Losing power on header tank?

[Gate88]

Here's a strange one.
Flying my Raptor (with OS 50 Hyper) yesterday evening, got right in the zone and decided that although the main tank was almost empty I'd have one last circuit and bring it her in. Halfway round I noticed a big drop off in power, so nursed her back and landed.
As it sat on the floor it was idling slowly and lumpy and then cut out, I checked the temp, all fine, & fired her up again but the engine wouldnt run without the glow plug being lit up.
I dont usually run low fuel, this time tho I had used about 1/3 of the header tank, I fiddled about with the mixture, got it running a little better but still not flyable.
I put some new fuel in and discovered that it will run fine as long as there's fuel in the main tank but once thats gone it starts stuttering again.
I replaced the fuel lines, clunk lines, & the pressure hose to the muffler but it still does it, so long as just a drop in the main tank it's fine but once thats gone it runs like a three legged stallion.

Any Ideas?

[Janek]

Typically the engine will go rich when you get onto the header, its a good warning that you should land.

If you notice a major drop off in power, you're probably running rich even on your main tank.

A glow engine will not start without the glow driver attached, the glow is only maintaned by a running engine, once it stops, you have to reattach it, no matter how short a time has past.

[Gate88]

Typically the engine will go rich when you get onto the header, its a good warning that you should land.

If you notice a major drop off in power, you're probably running rich even on your main tank.

A glow engine will not start without the glow driver attached, the glow is only maintaned by a running engine, once it stops, you have to reattach it, no matter how short a time has past.

I do tend to run a bit on the rich side especially when the weather's hot, so that may be it. I bow to your greater knowledge, but is there a reason why would it start to run rich once into the header?

I realise that the engine wont start without the glow plug driver on but usually once it starts I pull it off after a couple of seconds and it idles perfectly.

[Si Goodchild]

Are you sure that the fuel line in the header tank isn't split? If it is then you'll not get any fuel after you run the header tank below about half way. Also make sure your header tank clunk is moving freely. This problem on my main tank forced my first ever auto!

Si G

[TrexMADuk]

Check that the cylinder head bolts are all tight, I had some come loose had a similar effect - worth checking...

[SRH990]

The outlet pipe on the header tank is usually higher than the main tank. While the main tank still contains fuel, the engine is running on the height of the main tank outlet but as soon as it empties you are then running on the height of the header outlet. As this is higher, more fuel flows into the carb for the same exhaust pressure and the motor goes rich.

[Gate88]

Check that the cylinder head bolts are all tight, I had some come loose had a similar effect - worth checking...

Now that's very interesting! I did notice some black oily looking drops on the front skid bow earlier in the day, did that happen to you?

[Janek]

black oily looking drops

Those are NEVER good, you should always investigate them if you see them, wherever they might appear. The "black" stuff is usually worn away aluminium !.

[sacko]

Check you rear bearing.

[Asid]

Like Si G said

Split clunk line in the header is an easy thing to check.

Hope you get it sorted.

[Gate88]

Like Si G said

Split clunk line in the header is an easy thing to check.

Hope you get it sorted.

That was my first thought but I replaced all the lines.

[Dedcalm]

Wierd, I fly my rappy 50 (with OS50 Hyper) into the header most flights. Usually I land just as the header level drops - you dont get that much time once in the header anyway On my last flight on Wednesday night I hovered about for the whole header without any change in performance until the last drip and rpm increase as it leans out and stops.