2 Stroke oil on Air Filters - 503

[Petrodactyl]

This has maybe been discussed before, and I probably missed it.

All 503's that I have encountered so far tend to accumulate 2-stroke oil on their air filters - ie. the filters get wet. The 582's seem to stay dry - apart from the filter oil, obviously.

I have an on-going argument with my AP, who is convinced that there is something wrong with 503's that do this. He says that it is due to 'blow-by' past the rings. In my opinion this is ridiculous, because it is a 2-stroke, and any blow-by ends up in the crank case, not the intake manifold.

My understanding is that there is always a bit of fuel mixture 'stand off' in the intake manifolds at certain engine revs, because the crank case is already pressurising before the piston has closed the intake port. On the 582, this is stopped by the rotary valve.

Is this correct?

Christian

[Morph]

503's are typically premixed, and thus the fuel with oil enters the engine from the carbs. There is an amount of fuel vapour that wets the air filter. The 582 is different because it is generally oil injected and the oil is injected straight into the crank, not via the carbs, therefore no oil on the filter.

[extra300s]

My 503's filter is clean and dry (only red filter oil is visable)... Could it not be a mixture problem on the carbs?

[Morph]

My 503's filter is clean and dry (only red filter oil is visable)... Could it not be a mixture problem on the carbs?

no as long as your plugs are burning lekker or the EGT's are within spec you are perfect. I think that older worn carbs are more prone as well. No sure how old yours are.

[Biggles]

I have a relatively low hour 503 and noticed a small pool of premix in the inlet when I have taken off the airfilters.

For various reasons it is possible to get some blowback from a healthy engine (I assume).

What worries me is that the filters are known to degrade when they come in contact with fuel. So normal engine running is degrading the effectiveness of the filter?

[Morph]

you guys are worried about absolutely nothing, relax and just fly

[Biggles]

you guys are worried about absolutely nothing, relax and just fly

Cannot fly... have to make do with commenting in the technical section.

[Morph]

OK then, drool and comment away.

When are you back in SA

[Petrodactyl]

Thanks Morph. Your technical knowlege and good sense always greatly appreciated

Don't want to open up the ''Wash/don't wash in petrol" debate again, but the fact that the fuel gets onto the filters means that (in older engines anyway) this is unavoidable. From what I have seen, washing away the oil with petrol makes no difference to the filter fibres, but might cause the filter rubber to harden prematurely. And surely you can get the filter fibres all white, light and fluffy after dunking petrol, by then washing in warm, soapy water?

my deux centimes

[Morph]

Ja I think the big issue is more with the rubbers becoming hard, than the fibres or the paper being damaged. BTW this is anecdotal, i.e. hearsay, I have not seen an official test done that proves different. This I do know, washing the filters in petrol makes the paper dark and I do know that the rubbers get hard from experience. I had to throw mine away after 400 hours because the section that fits over the mouth of the carb was inflexible and cracked.

We are talking about different volumes here, the fuel vapour is a slight mist. Washing in petrol is a thorough soaking and once done the paper is permanently darker.

There is no need to first wash in Petrol and then soappy water. Dishwashing liquid and water cleans the filter perfectly.

This is all personal choice.

[Mogas]

Change your AP Petrodactyl
You answered your query yourself in your first post.
At lower rpms your 503 will "spit" the mixture out of the throat of the carb. It will suck it back in again but some oil will be left behind in the filter.
This can become problematic with foam type filters as the oil tends to build up and can lead to an engine out with an overly rich mixture fouling the plugs.
The solution is to use K&Ns and be sure to give it some horns often, two strokes like to rev, not stutter around at half power all the time.
Mogas

[Duck Rogers]

you guys are worried about absolutely nothing, relax and just fly

HEAR HEAR!
.....and Mogas is right, change your AP

[Petrodactyl]

Thanks for the advice, everyone.

My AP is actually very good, but is an AMO who mostly works on Lycs and Contis ie: he thinks in 4-stroke most of the time. I did not mean to flame him, but rather just hear the voices of experience.

The point that I was pushing is that the K&N filters always get fuel on them anyway. There is nothing we can do about it, and I don't believe that the filters are damaged by it - millions of flying hours prove this. I agree with the foam type filters - I would not use them for this reason.