Jets Change?

[Hawkeye]

Do I need to change the jets on my Raptor 503, the plane used to be at sea level now in JHB?

[AndyG]

Yes you will. Speak to microlight engines for the correct Jet at your altitude

[Morph]

yes definately

503
Jet Needle 11K2 - Circlip position #2 from top
Needle Jet 2,70
Main jet 158 at Sea Level
Main Jet 150 at Highveld
Idle Jet 45
Air screw .5 turns from closed (i.e. all the way in)

[Bayliner]

Can I assume that the jets would also need to be changed when coming down from the reef to the coast? My trike is in Gauteng and will be in Cape Town in a few months.

[Morph]

Yes the opposite will apply

Remember the air density reduces as you gain altitude. If the sea-level jets are left in, then the air component of the air to fuel mixture reduces with altitude and the mixture becomes richer. Hence you need to reduce the jet size, whch reduces the fuel quantity and thus brings the balance back. However a richer mixture is not as bad for the motor as a leaner one.

When you are at the highveld and come down to the coast the smaller jet will result in a leaner mixture at the coast, (does more damage)

[Bayliner]

Thanks Morph. Will definately remember this.
Might be looking for hanger space at Morningstar one of these days.

[Morph]

[Chris Liebenberg]

Bringing a 503 Raptor from the coast to the reef might need more than jets to be changed. That 503 is going to suffer with the weight of the Raptor at this altitude, unless always flying alone with no pax.

[Bayliner]

Dont think I will have the problem bringing mine from reef to coast other than the jetting changes. In any event it is a 582.

[gavinwolff]

How would this apply on a 912s when flying from Johannesburg to the coast.
Last time, found that the engine was VERY rough at anything below 2500rpm.

If they do need to be changed,

1. What do they need to be changed to?
2. Do you change on arrival or before you leave?
3. Procedure for changing?

Thanks

[Morph]

The 912 uses a Bing 64 carb as opposed to a Bing 54 in the two strokes

The Bing 64 is a Constant Depression Carb with altitude compensation so rejetting is not required

[Mogas]

Rough running below 2500 RPM suggests the idle jet may be too lean for the coast if it is ok at the highveldt.
The auto altitude compensating system is only in operation for the main jet.

[Hawkeye]

Sorry been out of ciculation, but thanks to all for the reply, specific thanks to Morph for the details provided.
This is a 350kg configuration so not as heavy as the 450kg, with 17sqaure wing, but only time will tell if the 503 will do the job up in JHB.

The only good thing is I am aroung 68kg's. Think I will still have probs Chris?

ZU-CFO

[Bayliner]

Hi Morph

Would you be able to help me with the jets change when my trike gets to CT. I will also need someone to fly it from Microland to Morningstar when the time arises. Sorry but I only know how to build high rise buildings and bridges.

[Morph]

No problem,

Main jet 158 at Sea Level
Main Jet 150 at Highveld

for a 503 that is