How's the cylinder look? Any scuffing? If not, fix it and consider yourself lucky that you caught it.

 

Everything looks reasonably good for a having over a years worth of track abuse on it running 3.5X stock hp. ACL race bearings seem much better than anything else I’ve had in the motor.

I’m still thinking refresh. slight hone, new rings, replace all the wrist pin retainers, etc. I took the wrist pin retainer out of the other side of this piston and it too is bent so it doesn't seat evenly in its groove.

This will also be the 4th time I’ve had the rod bolts assembled if I reuse them, I’m thinking replacement time.

Bob

 

Based on another retainer being bad, I think that's a wise choice. For the cost of a few parts, you'll have peace of mind that it's not gonna grenade on you. At least not for that part.

 

Wow, how does the cylinder wall look, did it wear more on one side from the extra ring pressure from the pin or is that effect minimum ?

You did make out fortunate with that. I had a Honda TRX420 I rebuilt and must have had a circlip come out. It was running fine one day and then suddenly burning oil and stinking up the world the next. After pulling the jug I found a nice big score past any point of reboring. Found a used one on eBay and had it back up running.

 

I'm glad you got away without any significant damage. Your refresh plan sounds good to me. At your power level, reliability is much more important than finding another place to squeeze a few more ponies. Did you pull the head yet? How did that exhaust valve look?

 

Yikes, yeah. That's one thing I won't reuse - too catastrophic of a failure, too cheap to not replace.

 

Carillo A-beam Rod bolts $189 for 8 of them. Not exactly cheap. If It takes a reasonable torque to get the streatch Im told they shuld be good.

Bob

 

The #1 cylinder looks like it had more crusty residue on the face of the exhaust valve like it was burning some oil. Wrist pin up against the oil control ring maybe hindering ring performance? Cylinder wall, pistons, bearings, etc all look fine.

Bob

 

The retaner that broke out was #1 This is piston #2.

Thing was working hard to get out. I am suspecting this piston is toast.

Interesting the Wrist pins and retainers that originally came in the box with the pistons were in packages stamped made in China. The retainer clips were silver in color.

The replacements I got from FM have the same part numbers but are stamped made in Japan on the package. The clips are black and looking heat treated not like silver paper clip material.

Bob

 

If you have stretch numbers from the assembly process, you can measure the length before and after untorquing. If they've deformed plastically, even by .0005, I would replace them.

If you don't have those numbers from assembly, I wouldn't risk it. Rod bolt failure is pretty catastrophic.