Trex 600 Saga

[vartegrich]

Well after £130 repair bill for the unexpected tail failure of my Trex, it all went back together and off I went to the field ready for its check flight. Tracking was out a little but all else seemed ok.
A quick slow hover up and down the patch to bed things in and just as the passed me, there was a pop and all went quiet. The landing was uneventful and initially the problem was put down to a blown plug. However, all was not well.
A strip down of the engine revealed a lovely big hole in the piston (see attachment).
The question I have to ask, is the hole likely to have been caused by the plug or something else more sinister.

[moonmanflyer]

the engine running lean did that mate, unlucky, sometimes the way it goes

[sacko]

Usually a lean engine.

[Boggy]

judging by the colour of that liner i would say it was well lean!!!

[vartegrich]

I tried my best to keep it away from lean. It has been pumping out a fair bit of smoke, but obviously not enough. I started quite rich and only gently leaned out the engine enough to keep it running reasonably.
The only thing now that nags me, is whether the mixture has been inadvertently knocked whilst I was doing the repair.

[vartegrich]

judging by the colour of that liner i would say it was well lean!!!

The colour is not true.....just a tint from using the mobile phone camera.
There is no noticeable colouring on the actual item.

[Kwickkwack]

A bit late now, but it pays to do a test hover and just check the backplate on the first flight of the day, especially if the weather has changed since you last flew.
Sorry to see that though it just adds to the cost.

[ChrisP]

I agree with the above. I blew my first 50H piston by going too lean about 2 and half years ago. Some awesome power for 3 min then bang - dead! I was unlucky though, knackered my liner, ring and bearings . Never had a problem since then, always keep it slightly rich.
As Kwickkwack says, always check the back plate on first flight due to ambient conditions.

[vartegrich]

I agree with the above. I blew my first 50H piston by going too lean about 2 and half years ago. Some awesome power for 3 min then bang - dead! I was unlucky though, knackered my liner, ring and bearings . Never had a problem since then, always keep it slightly rich.
As Kwickkwack says, always check the back plate on first flight due to ambient conditions.

The backplate check is a bit of a new one to me. My trusty old Rappy with an OS32 has never missed a beat in years.
After the 50 cut out, I checked the backplate which was hot but not so much that you couldn't hold your finger there for a few seconds.
What should be the ideal touch test?

[waveydavey]

You should be able to hold your finger there comfortably. The heat starts to go straight away so you just have to gauge it really. If you pull it away quickly it's too hot and consequently, cold and your far too rich.