Dave,

At Christmas time last year, I bought a .63FZ for my new 3d profile airplane. I put it on the airplane and it fired right up on the first flip. At first I was quite impressed with its power and reliability. After about 3/4 of a gallon, it started running rough. I have another .63FZ that I mounted on the same airplane, but everything was the same. It ran fine for a few flights, then it started to act up too. Today I mounted one of them on a test stand, since I saw you say once that sometimes there are issues with running these engines on profiles. It acted the same way as it had been all along. When I start either engine, and then advance the throttle to full, the engine revs up to about 11,400 rpms. When I leave it at full throttle, it slowly looses rpms. After about 30 seconds it is down to about 10,300 rpms. If I put the engine to idle and back to full throttle it goes up to about 10,000 rpms. The transition isn't always good either. Sometimes it is great, but sometimes it takes about 5 seconds for the engine to go from idle to full throttle. Fuel is also leaking out in several places. On both engines, it looks like it is coming out around the joint of the cylinder to the crankcase and out around the pushrod guide tubes.

I am running Byron YS 20/20 fuel, an APC 13x4 wide prop, and an OS F glowplug. I have reset the engine to factory defaults and followed the tuning instructions on the YS website several times, but I haven't gotten it to run well.

I really thank you for your help through this. I know YS engines run great and produce tons of power when they run right, but right now I'm quite disappointed in both of mine.

The key here is that both engines ran fine on the profile at first, then the performance became worse. In our experience, profile aircraft have the tendency to warp the engine crankcase (leaking from the joints in the case), because the nose is not strong enough nor rigid enough to support the engine properly.

I would advise that both engines be sent into service for repair.

Thank you for your reply, but I am quite annoyed at this.[:@] Imo it is very frusterating that YS can't make their engines strong enough to be run on a profile.

Can you tell me where to send my engines and what the approximate turn-around time will be?

Please send them to:


YS Service
1295 Industrial Court
Gardnerville, NV 89410

Phone 775-782-4562


We are running about 7 to 10 days at this point.

I'll try to mail them tomorrow or the next day.

Thanks for your time.

OK

Dave,

I seem to be having the exact same trouble with my ys 63 fz. Awsome engine at first.

I am running one on a top cap profile, with wildcat 20/20 and type f plug with a APC 13-4 wide. my engine doesn't seem to leak fuel though. I just adjusted the valves last night and ran engine tonight. I have a little better power now but it still loses rpm as it is held wide open in a hover, or testing on the ground. Running about the same RPM as above post, 10,300. I feel like I am banging my head against the wall. Is there anything I can try before I send mine in?

Thanks,

WOOD

The weather is hot all over now. Lower the prop load on the engine and let it wind up a little. Bringing the rpm up by 1000 will probably cure the problem.

Try it.