Hi all.
I have a 26cc DZY engine with an electric ignition.
the engine was ran (brake-in) for a half a galon on the ground and the needles were tuned and set to H-1.5t & L-1.25t.
the engine is mounted on a biplane.
i did the testflight on friday and everything went perfect... the engine worked great and the plane flew great.
on saturday, i went to the field, had two PERFECT flights with the engine... and then the problems started...
fueling up for the third flight, starting the engine, checking for WOT and the revs start to go up and down.
it seens the engine just cant ran at WOT.
just a reminder, the engine worked perfectly before.

after a hour of fiddling with the needles - no go.
at home - i took apart the carb and cleand it really good, there was some dirt in it , especialy in the little mesh filter in the fuel input.

put the engine back together, but the problem wasnt solved - it starts hard and just dont want to run at full (or even half) throttle.

the ignition is powerd by a 2 cell lipo battery with a voltage regulator (5V).
i tried using a fully charged 1000mAh nicad battery - no go.

there is no problems with the fuel lines, the engine gets the fuel directly from the tank (no fueling nipples on the way), the tank is well ventilated.

messing with the niddles just doesnt help...

the engine sounds like its starting to build up revs and then just quits and go back to idle ... and again, and again... all of that without even changing the throttle position.

I really dont know what to do, any help will be appriciated.

Thank you.
Raviv.

Is the ring(s) still 'free' on the piston?

Will it run longer partially choked?

Possible air leak in lines, carb block/gaskets?

Is the hall sensor adjustable on this engine, has it moved?

Chad

The rings are "free".
there is no difference with partial choke.
i checkd all carb's gaskets, they are all new , the engine has a total of only one hour work.
i re-tight the carb's bolts - no go.
the hall sensor is ajustable, it hadnt moved, i tried moving it to see if it will make a difference but it doesnt. i placed it back at its original position.

i really dont know if its an ignition problem or a carburation problem...

Is this your only single cyl gas engine running on EI? If not, perhaps you have another ignition to test to rule that out.

arobatix -
yes, this is the only EI i have, i will borrow another one from a friend to eliminate (or confirm) EI problems.
also, i will re-open the carb and clean it again, wont hurt.

the engine is mounted on a biplane that i designed and built from scratch.
is is absolutly heart breaking not to fly it because of a rebellious engine [] , i only have a total of four flights with this biplane because of the time spent fiddling with the engine.

(how do i upload a picture?)

found it [8D]

Check that you haven't blown a crankcase gasket, I did and it had your symptoms. If you can see the crankcase with it running look for oil flowing from the seam line. Mine started out as small bubbles, the was an oil streak, then it blew out over 1/4 inch at one place and an 1/8 inch at another. I replaced the gasket with Red RTV no problem since that.

Hi.
After a lot of testing, cleanning , connecting, dissasembling and re assambeling - i found the problem.
as arobatix said, i changed the EI and it fired without any problem.
I opend my malfunctioned EI and found that one of the DC filtering capacitor was broken - i guess its because of the vibration.
i will replace the broken capacitor and hope it will solve the problem.
the capacitor is a 220uF/25V electrolytic capacitor, i will replace it with a 300uF/20V Tantalum capacitor.

thank you all for your help.
Raviv.

Hey thanks for letting us know what you found, keep us posted on your 'fix'!

Chad