Left cylinder melt down!

[Lerea3]

Recently did the top end on my 07, did compression test and it was around 85. Guy I bought it from must have been in the top end because the ring end gap was huge! ran fine after top end was done but noticed the left pipe was hotter then right side. All of a sudden the bike lost power and started knocking. This is what I found (pic)

I'm new to the banshee world but have rebuilt many 2 strokes. Bought bike with TORS removed, idle screw kit installed, K&N open box intake, twist grip throttle, park brake removed

 

-New rings, wrist pins, bearings and Pistons.

-ring end gap within spec

-cylinder bor with in spec

-crank well within spec

-leak down was good

-cleaned carbs

-sync carbs by eye

Was waiting to break it in to do a compression test but that ship has sailed! Why was the left side running so much hotter? Air screws were adjusted the same.

 

Thanks in advance.

[sheerider11]

Is it still together?

[Lerea3]

I tried to attach a pic but it's to big. I have the head off and it looks like there was big time detonation going on. I'll try to resize the pic

[sheerider11]

Put head back on and leak down again

[Lerea3]

Jumped a head and pulled cylinder. Big end bearing is completely gone!

[trickedcarbine]

Carbs cleaned? How do the jets in the melted side look?

[Lerea3]

Both carbs were cleaned, 280 mains stock pilots and clip in the middle. The con rod on the big end got so hot it's discolored.

[sheerider11]

Jumped a head and pulled cylinder. Big end bearing is completely gone!

Well, I guess we'll never know.

[salmon_slayer06]

Many have been down this road. A good leak down test is a must. Make sure you check again before you put the pipe and carbs on.

[guns4children]

Never did a leak down. My 421 serv has been running 5 years

[r_gillies]

What does a failed bearing have to do with air leak? Pressure test won't prevent mechanical failure.

 

 

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[bigweav81]

That bearing could've have taken a shit from an air leak........creating a lean condition. A leak down test could've revealed the reason why, and where.

 

sent from yo mammy house.