Ken Cz

Hi,
I started my OS 200 yesterday after sitting for about a year (properly oiled of course) and it started and ran fine - at first.
Top RPM was good too using my same APC 18-6W prop. Engine is mounted 45deg off vertical (not full inverted) and has a on-board glow system set to shut off just below 1/2 throttle.

Problem: After idling for about 45 seconds or so with no issues I bumped the throttle to full and it really backfired - flames out of carb!
Started it again and had the same result.

Any ideas on what may cause this? Too lean on the low side perhaps - or too rich?

Thanks,
Ken

Campgems

Flames out of the carb?? Than one I haven't seen yet. It might be a good idea to check the valve timing as it is just two screws to remove the cover.

The four strokes will usually backfire if running to lean. I've never noticed the flame, to busy jumping back from the prop spinning without the engine running. It may be that you had it to lean. If it is a new engine, it is a good idea to run a tank or more through at a very rich setting, following the break in instructions. The back fire though usually indicates a to lean condition.

Don

Hobbsy

My Feedback: (102)

My guess is that the intake valve is hanging up and not quite going closed allowing combustion to ignite the mixture in the intake pipe. Simply running it rich may clear it up.

w8ye

My Feedback: (16)

I been trying to make this post for a half hour and to get RCU to work!!!!

In extreme backfire cases from being too lean - they can very well flash out the carb inlet.

The timing is mosty likely OK or the engine wouldn't run correctly at other times

If a valve was sticking it might stick most any time and not just when you give the engine the throttle

The key to this event is that it back fired when he suddenly gave it the throttle.

Hobbsy

My Feedback: (102)

I'm always slow to blame the timing, it can't change unless something catastrophic happens. A lean LS needle could definitely be the culprit caused by a little castor maybe. Has the fuel always been PM all synthetic. Thanks

Campgems

Or someone hashad a peak inside.

Don

Ken Cz

Thanks to Hobbsy, w8ye, and Campgens for you responses.
For sure I will check the valve clearance, adjust the LS needle to richen and see what I get.
I have always used PM all synthetic or Coolpower all syn. Engine was used when I bought it but was run very little and did not have any castor residue.

Now that I have some ideas on what to do it occurs to me that I was running this engine on another Aircraft and using a Perry Pump due to tank location. It also seems ( although it was well over a year+ ago) that I had to lean it out a lot to run correctly with the Perry Vibration pump.

Again, your expertise and guidance is appreciated. Slowly I am learning....

Ken

ton2di

My Feedback: (182)

Ken,

My 200FS was also leaned a little bit more when I installed a vp-20 pump. Make sure you richen the low end needle if not using the pump in this newer plane. I could just imagine a backfire with this size engine and those big props (not very exciting to see).

Tony

Hobbsy

My Feedback: (102)

You're right Don, even some peoples peaks inside are catastrophic. That wouldn't be case with Ken.

Tony, about 10 years ago I had a real exciting backfire with my early high compression Saito 1.50. It back fired and made a brand new Tru-Turn spinner look it had been run over by a truck and about a year later my neighbor found one of the prop blades in his flower garden.

Ken Cz

Hi,
I ran the OS 200 on the test stand again today and richened up the LS until the engine ran smooth, no hesitation, no backfire. I pinched the fuel line closed and the engine continued to run at the same RPM for 5-10 seconds, maybe more, before quitting. Started easily and idled smoothly. Top end very strong and backed off4-5 clicks to the rich side.

I have not checked the tappet clearance yet.

After running the engine for several more minutes it felt very hot to the touch. I took a digital temperature probe and placed down inside the glow plug pocket ( after stopping the engine of course) and it read about 225deg F. I checked at the side of the cyclinder about where the top of the piston come to and I read 230deg. Of course, the engine is mounted on a plane on a test stand with not much air moving over it (Cowl off).

Does this seem too hot for normal under these circumstances? Or should I just go fly it??

Again, I am running a 18x6W prop, Powermaster 15%/20% syn. OBG system.

Rudolph Hart

Hello dave ken raises a good point re temps.Is there a marker pen for temps? that you can use as what i've read about digital point temp gauges is that they are a bit vague about what part of the engine exactly..you are reading.My method has been far less scientific than that so far,if i can hold thumb and forefinger on the rocker covers for more than a second or to without saying h@!y f#$!!! all is good.Your thoughts?

Campgems

Ken. it sounds like you are ready to fly. Keep it close for the first flight and then let out the leash on following flights. The engine that runs best on the bench probably isn't the engine that runs best in th air. If it starts easy, runs strong, idles for a reasonable time then quickly responds to the throttle, I'm not sure what else you could ask for. Go fly.

Don

Ken Cz

Thanks Don-
Per recommendations, I check the tappet clearance. Exhaust valve was right on - Intake valve was tight with .001 clearance so I opened it up to .004 - same as the exhaust.

The engine did not want to quit from overheating and I'm thinking it wll run cooler in the air once it unloads and gets some air over it.
Unless someone tells me the that 225deg. F head temp is way to hot I'm going to fly it!

Ken

Hobbsy

My Feedback: (102)

OF, if you're addressing this Dave I completely don't care about engine temps, they run at whatever they run at. The hottest running engine I ever had was an Enya 1.55, when you shut that thing down it radiated heat like my Harley does sitting at a red light on 100 degree day.

Ken Cz

Hobbsy,
I am to understand then that you agree - just go fly it?
If it overheats and quits along the way then worry about it?
I guess I just 'felt' it was very hot and I was worried about doing more damage (if there already is some internal problem - like bad bearings, shaft bent, etc) by running it but maybe that's not the case.
It did seem to run well and did not quit on me so perhaps it is OK.

Ken

w8ye

My Feedback: (16)

Put your Thermometer in the drawer where it belongs

Rudolph Hart

Phew! am i glad to hear you guys say that

Hobbsy

My Feedback: (102)

Hey OF, as Forest Gump said, "one less thang"

Bax

My Feedback: (11)

A glow engine  being run in airplanes will become  hot enough to cause severe burns.  We've measured a properly-running .40-size 2-stroke engine at 375 degrees F. and it was running perfectly, and would continue to do so as long as we kept fuel in the tank.  You must set the engine by sound and performance.  Reliance upon temperature to set the engine will result in a shortened engine life.

 A tachometer is a better tool to  help you tune the engine than a temp gun or probe.  Just lean to peak RPM and richen it 200-500 RPM, depending upon how conservative you want to be.  Listen to the engine while it's flying.  If the RPM ever sag when at full throttle,  you're going too lean and you must immediately cut the throttle and land to reset the high-speed needle.

Ken Cz

Thanks to all for the help with my O.S. 200 4-stroke!

Ken