Rob, many thanks for that. Looking online and researching the various options I'd like to try and do it myself with a Flex-Hone Silicon Carbide tool (I'm all for learning a new skill if I believe it's within my limited capabilities). The tool is self-centering so even I might not be able to f**k it ...

Well! I'd consider that very sound advice. As you say, I won't know until the mill's running so I think to eliminate the risk new rings are the way to go. I think I was just using you as a sounding board as really I had more or less made up my mind to replace them. I have watched a few LubeToob vide...

I'm guessing you're alluding to a possible ring snapping. Does the metal degrade that much after 45 years? Up until 3 months ago the rings were still on the pistons and in the bores as I rebuilt the engine in 1980 but didn't carry on with the rest of the bike. If there is a substantial risk then I'l...

Need a bit of advice from you guys in the know. 1) Is it necessary to always hone the barrels after a rebuild? The engine is a Z1-B and just over 45 years old but had only done just over 22,000 miles when I stripped it down in 1977. I have reused the original pistons and rings which are all still in...

Cheers young man.

Can anyone confirm whether Z1-B valve springs are handed (or up & down-ed if that makes more sense)? I've still got them in the orientation they came out of the head, by means of tie wraps, but the coil spacings look identical on each end.

Thanks for the warning Al, but I'll just be using heat from a Dremel torch to soften (hopefully) the crud then a drop of Molyslip and a TC tap. If that doesn't work then the crank will have to come out for machine tapping.

Cheers guys. Have ordered some Molyslip from Zoro. Have also earlier ordered some TC taps. Appreciate what you say Zed1015, but after nearly getting a HSS tap jammed in the crank I think I'll go for the harder option. I really don't want to have to go down the route of deinstalling the crank to get ...

Further to my rotor bolt problem outlined in another thread, does anyone have a recommendation for a good lubricant for hand tapping an M8 x 1.25 thread in the rotor end of a Z1-B crank? It would seem that Jokisch paste and Castrol Moly-D fluid are practically unobtainable in the UK.

Al - the CMS site also states that the bolt has been superceded by 115BA0840 which is also what Cradley Heath listed and sent me. The CMS bolt you show is a 115 head ('Upset' head). John Brookes notes in the 6th edition of his parts book that "There are 3 types of 'Upset' head screws supplied b...

As I said in my first post, the bolt is a Kawasaki original part 115BA0840 (replaces 114G0840) and was obtained from Cradley Heath Kawasaki. The bolt has only been finger-tightened into the crank and the blackening at the end is just 45 years of crud mixed with WD40 which I used as a tap lubricant s...

You're drinking and driving?

Having lost the original rotor bolt I ordered a replacement from Cradley Kawasaki. The original was 114G0840 which has been replaced by 115BA0840. I had already checked the thread in the crankshaft with another M8 x 1.25 pitch bolt and found it to be very tight. I thought this was probably due to cr...

Z-Power are still advertising B8ES's.

http://www.z-power.co.uk/spark-plug-set-4-b8es

Didn't think of that! May just bite the bullet and reinstall the head and work from scratch. At least I'll still know which shims are in which buckets from the start. Thanks for your help and thanks to all the guys who replied. Much appreciated.