basic manuevers. Plane seemed low on power and sounded funny. I brought it in and ended up richening the needle 2 more clicks! Took off again and it seemed fine. After about 10 min of flying I saw that my TX battery was low and came in. I have never noticed this black oil on the plane before on any other flight. It appears it has some metal in it but not 100% sure. I decided that I would get some opinions here and make some phone calls to Horizon before I did anything else. I ALWAYS use after run oil after flying for the day. And I use it properly. I used to race R/C boats and we ran 40-60% nitro. We had to disassemble motors after a days use and flush them with alcohol and then oil and bag them. Now one thing I have always noticed about this engine, is that after putting after run oil in it, the next day it leaks at the crank bearing. Is this normal?? And it has always been hard to get it to shut off after a flight. It just keeps chugging even though carb is closed. I either have to grab the spinner or put finger over pipe exhaust!! ANY info would be appreciated here. The pics are of the black exhaust while still on airplane. There is also one of the rag I used to clean the plane.

LearjetMech

here's two more

w8ye

My Feedback: (16)

It looks as though the last section of your muffler is loose? It's causing all the black stuff.

Enjoy,

Jim

LearjetMech

You know I noticed that too after I took the pics, I repositioned it after the first three flights! But it is tight! but cmon why the black stuff. How would that cause it?

w8ye

My Feedback: (16)

Nic,

You could remove the muffler and run it on the ground to see what color the exhaust is? You could also remove the head and look at the cylinder walls for scoring or tiny scratches. You could just look at the side of the piston while you have the muffler off to see if it has a smooth or rough texture. If you remove the motor and then the back plate you could look at the condition of the rod?

Also I've experienced the same scenario when going out to fly on a cooler day except for the black stuff.

Not shutting off is an indication of an air leak. It's usually right around the carb?

The after run running out the front crank bearing is not that unusual.

Enjoy,

Jim

LearjetMech

I'm wondering if I should call horizon before I disassemble the motor. I'm sure it has some kind of warranty on it, you think?

w8ye

My Feedback: (16)

I'd remove the muffler and look into the exhaust at the piston and run it some without the muffler first.

Sending things back is often a lot of trouble for everyone concerned.

The NT engines around here have held up well and have been good engines.

Enjoy

Jim

LearjetMech

I will pull the muffler off and post some pics of the piston and liner here in a few minutes!!

TLH101

My Feedback: (90)

If the rear portion is loose, the vibration will cause wear between the parts. That mixed with unburned fuel will cause a black residue. Does the same thing when a motor is loose on an aluminium mount.

w8ye

My Feedback: (16)

From my experience, the muffler can be loose up in the air while you are running it and then be tight back on the ground after you get it shut down. My mufflers always came apart and I lost the back section out over the swamp. They never fell off in the pitts.

Enjoy,
Jim

LearjetMech

Hey guys, after closer inspection and removing the muffler from the cylinder, you nailed it on the head. There was no sign of black residue in the EX port and the liner and piston look good. The back half of the muffler is loose and moves side to side a bit. That explains the wierd sound I heard in the air (buzzing). Would this explain reduced performance also. It wasn't really bad but not the same!!

w8ye

My Feedback: (16)

I doubt if it had much effect on performance. The worst case would be that it was so loose as to reduce muffler pressure to the tank and cause the engine to run lean. But I doubt if it was that loose.

Your mixture problems were created by the engine itself cooling off while up there flying in the cooler air.

Enjoy,

Jim

William Robison

My Feedback: (3)

Nic:

When you reassemble the front and rear sections of the muffler put a light coating of RTV on the mating faces. This helps a lot with the tendency to come loose. Also use it on the joint between the muffler and the exhaust stack.

Bill.

ksechler

The loose muffler absolutely would effect the performance. The tank is pressurized by the muffler. If the back of the muffler is loose there will be less back pressure and consequently less pressure in the tank. This will cause the engine to run lean. I had something very similar happen to me.

sledman

My Feedback: (2)

I don't mean to knock Byron fuels here, but the one & only gallon of Byron fuel that I tried had castor oil in it, and it too had a lot of black stuff coming out of both the exhaust, and going through the fuel tank pressure tube. I switched to Power Master full synthetic, and the problem went away. Byron fuels have a good reputation at our airfield, and several flyers there use it with zero complaints. Might give you another avenue to try, anyway. Good luck.

LearjetMech

Guys I would like to thatnk you for all your help and expertise! The muffler was the issue and it is fixed now! I also took out the baffle, and I cant believe the motor actually ran with that thing in there. Its basically a solid plate with a ring of small holes in it. Engine responds awesome now!!! Also ditched the remote needle, because of more chance for air leaks. Again, Thank You!!!
Nikolaus