Topic: Well, the bike didn't make it to the mechanic today. PROBLEM FOUND 5/25

[Stev-o]

FYI Dolomite - last time I blew up a 836 motor [rod cap through the case] I ended up buying Wiseco 836 pistons along with an already bored out cylinder from forum member Bill Benton.
Was the best route to go.

[scottly]

Yes, to the plugs. And engine is already bored to 836, so if the cylinders can't just be honed, the question is which is easier/ cost effective: resleeve the 836 or bore over to 890?

Those pistons are standard, stock pistons, not big bore. Notice the STD stamp?

I know what the stamp says, but I have the receipts showing the bore over to 65mm and the 836 piston. There's a reason they came in a white box, and the next set will be Wisecos

At first look, your piston tops looked similar to 392 pistons, but now I think it was an optical delusion.
Brian, the standard 350 twin pistons were 64mm, so forth-over pistons were used for the 65mm 836 kits.

[754]

 If they are 64 mm  it is 811 or 823 and may clean to 836.
 Then they may be marked std. They would have high domes  and be quite high compression, which may play into it, with the wrong gas they would rattle easily.
 So I looked at the pistons again and by how far cutouts are from edge of piston, looks like from a 350.
 And look at the aluminium drops , they look squished, like between head and piston.
 But I am not sure where the drops came from..

So I am guessing you had a tiny hole in piston, when you started. As you rode over there it overheated quickly and the hole got bigger quickly, so whatever's  wrong was producing mucho heat.
 Your plugs are close to correct range ?

[PeWe]

Not Cruzinimage 836 pistons?

[Henning]

That blown piston will have dumped a lot of crap into the bottom half of the engine. You really need to get in there and clean it out. Had that happen to me on a two-stroke.

[Dolomite]

Dropped the cylinders off at the machine shop today, they said it likely won't make it onto the machine until Monday, but they'll call when it does and let me know how the cylinders look

[ekpent]

Not Cruzinimage 836 pistons?

He doesn't want to divulge the brand or seller only that they came in a "white box". I think I know 

[Dolomite]

Not Cruzinimage 836 pistons?

He doesn't want to divulge the brand or seller only that they came in a "white box". I think I know 

Yes, I'm not trying to bad mouth anyone.

[754]

I don't care whose pistons, likely not the problem..  but size and bore condition dictates which way to go..
 Even forged pistols can get holes, just takes longer...finding the cause, that is the major problem.

[scottly]

This motor has had problems since the rebuild:
http://forums.sohc4.net/index.php/topic,181434.0.html

[Dolomite]

The smoke was likely the pistons beginning to melt as oil was able to escape past the rings.

[scottly]

Why was oil leaking past the rings on a freshly assembled engine?

[PeWe]

Not Cruzinimage 836 pistons?

He doesn't want to divulge the brand or seller only that they came in a "white box". I think I know 

I have a set of new 61.5mm Cruzinimage pistons. They are in white boxes as another CI kit I used before.
Best thing here is to open the engine completely, clean and inspect it. If not, it will most likely fail and cost more.

As written in earlier posts, too tight ring gaps might be the starter of this failure.

Fix all quickly, have good rides and forget is they way forward.