OK, so I have to admit that this build has been a tad slow. The problem that I have is that if something isn't quite right, I usually can't live with it, so it either gets pushed to the back of my garage, or I nut it out and finish it. To make things worse, the drag bike came along while I had the ZZR engine in bits, and I really want to get the drag bike/CB750 hybrid up and running by Christmas, when I'll have lots of time to ride it over my 4 or 5 weeks of annual leave in nice warm weather.
The problem I had was the replacement piston. I bought it from a seller in the US who said it was from a 1992 ZX11, which should be the same as my 1992 ZZR1100. But it wasn't. Here's a pic of the replacement piston:
ZZR1100 D Piston by
terry prendergast, on Flickr
Whereas this is another piston from my engine:
ZZR1100 C Piston by
terry prendergast, on Flickr
So while the replacement piston was about the same dia and the same weight (once I installed the rings) it had a longer skirt, front and back. I didn't think this would be a major problem until I rotated the crank and busted 5mm of skirt off when it caught the bottom of the cylinder aperture on the crankcase top, the skirts at that point are less than 1mm thick, so super fragile. Hmmnnnn, I ground the other skirt off and surprisingly both pistons then weighed exactly the same, but without the skirts that piston looked a bit weird, and I just couldn't live with the idea of having one odd piston.
I contacted John in England, the ZZR1100 expert who sold me the crankshaft, and asked him if he had a piston for my bike and explained the problem, and he got back to me right away and said yep, the "odd" piston is from a later "D" model, so he sent me a couple of pics of a C and a D piston side by side.
ZZR1100 piston comparison by
terry prendergast, on Flickr
He's a top bloke, and only charged me 20 English Pounds for the piston and rings, including postage to Oz, so I should have it in the next week or so, and maybe (just maybe) I'll get the engine back together before I go in for surgery on the 31st, because after that I'll probably be out of action until the end of September. Fingers crossed.