rightflyer

This si my first Ys and I love it, but have a question. I probably have a gallon thru it. It seems to be running far too rich with around 9600rpms, but when I attempt to lean it, the rpms fall off quickly. Does it need more breakin?

Richard L.

My Feedback: (24)

Are you sure you are not on the lean side already? You should be able to attain 11k+ rpm after a gallon of fuel.

blvdbuzzard

What prop, fuel, and glow plug???

Mine was broken in after 4 or 5 tanks of fuel.


Dru.

azhar

My Feedback: (19)

Right flyer,

The YS will look like its rich even when it is too lean. And it sounds like you are very lean. You should use a tach to get to peak and back off a couple 100 rpms. The 11K is achievable with the right prop. What prop are you using? The brand of prop can sometimes make a significant difference in the rpm you achieve.

Azhar

rightflyer

I am using YS 20/20 fuel with a OS F plug. The prop I use is typicall an APC 13x7. I also recently started using a 13x7 Pro-Zinger.

DarZeelon

RightFlyer,

I believe you are over-propping your engine.

Please read this web page:

http://www.ysperformance.com/prod63.htm

Propping your below its peak torque can cause damage to your engine.

If YS is specifying a 12x7 and stating that 10,500-11,000 ground RPM is the figure to shoot for.
Going one full size up, can get the RPM below this engine's peak torque.

You can identify the approximate RPM of torque peak by trying increasingly higher load props on an engine, until a large loss of RPM results. This example uses increasing pitch, but you can also do it using increasing diameters (+0.5").

Example: a four-stroke 60 shows the following RPM readings on XXX brand props:

12x4 - 11,500
12x5 - 11,000
12x6 - 10,600
12x7 - 10,100
12x8 - 9,100
12x9 - 8,500

The engine's torque peak is between 9,200 and 10,100; closer to the higher value.
Between 12x4 and 12x7, the engine lost 400-500 RPM, with every prop load increase.
This is because as load increased and the RPM decreased, the engine produced more torque, to produce a smaller loss of RPM.

When changing to the 12x8, the loss was significantly more marked, at 1,000 RPM. This is because the increase in load was joined by a REDUCTION in torque.

I would not use a 12x8, or heavier prop on this engine. It could get the "death rattle" as it is, or it could unload at speed and then become too lean and get the "death rattle"...

Always prop ahead of the big drop.

Sincerely,

deputydog

12x8, 13x6, 14x4! If you are not seeing 11k with these props then something is wrong.... I'm running a 12x8 Master Airscrew Scimitar @ 11,600-11,800 depending on temp. My 53 runs the same type 11x8 at a consistant 11,800.
Back off the hi end and check your valve lash when the engine is cold.

Hobbsy

My Feedback: (102)

If you're watching the exhaust and thinking it is rich, you have to remember that it is pumping the same approximate volume of intake and exhaust as a .91 or 100.