HI,

I WOULD LIKE TO CONFIRM THE PROPER OPERATING RPM FOR MY NEW ENGINE.

I JUST ACQUIRED A 1/4 SCALE LASER 200 FROM A FRIEND. HE SAID IT WAS NOSE HEAVY WITH A 120 ON IT AND REPLACED IT WITH THE YS91FZ.

THE YS91FZ HAS LESS THAN TWENTY FLIGHTS ON IT SINCE NEW. IT SEEMS TO RUN GREAT.

THE PLANE CAME WITH AN APC 14 X 8 PROP ON IT. I THINK IT SHOULD BE A 15 X 8, SHOULDN'T IT?

THE SPECS SAY THE ENGINE CAN TURN UP TO 13,000 RPM, BUT I HAVE ALWAYS HEARD THAT YOU SHOULD KEEP A FOUR STROKE BELOW 10,000.

THE ENGINE TURNS THE 14 X 8 AT 9600 RPM. I DON'T WANT TO MESS THIS ENGINE UP BY LETTING IT TURN TOO HIGH AN RPM.

SHOULDN'T IT TURN THE 15 X 8 AT ABOUT 8700-8800 RPM AND PERFORM BETTER THAN USING THE 14 X8 WITH A HIGHER RPM???


WHAY SAY YOU??

MANY THANKS IN ADVANCE

JOHN

The 14x8 is too small. Try a 14x10 or 15x8. The ideal rpm range for this engine is 9000 to 9500.

Hi Dave,

With 15% nitro fuel it was only getting 8600 RPM with the 15 X 8 APC prop.

I noticed a fuel leak of some kind after shutting it down, not before, just after it was run. It was cowled, so I couldn't see where it was coming from.

I un-cowled it, pulled the engine off and found several backplate/regulator screws relatively loose. No leaks around the fuel lines but I went a head and replaced all of them in case there was one I couldn;t see. Lo and behold it now makes 9100 RPM with the 15 X 8 prop and 15% nitro.

I adjusted the valves before my first post. So i'm guessing that its doing as good a job as can be expected without going to higher nitro fuel. The plane weighs a little over 9 pounds. At 9100 RPM it should be making a little over 12 pounds of thrust.

Will higher nitro fuel make a four hundred RPM difference in power? I have a case of the 15%, so thats why i'm using it. I'll go to higher nitro if you think I need it.

You're opinion please.

Thanks John

We always recommend YS 20/20 fuel for our engines as they will run better on it. The 15% won't hurt as long as it's 2 stroke fuel, not 4 stroke.
15x8 at 9100 is good on 15%.