Discussion on pipes for 100cc class motors

[wolfejohne]

Branwell ,

Thanks again for all your work. I know you did not get a chance to test the ES units in the air on the DA but what would be your starting point for header length and prop? I have a set of ES coming and was told to use a 13" length header.

John Wolfe
Aeoworks 100CC Extra 300 on the way.

[branwell]

Hi John,

The ES55G ( is that the pipe you have coming? ) has its reflector plate set 17.75" into the pipe.
The KS has it at 21".
Given this, you will need to run 3.25 inches longer headers then the KS1060 to tune in the same RPM range.

I would start with 14.25 with a .25" gap in the coupler and see how that goes.
If it runs well, shorten it .5". You will get a little more power, but you might find it gets the pogo thing going in Torque Rolls. If not, shorten again by .5. If it pogos, extend the gap in the coupler .25". That should stabilize it.

The benefit of the ES pipes is that a pair of them are .75lb lighter than a pair of KS pipes.
The negative is that the ES pipes will be down 200 to 300 RPM to pipes like the RE2 and KS.

For props, I would go with a Mejzlik 28-10. Its got a really firm pull. Not the best downline breaking, but a lot of pull.
If you find you can sacrifice a little pull and want more downline breaking, and aren't too worried about noise, get an NX 28-10 or a Vess 28A.

On tuning the needles.
Start the motor and blip the throttle of idle. If the motor picks up instantly, stop the motor and lean the low speed needle. Keep doing this tell you find where the acceleration just off idle goes soft. Richen it up just slightly.
With the motor cold, you want the low end lean enough that the motor wont take throttle until it worms up a little.

Once you have done that, get a tack and run the motor flat out for a few seconds. What you are trying to find is peak power, so adjust the high speed needle until you find it. Once found, turn the high speed needle rich a 16th and fly the pants off the plane.

Best,

Branwell