Microlighters

HELP PLEAS I nead help on the rite jets on a 503 ROTEXfor the ALT that we are on it should be the same as in JBURG we are on 4410ft . We baught a trike from the coast and would like to know wat jetting to use. I was told to use 150 for the main jets but they make the motor start very hard.

We fly with 155 on the highveld (5300ft) and when we go to the lowveld we use 158.

Hope this helps!

Jet Needle 11K2 - Circlip position #2 from top
Needle Jet 2,70
Main jet 158 at Sea Level
Main Jet 150 at Highveld

See here for the calculations

http://www.ultralightnews.ca/bing/bingjetchart.html

DONT FIDDLE - JUST FLY[/b]

Main jet 158 at Sea Level AND Highveld but you use a lot of fuel
Main Jet 150 at Highveld ONLY

BOATCH wrote:I was told to use 150 for the main jets but they make the motor start very hard.

Everyone's given you the right settings AND just for the record, the main jet size has diddley nothing to do with the hard starting of the engine

Thanks for all the input on the jetting topick .What i woold like to know is wat is the worst that kan happen if you use 158 on 4410 exept the feul consumption. Is there a possisibility tha the motor could get damaged because i have done 50 hours on 158s and so far it performs well and have no splutter when applying full power after idle.

Boatch

You are running rich, which is better than running lean.

Do you have an EGT gauge? If you do what do your temps tell you on cruise? they should be between 580 to 600 deg C with the mx being 650DegC. A rich mixture tends to cools the EGT's which will result in less oil being burned and a reduction in performance. An extreme example would be to pull the choke "enricher" out while running. This richens the mixture and you will see a drop in performance. Less oild burned results in the plugs burning black and gunging up quicker. Fuel consumption will be higher than it should and I would think the motor would tend to need to be de-carbed sooner.

You could lean the mixture a bit by dropping the jet needle down by moving the circlip up but I would rather just put in the proper jet size for the altitude.

So in short, you are running richer, providing less power and burning more fuel.

MORPH thanks for the inf now i know that i havent damaged the motor whith these jets. I will replace them with the 150 and then i will have peace of mind. I had an engine out on my preavios motor and after stripping the motor there was found that the seal betwean the gearbox and crank had leaked all the oil onto no1 cyl. I always thaut that when there is no oil leak every thing is fine do not trust the appearance outside. Breake those seal that keep the filler plug in place and check the level .