421 cub snagged ring?

[knelson]

Buddy came to me and asked if i could put his banshee back together, motor was assembled by a site sponsor and had never been cranked, still had tissue with tapeover the sparkplug holes.

So I put the engine in, set up the 34 pjs to the builders jetting recommendation and it started second kick, and idled almost perfect. A couple of adjustments and on the bike tested awesome,idled nicely, hit like a cub should, and friend was scared after riding it as it came up in third and I guess he's never had that happen... anyways he calls me few days later saying it won't stay idling and could I help jet it. He drops it off to me and it has 50psi of compression, so I dig in. What do You guys think caused this mess (obviously ring snagged) port not chamfered, incorrect ring gap, or what? He just spent a ass load of money on this and it only made it through a tank and a half of gas. I feel bad for the guy. Here's the pics.

[m671054]

Call the builder first. Give them the chance to look at the pics and make a decision before going any further on here. It usually turns into a mess if you follow the path your on.

[sheerider11]

Um, does your buddy know how to mix gas? There's zero cross hatch on the walls, and the oil grooves are gone off the piston.

There seems to be zero lubrication

[knelson]

I definitely will and that is why I haven't named names, just discovered this and wanted to see if anyone else has seen this happen as I would think these are cookie cutter by now..hell I've assembled 3 and I beat the crap out of my serval. I understand shit happens to the best, Guess it was a freak accident?

[knelson]

Um, does your buddy know how to mix gas? There's zero cross hatch on the walls, and the oil grooves are gone off the piston.

There seems to be zero lubrication

I gave him a mix cup and first tank was mixed 32:1 with yamalube, I noticed the wear seemed excessive 

Edited April 21, 2016 by knelson

[sheerider11]

I gave him a mix cup and first tank was mixed 32:1 with yamalube, I noticed the wear seemed excessive

Yeah it looks like it has a ton of hours on it.

Nikasil is really hard shit. To wear it the way it is, that took a lot.

 

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[n2otoofast4u]

I gave him a mix cup and first tank was mixed 32:1 with yamalube, I noticed the wear seemed excessive

What about the second tank? That fugger looks roasted to me.

[knelson]

Not sure. I will ask him tomorrow, and I guess I should take a fuel sample in clear container and check it out

[knelson]

He is prepared to buy new cylinder kit tomorrow from another site sponsor, but I told him to hold off a day or so and I would see what I could do, I wrench for a living so I understand shit happens.

[sheerider11]

Well sell me the old one then

[knelson]

 I probably should just tell him It was lack of lubrication and there is no warranties (It IS posted on builders website) and be done with it. If I convince him it's scrap, he'd probably sell it to recoup some money. I just don't wan't this to happen again, although I've never used this builder, I don't doubt his skills and after talking with him on the phone about jetting it was clear he is a Banshee addict like the rest of us. I guess I should see if builder will give break on new kit, otherwise I'm telling Him to go with FAST (he said he was going to get on ebay and order a cub kit tonight)

[sheerider11]

I for one think there was another issue. And I'm really leaning toward owner related issues.

[sheerider11]

Have pics of the domes and tops of pistons

[knelson]

 

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[knelson]

 

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