Microlighters

Morning,

I have a question about the needle settings on the carbs om my 503.

The Engine is running smooth with loads of power and the fuel consumption is about 13 l/p.

I am using 155 jets on the carbs.

My question is.

The needles are set on the top nodge, which means it is at the leanest setting. I far as I know it should be on the second nodge from the top. I have changed it to the second nodge, but then on high RPM, between 5300 to 6600, the enigne is missing and you can feel it on the airframe while flying. So i changed it back to the top nodge.

What can cause the engine to do that when they are set on the second nodge? Will this make a huge difference on the life time of the engine? Can it cause the engine to run to lean and overhead again?

I have already lost a engine and do not want that again.

The spark plugs is burning almost black with a lot of carbon on them.

Thanks

Martin

No reason why your carbs should not be set at std factory setting jet wise....black plugs could be for a number of reason inc dirty air-filter...worn needle...float set to high....these will give a rich mix,

Maybe time o check your carb over and see what jets are in it,

What type of a/c is it fitted to.

Nick.

Martin,

Speak to Hans at Microland or Mervyn at Skyriders... I am sure they will have answer for you...

Regards

Robbie Shaw (Rhodie)
ZU-BUJ

Are the temperatures, water and EGT normal?
What condition are the needles and seats in? Worn excessively?
Are the slides perhaps worn?
When last were the plugs changed, and is the gap correct?
As previously queried, is the air filter clean?
There are many factors that can contribute.

Maybe speak to an AP with sound experience on Rotax engines.
Don't play if you are not sure.

Hi,

I change the plugs every 25 hours and wash the filters every 10 hours.

I did try different slides from other carbs but the result was the same.

I cannot notice any damage or wearing on the needles and I did replace the main 155 jets with new ones. I have also replaced the needles on the needle & seats which was a bit worn. I did replace the items one by one and did n flight every time. Only to find that the engine is running smooth with the needles set in the top nodge.

I will also replace the other jets soon and see what happens.

At the moment the engine is smooth.

CHT is at about 110 degrees celius and the EGT's are both just above 500 at cruise and about 580 at takefoff.

Thanks

CHT is at about 110 degrees celius

CHT shoud be 65-80 deg C.

Interesting article here:
http://www.challengers101.com/ExhaustGasTemp.html

Martinvt wrote:
CHT is at about 110 degrees celius and the EGT's are both just above 500 at cruise and about 580 at takefoff.

Thanks

Is this a 503? Those temps are 582 temps

bobthebuilder wrote:

CHT is at about 110 degrees celius

CHT shoud be 65-80 deg C.

Interesting article here:
http://www.challengers101.com/ExhaustGasTemp.html

Bob this is the water temps

Hi,

If I look those specs, my CHT is not to Hot.

Very interesting artical about the temparatures.

Thanks

Bobthebuilder

It was Morph who posted the Rotax excerpt.
I am still muddled about 503 & 582, and am getting my temps from the wrong source!

Thanks Morph for pulling this straight.

On a 582 you have a water temp probe on the top of the head, that measure the water temperature. 65 to 80 deg C is correct for this. If you want to read the CHT you need to place a probe on the head itself, usually around the sparkplug, or on one of the head bolts close to the spark plug

Hi Martin,

Are you sure your temps are correct?
It is quite strange for your take off egt to be higher than your cruise egt. If they are reversed I would say that your engine is running quite well.
I would not make to much of a fuss about cht. It all depend where the probe is fitted, and if not fitted around the spark plug, your reading with regards to the manual is useless. Just get a reading for the cht and any variances should be looked at.

Just for interest, what is your rpm on take off and cruise?

Regards,
Dirk

Hi Dirk,

At full power on take-off my RPM is between 6500 to 6650 depends on if if have a PAX or not and EGT about 580, and at cruise it is between 5300 and 5500 and EGT about 500 if I am flying alone.

If I am correct the EGT temp should be higher at full power and lower on cruise.

The probe for the CHT is fitted on the rear cylinder on a cylinder head stud right next to the Plug.

Thanks

Martin

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What type of a/c...fixed or flex...

Is the main jet std spec for your operation...does sound like your running rich for some reason,

Where are you getting your jetting info from.

Nick.