juanes1969

Mike:
After flying 2 to 4 times the engine suddenly becomes imposible to start. It ussually starts after fliping the prop with choke on, on the third or fourth flip. However, it fies good for say one sunday, four to six flights, and then the next sunday it will only give two flights and then it wont start. The first time it happened, I took it back home and took the carb out and cleaned it, there was no dirt in it. so I took the spark plug out and there was a little carbon build up on the element. I cleaned it and put everything on the engine again. The engine worked fine for about 8 flights. 6 of them right after the cleanup and the other two just yesterday. After the second flight yesterday, again the engine would not start. What could the problem be?
The engine is on an Aviation models (TOC1) YAK 54, the cowling is baffled so the only opening is where the cilinder is, spinning a Bambula 20x10 at 7260 rpms with a supersonic muffler. NiMh battery for the ignition 4.8volts at 2000mAh.
Any advice on the problem Mike?
Thanks
John

Mike Dooley/RCS

Sounds like the NiMH battery is failing?
Bad fuel? Bad spark plug?
Fuel system problem? Air leak?
7200 on a 20x10 is not very good performance, if you are at sea level.
This is not a typical problem.
Keep me posted.

juanes1969

I´m at 3000 feet above sea level. Should I close the high needle a little. When I first started the engine, it gave me 7460rpms, I just opened the needle because I guessed it was too much. But if it is poor performance at 7200 can i close it then without worriing about heating the engine up too much? will this prevent the spark plug to have carbon build up?
Thanks

juanes1969

Well, I checked the fuel tank and lines and there is nothing wrong there. The spark plug the engine came with I discarded it, because it did not have a resistor, so I changed it for a spare plug I had for my zdz80 which are the same.
It might be the battery, the fuel was fresh and mixed 32:1 for break in. However when I choke the engine, it pops and the when I open the choke the engine fires and burns the fuel that came in, then quits and no matter how much more I flip it, it won´t start.
Any advice Mike?
Thanks
John

juanes1969

Mike:
I checked everything and there seems to be no problem, however I would need to know how much mAh does this engine use when in idle and how much at full throttle. It may be, as you said, that the battery is failling to provide the minimun voltage the ignition needs to work. It is a 2000mAh, NiMh, 4.8 volt battery.
On the rpms, at 3000 feet above sea level, can I close the needle to get more than 7200?
John

juanes1969

is it ok to use a Li-Ion battery at 7.4 volts with a 6 volt regulator for that ignition?
Any comments on my previous questions?
Thanks
John