flybyme

Anybody running a toc 53mm, I have about 3/4 of gallon thru my engine, and I'm getting aroung 6500 rpm, but on my maiden, as soon as my plane reached about 50 feet off the runway the engine died, I found that I had both needles set at 1 1/4 turn. I had great idle and good transition but it quit on my second attempt also....dead stick landing.....slid on spinner, nose to the pavement, no damage. After opening the high speed needle about an eighth of a turn, I took off again....4 minute flight, it was great, until I made a left turn and....dead stick, cut off again. I am near repairing this tough bird.....I Love It, but I need some guidance on keeping it running. I flipped my reed block and carb probably unneccessarily, but I don't want to flip it back for fear of stripping the threads of the carb bolts. I'm turning a bunny 22x8 prop, at 32:1 fuel ratio, with a good plug, fully charged batteries, and it runs great on the ground, idling and transition. I pulled up some instructions from BCMA and it said to start out with (H) at 2 turns and (L) at 1 3/8 turns, and adjust only between 1/4 turn either way. That didn't work either. This is my first gasser and I'm close, but where should I start with the needles and which way should I go?

Cambo

My Feedback: (2)

Hi flybyme
Try the gas engine forum
http://www.rcuniverse.com/forum/forumid_142/tt.htm
you will have much better luck

wish i could help you, maybe airflow over the carb plate?

goodluck

opjose

Gas engines pump fuel to the carb so muffler pressure is not necessary.

However, I had a similiar occurance as you did with one of my planes.

It turned out that the tubing had contacted the muffler partially melting the vent/pressure line.

This produced good running on the ground, but deadsticks in the air.

Go over your plumbing with a fine tooth comb!

That the engine runs well and transitions well on the ground, points to a plumbing problem. Gas engines rarely change characteristics in the air.

Gray Beard

My Feedback: (-1)

Vent/pressure line?? Never seen one on a gasser. Just wondering? What engine was that?
My Brison 2.4 was doing about the same thing, ran great on the ground but right after take off it went south on me. I fiddled with it for a long time but due to the needle placement I couldn't tune it while it was running, needles very close to the prop. Even with a tach I couldn't find the magic spot so I risked some of my favorite parts and got it running and found my high end was way off. They tune like any other engine, I brought it up to the highest RPM at full throttle then backed off a few hundred then adjusted the low end until it transitioned correctly. That was almost the last time I have ever touched the needles on that engine and it runs great.
I just tried some different props a couple of weeks ago and tuned it with a tach, moved the needles then started it up and took readings until I got it correctly where I wanted it. My have something to do with the engine being broken in now because it was easy this time?
The gas engine forum is really the place to ask. That way you can find people with the same engine to help you out.

Bill Diedrich

Do you have a vent line for the tank, one of my freinds had his
pluged this past weekend and was experiencing the same problems
with his new gasser, his first as well until I pointed out that he had
plugged the vent line, once he took the plug out, engine ran fine.

Bill D.

opjose

All gassers require a vent line to permit pressure equalization of the tank, as fuel is removed by the carb. So it IS a "Vent/Pressure" line, just not in the same sense that we use with glow engines.



Novices often make the same mistake I made, assuming that the Tygon tubing has the same heat resistance capability of silicon...

So even if the vent/pressure line is unplugged, it can become resealed by the heat of the gas engine.