Piston Sizes

[Dr. Frankenstein]

Hello once again, all.

I have a question about pistons; what are the stock dimensions for a 1964 CA77 pistons? The book I have (for a CL72/77) describes the pistons as 53.65 - 53.70mm wide across the top(Top Diameter), and 54 mm+/-.02mm across the shaft, or skirt, or flange, or whatever you want to call it...(the main body of the piston below the rings...).

The pistons I took out of my 1964 CA77 measure 59.5 mm across the top, and 60 mm across the body...are my cylinders oversize?? What are the complete stats on CA77 pistons/rings?

My cylinders are measuring 59mm across the crown, from outside edge to outside edge, and it looks like 59.2mm across the body(outside to outside)...what should the correct specs be, for a standard piston? And how do I know if they're NOT standard size pistons?

And FYI, if anybody has had a bear of a time with the bolts on the oil pump, 6mmx14 buttonhead Allen bolts are a great fit, once you break the molecular bond the oold bolts seem to have with the aluminum...but what's a good way to get the circlip off to check out the pump's innards?

And, FWIW, I came across a new tool (to me) called a Grabbit at Lowe's; $8 for what is essentially an E-Z Out, but you use it with a reversible drill, and it works! No more fumbling around trying to get the EZ Out to stay put..

-John

[G-Man]

John

The 54mm (approx) dimensions are for a 250 motor. The dimensions you gave are for STD bore 305.

Oversizes go up in increments of 0.25mm. You should find the new / worn clearances in your manual.

Sounds like you're having fun.


G

[Dr. Frankenstein]

What Up, G?? :)


Yeah, the book I'm working from is the Clymer Collection Series Vintage Japanese Street Bikes manual; the book covers CL72/77's, but not the CA77 specifically, although it DOES say to use the 72/77 specs for the CA77. The engines are close enough together that it's a great reference, but whenever I run up against something 'out of spec' (like the piston sizes) I ask questions...right now I'm at the point where I've gotten everything on the engine OFF, so now it's a matter of waiting for the cash to get the gaskets and pistons, rings, etc before I put it all back together again. I'll probably turn my attention to the rims and paint prep, and getting the head blasted.

I was really surprised at how easy the camshaft bearings tapped out of the cylinder head, and how easy they go back in. This my first true engine tear-down, and I guess you're only a virgin once, y'know? And it wasn't running anyway, so I just went for it...the hardest part so far has been getting all the butter-soft philips heads screws out and replacing them with Allen heads...I swear, you just LOOK at them and they strip out!

Good to know about the pistons; I thought it was a standard size; the bike only has 8,000 miles on the clock, so it should be like new...so yeah, I guess I AM having fun!

How's Your project coming along...?

-John