MarkHenderson

My Feedback: (12)

I bought a used YS63 here on RCU (not the "S"). It appears to be a low-time, claen motor. I've got it on a YT International Freestyle Rush. The first few times out I had to fool with the adjustments (both needles and regulator a little) to get it to run well (I have a couple of other YS's and am quite familiar with their adjustments). I've got it pretty close now and can enjoy some good flights. I'm running PowerMaster 20/20, OS "F" plug, APC 13x4W and Master Airscrew 13x5, TruTurn spinner. I have 2 remaining problems I'd like to ask you advice on:

1. For the first ~20 seconds after the motor starts it will rev to over 11k which seems appropriate for this fuel/prop combo. I always crank the motor 10+ turns on full throttle prior to starting to pressurize the system. The fuel system is holding pressure well. After that time the revs will sink back to ~10.3 and pretty much stay there for the flight. What would cause this slow-down? I changed the main needle around to see if this was a too lean/too rich condition but doesn't appear to be. I also suspected overheating so I ran without the cowl, with exactly the same results. Now I'm wondering if the motor just isn't completely run-in?? It does seem to be getting better with every flight (I only have a handful of flights on it so far).

2. I intentionally have the idle a little fast while I'm sorting out the motor and the plane. After about 5minutes in the air the motor will quit while idling. I suspect this is just that I need to spend some more time on the LS needle, but provide this info in case it sheds come light on question #1?

Best regards-

Mark

Dave Shadel

The engine is overheating and losing it's fit. Either go to 30% heli fuel or run a smaller prop.

You can try stretching the plug element up out of the cavity about .030" to make it run hotter at idle. The 30% will also help the idling issue.

The problem is that your engine does not have a good hot compression seal to keep the plug hot at idle.

MarkHenderson

My Feedback: (12)

Dave - thanks for the prompt reply. I will try the things you suggest. Is there a fix for the low compression problem (like a new ring, piston, sleeve or something)?

Thanks

Dave Shadel

It might need a whole top end, or might just need a ring. Hard to tell without seeing it. It could also be leaky valves. Lots of things in a four stroke to cause problems.

MarkHenderson

My Feedback: (12)

Dave - many thanks for the help - I will try the plug and fuel as the engine seems to work pretty well - I'll also check valve clearnaces etc. If anything gets worse I'll send it in! Your help on this forum is invaluable!

Dave Shadel

Hope you get it worked out.

Let me know if I can help.

Dave

MarkHenderson

My Feedback: (12)

Dave - just a little follow-up - I checked out the motor carefully, replaced the plug (OS F) and made sure it was tight, also adjusted the tappets (were 0.2mm so set them to 0.1mm). Switched to 30% heli fuel and the motor is running GREAT. I'm getting over 11k on the 13x5 on the ground and good pull in the air.

Many thanks!

Mark

Dave Shadel

Great! Keep us posted.

Good Flying!