YS 91 srx piston and ring opinion

[Lighty]

So theres no reason to inspect the reg? I had it apart and washed it out with fuel only. The line from the tank to fuel filter has no bubbles.

[Rob43]

You just said you checked it already. It's my opinion these bubbles are coming from the tank. I use a Lynx MOAS clunk with my Tareq. Maybe you should try something similar. Another option are the metallic sintered brass variety. An example: LINK

[Matt Nasca]

I've seen a split fuel line in the tank cause the engine to die at half tank or when the fuel gets below the nipple.

Unless you're running a bladder, you'll always have some bubbles in there. At some point the clunk will suck air. You can run a header tank but you'll still get some bubbles.

Also, when you break the engine in, you have to build enough heat to seat the ring. If you run more than 4 tanks rich you're probably going to miss the window to seat the ring. Really all you need is 1 tank of hovering, a second tank of hovering/moving around, a third tank of light flying around, and on the 4th tank you can begin to find your needle settings and building heat. By tank 5, I'm flying it fairly hard and consistant, trying to build heat. By the last tank in the gallon, I'm flying it like normal.

[Lighty]

Thanks Matt.

I tested the clunk, line and nipple. Its solid no air leaking. I think the MOAS is old and the fuel filter might be dirty. Will test this weekend with new lines etc. If it fails I'll try the bladder system. Also the fuel lines were 2.0mm in ID

[Rob43]

I just had some of the Lynx clunk line splt at my main tank fitting on my X50. I was having inconsistent tuning issues with it...I nearly always have. but, the Lynx clunk line is super tight. In my Trex 700N with the Tareq, it has a Lynx MOAS and Lynx clunk line and it's been fine, but both barbed fittings are metal and a bit slimmer, so not as tight. Still plenty tight to seal very well though. I've meant to try the bladder on the Tareq some time, but it runs so excellent as-is, I don't want to touch it. I'm not as up on these as Matt, but I don't think it would have leaning out behavior due to the condition of your ring. If the ring weren't ideally seated, I can imagine it wouldn't have the same compression. My Tareq never has run hot enough for what most would say is enough to seat the ring. I started the season with a new ring and bearings, and took it easy, but pretty much as Matt described. No issues, just didn't develop enough heat to what I thought I should see. Added headspeed and pitch, and it just took it well.

[Lighty]

About to do a heap of testing tomorrow, fingers crossed. I have notice that there is fuel on the bottom of the exhaust manifold .

If there is fuel leaking there could it be the cause to the motor cutting out half tank?

How do I test this?

[Lighty]

Ahhh, all fixed! No air bubbles, leaning out or cutting out half tank. Just a slight leak between the engine and muffler.

[Lighty]

LOL, cannot figure this motor out. I ordered some enya 5 plugs based on the information on HF well, its chewed the elements on both plugs...
Heat sink temp at 95 deg C and back plate 30 deg C.

Very weird. For my style of flying I get air in the fuel lines when the tank is 3/4 down. Going the bladder system now. Not a fan of the MOAS at all.

[mdu6]

Have you fix the leak between engine & muffler ?

That will cause some problems.

While I don't like the MOAS system because of the tiny fuel line they recommend - I use the YS Fuel Tank Clunk (YS-F2083) which is similar to the FuelMagnet and it's working good - well pass the last 1/2 tank - into the last 1/4 tank before you can sometime get a bit of air/variation in fuel delivery.

[Lighty]

I used a gasket that has aluminium in the middle, approx 1.0-1.5 mm thick. Its from rjx which fits a gasser.
I also switched to VP 30% fuel and the glow plugs have melted.

[Lighty]

LOL. Piston is gone.

Is there anything else I need to get?
Piston
sleeve
Rear bearing
Front bearing
Wrist pin ????
Pin retainer?????
Head shim
Cylinder head??

Will post pics

[Baedarlboo]

Ouch...where's the other part of the piston that broke?

[Lighty]

Not sure?

[Rob43]

I'd get the reg apart to make sure no particles blew back. This caused me a lot of grief on the YS 60sr by the time I found a shard of metal in the diaphragm.

[Lighty]

The whole engine is getting stripped. Repair isn't expensive. But will thoroughly inspect it.