Is this catastrophic?

[Vikingimike01]

so that 16:1 is causing all that carbon, okay

 

[Chrisingippy]

The sellwr has agreed to send a replacement engine. I'd still like to find out what has happened.
I'm also thinking about a different carb. The NT seems too limited in fine tuning...

 

[HumanPerson]

The sellwr has agreed to send a replacement engine. I'd still like to find out what has happened.
I'm also thinking about a different carb. The NT seems too limited in fine tuning...

Looks like the Cylinder studs bottomed out and went through into the case, leaving the broken pieces in your crank case.

At least that seems to be what I see.

Ride Safe!

HP

 

[Chrisingippy]

Looks like the Cylinder studs bottomed out and went through into the case, leaving the broken pieces in your crank case.

At least that seems to be what I see.

Ride Safe!

HP

That's what I thought, but all 4 are sound.
Closer inspection shows that there is no thread after all. It's just damage from the bits getting caught. I've only ever seen inside one of these engines once in a YouTube video. I remember the crank bearings.and casting so am thinking the bits must be something to do with the driven gear shaft or clutch casting in the case.
Its hard to believe 40kms of short trips has resulted in this and that ill have to go back to 16:1 oil mix again..

 

[Frogslayer]

Go to 32:1 gas to oil then jet accordingly, then change your needle setting. In that order lol. The reason you still got crossed thatched cylinder is because it's not even broke in from running to slippery an oil mix (American 2 stroke oil i suspect is way better than what ever they mix in China). Put the engine under load while varying rpms while you heat cycle.

 

[Chrisingippy]

Go to 32:1 gas to oil then jet accordingly, then change your needle setting. In that order lol. The reason you still got crossed thatched cylinder is because it's not even broke in from running to slippery an oil mix (American 2 stroke oil i suspect is way better than what ever they mix in China). Put the engine under load while varying rpms while you heat cycle.

Are you saying to run it in on 32:1? I'm not in the US, but agree on oil quality. I'm using fully synthetic oil.
Before I go the jet route... I discovered that the float level was a bit over 22mm from factory. I changed it, but also, my carby is sitting on a tilt (back toward the engine) because of the bike frame. The fuel tap was barely open at all, yet it allowed the engine to be filled with fuel to the exhaust port and out the muffler. As there's a new engine being sent, I was thinking see how the new float level affects things first. I read somewhere that the 65 jet is used fairly commonly.

 

[CrazyDan]

The diameter of the inner circle of those pieces still tells me it was from bolt locations. It could be from any of the 3 side case cover's bolt locations. The inner circle is too small to be anything else. This will make an air leak and make you run lean. That would explain the carbon buildup pattern, the oil cooked in the direction of the wavefront from excess heat.

 

[Frogslayer]

Break in with non synthetic conventional

 

[Chrisingippy]

The diameter of the inner circle of those pieces still tells me it was from bolt locations. It could be from any of the 3 side case cover's bolt locations. The inner circle is too small to be anything else. This will make an air leak and make you run lean. That would explain the carbon buildup pattern, the oil cooked in the direction of the wavefront from excess heat.

That's good to know thanks. I'll measure, I'd say they are around that bolt size... once the new engine arrives, I may pull this apart to investigate further (and prove to the seller that it wasn't wrong oil mix)

 

[darwin]

The sellwr has agreed to send a replacement engine. I'd still like to find out what has happened.
I'm also thinking about a different carb. The NT seems too limited in fine tuning...

Your a lucky man, most sellers once it's started you're on your own.