YS-45 FS Issues
The RCU search function doesn't work very well with numbers!!! I looked back over the last 20 or so pages and didn't find anything relavent so forgive me if this has been dealt with before. I apologize in advance for the long post.
I am running a YS45 (side exhaust) with the standard muffler and 10% fuel (Omega). I am running a 11 x 6 APC prop and the stock muffler. (I recently bought the engine used and have run it very little) Although the engine is quite old, it was in storage for some time and probably hasn't seen 10 gallons of fuel. Regulator diaphragm and plunger were recently replaced and the regulator gasket seems to be OK. The passages were a bit plugged but cleared out easily. Needle valve is clear of debris and the check valves are in good shape (and installed correctly). Compression seems to be good. Pressure builds to a respectable level in the tank and there are no leaks in the fuel system. Clunk is good as are all of the fuel lines (double checked). Ambient temperature is moderate and I am near sea level. AS far as I can tell, the plug is in good condition and engine behavior did not change appreciably when I tried a different plug. Bearings seem to be smooth and the engine isn't spitting junk so I suspect that bearings are OK even though I haven't taken the engine apart to see for sure. Engine is side-mounted. So much for the background info...
The best I can do with the engine with the above conditions is ~12,000 rpm - is this about right for the combination? (This equates to just about 1.1 HP and I would have expected a bit better - I can do at least as well with a TT 46 Pro)
The engine seems to "Load up" after extended idle (> 20 seconds) and REALLY seems to bog upon acceleration. (It seems to idle fairly reliably at around 2200 RPM.) Won't reach top end in any reasonable period of time unless I pinch the fuel line to get rid of excess fuel or momentarily lean the needle. I started with the regulator screw flush with the housing and have since turned it out a half-turn or more with little improvement. (My understanding is that this will reduce tank pressure and effectively lean the low end.) I was told that it shouldn't have to be far from the "factory" position unless there is a problem.
I tweaked the high-speed needle for max RPM and then richened it a couple of clicks. (Engine seems to be quite sensitive to HS needle) There was some initial surging and then RPMs settled down although further needle tweaking was necessary. Even running (apparently) rich, the engine was getting quite hot; even after just a few minutes. I didn't measure head temperature but it sizzles spit pretty well after shutdown. I would be surprised if the 11 x 6 was overpropping - the previous owner used the 11 x 6 with 5% nitro and he did not report problems. Surging seems to come and go but not too bad. The engine is in an Ace Seamaster and is cowled but essentially the entire head is sitting in the breeze and there is adequate ventilation around the crankcase. I have run this engine very little since I was afraid of doing permanent damage! Behavior is similar at the start of a tank as at the end of the tank which rules out tank/clunk/foaming problems and most general plumbing issues.
I know these things are supposed to sing with the appropriate tuned pipe but I am not interested in ultimate power - just in a reliable sport engine. If this was a cheap engine, I would probably junk it as not worth the trouble but the potential for this one is high so it is worth a little extra effort.
The problems are:
1) Rich low end and poor transition (due to flooding, I think). It doesn't seem to actually stop running but really struggles.
2) Modest surging at WOT
3) Lackluster performance
4) Running too hot
Questions:
1) Prop choice OK?
2) Would 15% fuel make an appreciable improvement in overheating, surging, low speed richness or power?
3) Is there some "magic" plug that will bring this thing to life?
4) Am I missing something in the engine setup or adjustment?
5) Anything else I should check?
Thanks in advance
Ross