RE: YS 45 FR a good engine?
The YS 45 RE is a very good engine! Since it’s a new in box engine you should bench run it with a 9X7 prop for brake-in. Run it full throttle but rich two stroke, nice smoke trail. Get it up to speed soon, prolonged running cold, rich and slow could hurt it. 15% nitro fuel with always some caster in its oil makeup.
The #1250 pipe may have too much volume. You may not be able to cut the header and pipe short enough to get it tuned for the high RPMs you’ll want for this application.
I use a Macs "fuse top" #3572 header and a muffled tuned pipe #1240 or #1140. The header and the pipe will need to be cut to tuned length 11 5/8" measured from glow plug to large diameter apex on pipe. This measurement is the hypothetical "stretched/strait" length or true distance from glow plug to apex (the high point on the pipe). It will appear shorter with the fuse top header. I use a mini tubing cutter and debur the I.D., make sure the chips don't get in the engine. Both header and pipe need to be cut so that you don't end up with the coupling at the turn on the header. A good engine, broken-in & good bearings should see a minimum of 16,300 on 15% nitro with an APC 9X9 and a good tuned pipe, this is my benchmark. OS#8, Enya #3-#4 or K&B 1-L glow plug life is good and replacement is usually indicated by erratic performance so don't start chasing/changing needle settings if things change.
On 30% nitro with Enya #5 or K&B HP glow plugs expect about 600 more rpm (header/pipe shortened again too). With a marine (nitro) pipe #1349 I have seen 17400 rpm on a APC 9X9. This on a clipped wing Diamond Dust will see an easy 160 to 170 MPH! The high nitro and marine tuned pipe is NOT the way to start out, you will have your hands full with the first pipe recommendation for a while.
The YS engine uses a pressurized system so you will need a fuel tank that wont burst or have the stopper popping out so use a Hayes tank "8 oz reg" P/N 070. Isolate the tank with 1/4'” thick pads of real foam rubber on bottom and sides, don’t pull the restraining strap too tight. Make sure there's room on the sides of the fuel tank, as it pressurizes and grows.
You will need a lot of expo if you use a lot of control surface deflection, but be warned, use low expo at launch or it could get exciting and expensive.
One word of caution, inspect the blades before every flight, look for white marks on the blades near the hub, if seen discard the prop immediately, this engine has thrown blades!
I’ve tried the gamut of pylon props and some do go a bit faster but they are much slower than the sport prop to get back to speed after a hard maneuver. The pylon tips get messed up easier in landing, handling, transport and storage too. Don’t forget to set the prop horizontal as it comes up on compression so it wont snag a blade on landing.
The high speed needle ratchet clip has a tendency to break or weaken. If it happens, just remove it and slide a large silicone fuel line over both the needle and needle housing. This is needed on Webra 55s too. Put a file mark on the needle thimble so you can tell if the needle setting is changing after a flight.
Like the YS 4 strokes, the 45 uses a pressurized system and needs some special attention that isn’t mentioned in the instructions.
To fill or drain the tank you need to vent the tank between the check valve and tank, than fill between the filter and tank. Reconnect both lines as before when done.
Don't put your finger over the carb to prime, the diaphragm in the pump could be damaged.
Use only YS after-run oil, other oils could damage the diaphragm and seals in the pump.
To make my bearings last longer on all my engines, I pump out the flight fuel, add a few oz. of FAI fuel (0% nitro), run it for a half a minute or so (it will run rich), pump out the fuel than run it dry. Your done!
Hope this helps.