Rotax 503 woes

[Mhetzel]

Good afternoon all

I am an aviation novice and require some assistance and tips on maintaining my 503.

I do not fly as often as as I would like to, but when i go out to the airfield, I struggle fiercely to start
the engine. Being a pull start, this is both a test of endurance and self control... Any tips? I have
already emptied the carb bowls and put fresh petrol in, but I am not sure to what level to fill them.

Whilst attempting to start the engine, petrol comes out of the overflow on the one carb, but not the
other. Nothing was changed/replaced on the engine in the recent past. What am I missing?

My trike does not have a fuel guage and I would like to fit one. Can I fit a normal 12v automotive unit?
Can anyone maybe supply me with a 10 point instruction plan to fit this item?

Thanks guys

[Morph]

Fuel coming out of your one carb is as a result of the float level being set incorrectly and not closing the needle and seat.

Simple to fix, the float is not closing the needle and seat off properly

Bend this little tag (red arrow) slightly up (blue arrow). It presses needle 19 against the seat.

Start the plane, warm it up, run at 3/4 throttle for a while and shut off.

Take the bowls off carefully and remove the floats. The bowls should be filled up to about 12mm before the top

Alternatively replace the needles and seat.

Things to check
1. Are your plugs gapped correctly?
2. Are both ignition systems working properly
3. Check that the ignition systems are earthed properly
4. service your carbs

Are you opening the throttle at all? you must not. It must remain closed and only the choke open.

[Mhetzel]

Thanks Morph

I will check the float levels, etc, etc.

I am not using the throttle at all when starting. How do I check the ignition systems?

[KFA]

I would suggest not setting anything if it was fine before. Strip the carb down and use something like carbcleaner to clean the carb out. Check the needle and seat for wear and if necesary then replace the needle and set the float level again. Also check the plug gaps.

PS. Fly more often and you won't have all these troubles.

[Miskiet]

All the Rotax 2 strokes should start easy. Give your carbs a good clean. Adjust them as per the manual.

Your barrels should be about 8mm from the bottom when the throttles are fulle closed. If they are even just a few mm more open you'll battle to start. Next time your at the airfield just take your filters off and check - they should also be even. Make sure they are fully closed and seat against the stopper screws (big, spring loaded one on the side) - throttle cable should have a little slack when they are closed. If you are still battling lower both barrels a little by adjusting the screws out a turn or so and try again (remember this affects your idle speed). Once your engine is warmed up set the idling to a level where it idles reasonably smoothly (but only once youv'e checked your idle jets are open!)

Always start cold engine with full choke - if it doesn't take on the second or third pull, close choke and try 2-3 pulls, then try with full choke again (Procedure to prevent flooding).

[windswept]

Every engine is a little different and has its own nuances, but I found with mine that after I had checked bowl levels I would make sure that the mags were off, Choke on full and turn the prop through a few times by hand. Then put the mags on, and using the pull start it would start first time every time. I assume that this procedure built up a little pressure in the lines which helped with the start.

Once the engine was running I slowly ease in the choke until the engine is running smoothly. If it sounded like it wanted to cut I would just add a little choke again (Very cold days). I have never had a problem with this procedure.

I agree with the other posts - dont' just adjust things if it worked before, and unless you know what you are doing, get someone who knows what they are doing ie. local AP, to show you how to set it.

Carbs can be fickle beasts so don't just go arbitrarily turning screws. You will most probably cause a grey hair for every quarter turn!!!

Good luck

[Mhetzel]

Thanks for all the feedback guys - I will put it to use this weekend. I am also a believer that
if it once worked and nothing changed, it should still work.

I am specifically concerned about what can go wrong as a result of the passing of time only.

Any tips on how to fit a fuel guage?

[windswept]

I fitted a fuel guage recently. Quite easy really, but there are many posts in the forums. If you need a hand pm me your cell no.

[Stephan van Tonder]

When tey stand for a while without running the fuel evaporates and leave oil behind. Thsi sometimes blocks a jet so make sure they are all open.

[windswept]

When tey stand for a while without running the fuel evaporates and leave oil behind. Thsi sometimes blocks a jet so make sure they are all open.

Just make sure you fly often!

[Mhetzel]

Good morning all

Thanks for the brilliant advice; I did all the "check everything again" and "get
the juices flowing" bits and low and behold, she fired up the very first time!!

You guys rock!