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Russ
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Today we headed off to a roadhouse middle of Cape York Qld ( Musgrave ) stinking hot day, CHT was fine, oil temp was higher than normal, just under 100, never higher. Fuel was 95 Ron , Caltex.

 

Air time was close to 4 hrs enroute...

 

Landed, turned both mags off, but she kept chugg a lugging.....just as she was about to stop, she ran backwards for a sec or 2.

 

Pull through was fine when we disembarked.

 

Ok you savy guys........what's going on here

 

 

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Today we headed off to a roadhouse middle of Cape York Qld ( Musgrave ) stinking hot day, CHT was fine, oil temp was higher than normal, just under 100, never higher. Fuel was 95 Ron , Caltex.Air time was close to 4 hrs enroute...

Landed, turned both mags off, but she kept chugg a lugging.....just as she was about to stop, she ran backwards for a sec or 2.

 

Pull through was fine when we disembarked.

 

Ok you savy guys........what's going on here

My 2.2 did that a few times when running on Mogas. Since I've stuck to AvGas it hasn't happened again.

 

 

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Sounds like hot carbon particles, probably on the exhaust valve, to me. Have you checked oil consumption for the flight? Other possibility, a mag earthing lead isn't working properly, do you get even mag drops?

 

 

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Interesting, thanks.

 

Bit more.......used to run on avgas only, then I began a shandy mix..50 / 50 all was good.

 

Now on 95 straight with moreys top end lube added and I've got this event. .?? Ambient air temp today was around 36....38 ish on ground. It was hot...

 

 

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It's basically because the engine is hot or has hot parts (spark plug exhaust valve or carbon flakes) or has just run with a bit more power on like an uphill taxi. Idle for a while into wind and make sure the throttle is fully closed or run it out of fuel. It's pretty rough on the engine to run on. The GENET Major was really bad at that . Sometimes it would burst into like well after it had stopped. Could be several minutes later. Nev

 

 

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I've had it happen twice on mine too. The common denominator was a very high percentage of mogas. With 15% + avgas and ensuring the throttle is close properly it doesn't happen. I also use 'flashlube' at 1% and this helps in other ways.

 

BAP

 

 

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I keep wondering why people will go from 100LL Avgas to 95 Mogas?

 

Just because engine manufacturers say you can use a minimum of 95 Ron fuels, doesn't mean this is the best fuel to use.

 

98 Mogas is still a lot cheaper than 100LL (if that's the reason to use Mogas).

 

A lot of the Avgas fuels, specifically in aero engines, often caused run-on, this being the reason most aircraft engines use an idle cutoff, rather than just killing the mags.

 

But more to the point, run-on is more likely to be caused by engines being run hotter than they should, in conjunction with carbi's set up a bit lean at idle?

 

 

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Interesting, got a mail.....sender had same probs with Caltex 95, changed to BP prob gone, although he also changed his shutdown style....revved to 2000, shut throttle, kill both mags.

 

Think I might go back to shady mix with same top end lube added ( moreys ) pity...as I wanted to get away from avgas and it's possible demons.

 

 

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I keep wondering why people will go from 100LL Avgas to 95 Mogas?Just because engine manufacturers say you can use a minimum of 95 Ron fuels, doesn't mean this is the best fuel to use.

98 Mogas is still a lot cheaper than 100LL (if that's the reason to use Mogas).

 

A lot of the Avgas fuels, specifically in aero engines, often caused run-on, this being the reason most aircraft engines use an idle cutoff, rather than just killing the mags.

 

But more to the point, run-on is more likely to be caused by engines being run hotter than they should, in conjunction with carbi's set up a bit lean at idle?

Personally pylon I prefer the 95 to the 98 it seems to keep better and doesn't leave a residue like the 98 does but our local servo now only stocks 98:crying:

Maybe the slight rev before shutdown might help? After giving it time to cool off obviously.

 

 

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Personally pylon I prefer the 95 to the 98 it seems to keep better and doesn't leave a residue like the 98 does but our local servo now only stocks 98:crying:Maybe the slight rev before shutdown might help? After giving it time to cool off obviously.

You fly behind a 912 so 95 is just fine and dandy.

 

 

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I often wonder about the ability of 98 to hold it's octane rating, but fortunately, I tend to have a fairly high turnover, so it's rarely more than two weeks old (from the servo anyway).

 

Usually around four days from the servo to use.

 

 

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My Gypsy Major does that in the Auster and I run 98 PULP. I shutdown by turning off the fuel these days, it takes a few minutes but allows a good cool down period. It is also safer ... no fuel ... no fire, if some dumb bugga pulls the prop through.

 

 

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You "brews" won't change it. It will still happen occasionally unless you run the fuel out. You can do it taxying in if you judge it right. Make a new pre start checklist or placard the panel. It's standard to leave the fuel on relying on the suspect floats to stop it running all over the hangar floor. Nev

 

 

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There is also advice NOT to use shandy mixes. The RON rating for avgas and mogas are calculated differently (I wouldn't try to explain that - get an expert) and by mixing two it's possible to end up with RON rating below 95.

 

Ask an expert or in my case, accept what the experts say and just use Avgas

 

 

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David just before the engine quits does it increase RPM then die? As it runs out it goes super lean it may cause a problem in long run.

 

 

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Ozzie we always ran the fuel dry in the Ga planes we flew. It stops gunk in the bowl too. Never noticed any rev increase as happens with 2 stroke motor bikes. With a hand swing type you looked a goof if you had to push it in but being [email protected]$e$ we tried to make it happen just as we swung into the line of aircraft, at the park area. Nev

 

 

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David just before the engine quits does it increase RPM then die? As it runs out it goes super lean it may cause a problem in long run.

No Steve, just a slight blip and she just shuts down clean.

Two strokes will if you have the mixture set right, they speed up momentarily as they lean out. If they don't, they are too lean.

 

 

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Two stokes suffer bad from it. My triple 750 had a heart attack when i ran out of fuel at high speed.

 

I didn't realise how bad a lean out was until i turned off the fuel on the ol victa, last couple seconds is well over red line.

 

 

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