Ok........after 7 flights my engine is still acting up.....(its previous owner ran about 1 gallon prior to me, and I've run just under a gallon)

Tried riching it up, and leaning it out both high and low ends and combos.
Baffled up the motor and it now temps out between 140-170 (depending on the length of flight)


After about 5 mins of good running, the motor sounds like it drops a cylinder at anything above 1/2 throttle. Motor is not yet broken in
But the first 5 mins it runs great with lots of power.

Here's what I think...

1. Plugs are bad
2. Timing is off (but wouldn't that effect the whole flight?)
3. Ignition box is bad (it is raised up 3mm for airflow)
4. Motor is bad

Here's a pic of the plugs. Both of them have carbon build up just above the threads on the plug, on the smooth portion.. Both only have it on half of the plug. They don't appear to be too dark on the spark point. I ordered some new plugs incase, but was wondering some other peoples opinions first. (also what gap should the plugs be?) To me it seems odd to have the carbon build up like it is. But since I've never had a gasser I'd thought I'd ask first.

two things you oil gas mixture is to heavy on the oil. Or you have to much back flow from your exsaust.

First off what motor is it. the plugs look fine. except for the one on the left. it looks like the element is crocked...maybe its just the picture.

How is the air flow into the carb it is restricted.

running 50:1 ashless lawnboy.....Not too heavy


What is backflow on the exhaust? never heard of that?


Its a 3W106 , the Pic is kinda cloudy but neither plug is cracked. Carb is unrestricted.........plus the motor runs fine at full, 1/2, idle until like the 5min mark. So its got something to do with the heat. is it heat on the plug, ignition box, rings, etc. looking for some educated help before I pack it up and send it in to be looked at.

I would call Aircraft Int. and ask them for an opinion. I have the same engine with no problems at all but have found Gerhard very willing to help with minor problems or questions. Worst case, the engine must still be under warranty I would guess so send it to them to get checked out.

Back flow from the exhaust is caused when your outlet pipe is to small or in the case of a weed eater muffler, the baffles inside get built up with so much crud that it seals off your exhaust flow. I rebuilt a weed eater carb once only to discover that the muffler was packed with gunk which limited the rpm of the engine severly at anything past half throttle. I doubt your muffler could be clogged this soon.

are you running a 4.8v or a 6v pack on the ignition??

do you have a velocity stack on your carb??

have you checked your tank setup out?? if the pickup line has come off the tube in the tank, drawing fuel will be difficult.

just a couple things off the top of my head.

tony

Tank is fine.

No velocity stack, but for now I'm not doing 3-D. And the engine noise happens at straight, level, in turns or inverted, doesn't really matter

Ignition battery is a new 2200 Lithium with 6v regulator

As for the pipes, neither of them was cut, I left them stock. They don't appear to be blocked. ( I know they weren't when I installed them. Also the inside of the motor looked fine before installation, as i turned the prop. Didn't look like alot of build up. (had several people look at it).


I am most likely going to try this...........one more run time, with new plugs and the igntion wires swapped.................(as after inspection last nite I only had oil spray from one muffler). If the spray swaps, I'll lean toward igntion box......if it stays.......the whole thing will get packed up and sent in.

with the holidays coming up, I was really trying not to send it in.


ANY ONE KNOW THE CORRECT GAP SETTING ON THE PLUGS?

the DA 100 is .020". i would guess the 3W would be similar??

tony

Check the ignition wiring to the ignition box. The solder connection of one of my lead wires failed from vibration to the ignition box. Engine ran rough and at times would just quit. I chased my tail for weeks and two DS's until I removed the ignition box and found the problem. The wire just slipped out from the connector when I removed the box. Once repaired the engine ran perfect. May not be your problem but worth checking out. I also thought I had a bad ignition box, but it was only the wiring connection.

I talked with Bobby at Cactus and a buddy of mine that had a bad ignition box that I used to fly with. Both said they felt it was the igntion box.


So I sent it in..........And luckily a local guy here in Vegas is going to lend me one of his ignition boxes for the weekend. So with the new plugs I ordered and a new ignition box it should be fine......if not, then we know its the motor. I'll keep everyone posted.