Four Stroker - This is a reach out for help. First of all, you need to know how I "inherited" this problem with my YS FZ63.
Year 2006 - I saw a friend of mine fly a Pilot Seduction Freestyle and he had a YS63 in it. The plane was fabulous but the engine was occasionally fabulous...but when it was fabulous, it was fabulous with a capital F.
Back then, (I started this hobby in 2003 with a 30 size Raptor helicopter and then transitioned into planes) I was only flying 2 strokes : TT, OS, Rossi, Webra...45 to 60 class.
I had an opportunity to visit Singapore Hobby that same year and got myself a Pilot Seduction kit too and a second hand YS63 at half price off new (I had wanted a new one but the gentleman in the shop offered me this unit which apparently was run but never flown because the original buyer couldn't get it to run consistently. It was sent back (through SH) to YS Japan and after they returned it repaired, rectified or serviced etc, the original owner had long moved on to OS and didn't want the YS any longer. Whether it was a wise decision, then and now, is a whole different conversation...let's just steer clear of that topic for now)
I started building the kit and I had only managed to finish the wings when I had to move due to work....plus life happened. The engine was left as is in the original box (un-tested) and believe it or not the engine(s) and kits(s) actually followed me to all my work locations but were NEVER unpacked.
Year 2022 - I moved to Qatar (also for work) and I happened to visit (by chance) their RC Flying site - seriously this is probably among the best dedicated RC flying site I have ever seen. So.....all that interest came back in a rush...and I unpacked my kits/engines.
I have started back on building the plane and in preparation I thought it will be best to check out the engine as well....
Last weekend I built a "running in" stand - quick conversation of an old coffee table - and bought fuel, glow, batteries and installed engine test mount to run the YS63. Fuel is 20/18 full synthetic, APC 12x7. What happened next is still a miracle to me....
I primed the engine as per the manual, plus guidance from advice, comments and post in this forum (I did a bit of reading up - I had to), put on the glow starter and turned it with a starter - the damn thing fired up at the first kick.....after 17 long years in hibernation !!! I didnt even change the plug...it's still on the standard YS plug that came when I bought it.
Now as for the engine - after the initial period of idle for 30 seconds to build tank pressure - it idles great, revs up like anything for the first 3 or 4 throttle punch ups.....then after that it kind of leans out and if I don't return it to idle, the engine will cut out. I restarted and it did exactly the same thing three times. I managed to tach it just once - tach was showing 10800 max rev.
I dont see any leaks in the line or tank, and yes the tank is pressurised and I also dont see any bubbles in the fuel line.
Reason I am writing this is because I know this engine isn't that far off from being perfect and the last thing I want to do is fiddling things I shouldn't. What do you think is causing it to lean out after 2 or 3 full throttle openings?
Thanks in advance.