mesaflyer

OK I need some help. This is my first gasser. The engine is out front with no cowl. The engine ran almost flawless for the first three gallons of 24:1 gas. The needles were set at 1 ½ for high and 1 1/3 for low when I first started. Awhile back, one of the guys at the club suggested that I lean the low end just a bit because at low speed it was kinda surging. That didn’t seem to change much, if any, but the engine still ran good (other than the surging). After three gallons, I switched to 32:1, and it ran even better. The engine just kept getting stronger. Now, after a total of about 3 ½ gallons, I was flying along about 5-6 minutes into the flight and when I cut the throttle, it died. Got it on the ground, couldn’t find anything wrong. Filled it back up, and a few minutes into the next flight I cut throttle and it died again. I decided to bring it home and check everything out.
Fuel lines, clunk, battery (4.8v, 2000mAh), etc all look good. The spark plug looks pretty good and I cleaned and set the gap at .022”, which is where it was. Checked the spark and it looks good. Pulled the carb end plates off, and everything looks normal to me. (I have a little experience with motorcycle carbs, but I realize this is not the same thing) Put everything back together, charged the battery, and started it up. I have been flip starting without much of a problem, but now it takes a few extra flips. When it starts, it runs great at full throttle, but when I try to back down the throttle getting close to idle, it sounds like it misses a beat, or skips a beat. I have adjusted the carb so that I can get it to run good at full throttle, and sometimes it runs at idle for 10-20 seconds, and then quits. But most of the time, it just dies at low speed as I am lowering the throttle. Also, it would hesitate when advancing to from idle to full throttle. So if I lean out the low end just a little, it stops the hesitation. But then when I start to cut the throttle (from full throttle), it usually dies, or idles for a few seconds, and then dies. To me it sounds like the carb has issues. I have no idea how long a carb lasts before it needs new gaskets or rebuilt or replaced. So, do you guys have any suggestions?

nobodytwo

Mesa:

Open your low end (the inside needle) 1/8 of a turn. You are running too lean around idle.

Happy Landings!

mesaflyer

Thanks for the response, but I tried that. Adjusted it both ways just for kicks, a little at a time 1/8, 1/16, it just keeps cutting out. I even adjusted it too far rich and tried to bring it back. Same result.
After reading a little more on here, I'm beginning to think maybe it's electrical. Going to try a new plug next. I'll post my results.

Planeclothes

My Feedback: (1)

It does not sound electric to me. Check the carb inside (filter, etc.) make sure it is clean. Don't forget that high and low needles interact, every time you adjust one you have to re-adjust the other. Try this link to see if it helps in any way:
http://www.rcaer.com/pages/files/RC%...0Technique.pdf

Good luck.

mesaflyer

Thanks for the link. Looks like some good advice. I e-mailed Jody at Valley View, and he sent me some things to do. I'm taking some time off, so can't get to the plane for a few days. I'll post what I did to get it running right again, I hope.

mesaflyer

Update:
After several very helpful e-mails with Jody from Valley View RC, my engine is running great.
This is his first e-mail to me with a laundry list of things to:
Hi Pete,

The first problem you have is to much oil, I don't know what brand you're using but for most anything available in the US, unless you're running full tilt almost all the time 24:1 is a lot of oil, you may have used up your spark plug, 32:1 is the max you would ever need even for break-in. I know what the "manual" says but they don't have many of the same products available to them in China that we do here. The oil I think is just exacerbating the real problem, it sounds to me like you have an air leak, the surging is a classic symptom. The most common place on that engine for this to happen is between the cylinder and the insulator (the black plastic piece between the carb and cylinder), especially if you had taken the carb off and reinstalled it. Many times people over tighten the carburetor bolts, this can cause the end of the bolts to protrude through the insulator and push it off the cylinder causing an air leak or the insulator to crack/break. The cylinder side of the insulator is almost never flat and barely seals at best, if it's not cracked from over tightened carb bolts remove it and surface the cylinder side of it with a sanding block and some 120 or 150 grit sand paper until it's flat then reinstall it. Before you put the carb back on cut 1/8" off the end of the carb bolts, that way you won't have to worry about them going all the way through the insulator and messing up your nice work on the insulator. Check your ignition timing and set it at 28 degrees BTDC with a degree wheel, they are notorious for being way off and this can make them hard to start and not idle well. Replace the spark plug with an NGK CMR7H, get some fresh 40 or 50:1 fuel mix, start it up and tune your carb. Don't run it rich, tune the high needle for peak RPM and the low needle for the leanest best transition then just a smidge richer. I have never used an electric starter on a gas engine, if things are right and you learn what it likes they will start pretty easy by hand flipping. Let me know if you have any other questions. Good luck!

Regards,

Jody Haack 27e

Valley View RC


After doing everything listed above, with the exception of changing the plug (had an extra Torch plug, will switch to NGK next time), the engine ran ugly for a few minutes and then quit. I turned the engine over slowly, and it turned out that it was sparking at the sensor, instead of the plug. Not good.
The company I bought the engine from last year is out of business, so much to my surprise, Jody sent me a new ignition under warranty!
After installing the new ignition, and doing the items listed above, the engine runs great. Better than it ever has.
Can't wait to get the plane in the air this weekend.
I attached a couple pics of my plane (Four Star 120) that one of our club members sent me, before I had engine problems.

jedijody

My Feedback: (1)

Nice work Pete!

mesaflyer

Thanks Jody.

And thanks again for all your help. VERY much appreciated.



This plane flies soooo good, it's just a blast to fly.