Microlighters

Hi, please advice

Please help, had so much conflicting advice. Yes I am reading the Rotax manuals

I have a 582 silver top rotax.

I fly mostly on the highveld (petit) but will do the odd flight down to the coast or to the lowveld.

I currently have 165 jets fitted and use 95 octane operating on the Highveld. Is this ok? Can I use 93 octane rather?

When I fly down to the coast(understand that 165 jets must be fitted for coastal operation) what octane is correct for use at the coast?

IF 158 jets were fitted for operation on the highveld only, what type of elevation changes is allowed with the 158 jets fitted? What octane with 158 jets?

Do the 158 compared to 165 jets give worthwhile fuel saving on the highveld?

I'm flying a silver top. When I bought it (at Klerksdorp = highveld) it had 165 jets and I was getting nothing less than 15 litres / hour.

After receiving advice I had 158 jets installed, went over to LRP (Lead Replacement Fuel), carbs balanced and airscrew set properly and now I get 9 litres /hour. Performance improved and temperatures are now spot on (used to be too cold).

On a 1:50 two stroke mix, it used to be a bit smokey, even in flight. Now only smoke on start-up and there after clear exhaust gas.

As to your sea level question. Fly down on the 158's. Change to 165's whilst flying there and back to 158's before returning. Also use LRP at coast.

That is what I was told, and it has worked for me.

Hi Kloot, thanks for sharing.

How many hours have you got on your silver top running as described?

I am thinking on the same lines as you, but did not consider using LRP. Does LRP fuel give a slight lubrication benefit, lead?

I am amazed at how well a 2-stroke motor actually works. The fact that the bearings on the crank are working under such extreme conditions and are only lubricated by what oil it gets from the fuel, and it is not much.

So because of this I am very suspicious of the crank on a 2-stroke. I have seen a higher fuel consumption as beneficial thinking that more oil is getting everywhere. I am not sure if I am right or wrong in my thinking.

My question, is the oil with a 158 jet MORE than ADEQUATE and am I just wasting fuel with the 165 jets. Or, is there a lubrication benefit running the 165 jets that will result in a more reliable crank life.

Spend more on fuel but have a crank that will keep on going, or maybe and only maybe have a crank with a reduced life but using less fuel.

Maybe we must start a thread 2-stroke engine out's and see what is the predominant reason. I am a bit paranoid about an engine out.

You can only get 93 octane fuel here by us...

95 unleaded octane is definitely available. I buy it at Engin

The lead in tradional petrol served as a "lubricant" and LRP has an additive fullfilling the same role.
As for lubricating a 2 stroke too much, you end up with a bucket of new headaches like carbon build up, plug fouling, more frequent de-coking and choking your exhaust system, not to mention under performance.
I've run mine for 55 hours now in the leaner configuration. Total time is 300 hours of which the majority was done at sea level by the first owner with the 165 jets.

Maybe we must start a thread 2-stroke engine out's and see what is the predominant reason. I am a bit paranoid about an engine out.

The quickest way to have an engine out is for someone to open, and work on your engine.

I had a 582 Blue Top and flying it with 165 jets at the coast with EGTs spot on. We have only 95 available at the coast and Rotax recommends unleaded, so I won't opt for LRP...

I would say that the jet size must be determined by the EGT temp. If too low, downsize the jet, otherwise you only burn unnecessary fuel. The secret lies in the EGT temp, as it tells the whole storie about combustion effeciency...

If you stick to the Rotax manual re jetting and altitude you should be ok...they know the engines better than us...attaining Rotax max book RPMs are important as well,

As stated let the EGT gauge and plug colour help you....as long as you understand what they are indicating.

Give it plenty of time to warm up before going to full power and after that make power adjustments slowly/gradually if possible after high power settings...gives the piston a chance to stabilize.

Nick.

Thats good advice Mr A...