Discussion in 'Norton Motorcycle Rebuilds' started by Fast Eddie, Feb 11, 2019.
One word Nigel,
Nigel, I really like your aluminium barrels. They must be much lighter than cast iron. With race motors, one of the limiting factors is heat build-up. My near-standard 850 motor loves methanol. If I fitted aluminium barrels, I would probably change to using petrol to get the motor warm enough to race without doing damage from piston slap.
Indeed Al, they are things of beauty... from a functional, utilitarian perspective at least!
I forget exactly but I think they are around 10lbs lighter than stock, that’s a healthy chunk!
Some more progress...
I got the head back from being tumble cleaned, I really like this process, although it ain’t cheap, as it makes the alloy look nice and clean without being polished, and more importantly, it closes up the pores and makes it really easy to keep clean in use.
After quite a bit of double and triple checking (after making some wrong measurements and calculations last night!) and a lot off assembly, disassembly and re-assembly using different head gaskets etc, I’ve finally arrived at what I think is a good position.
I had .040” ‘dishes’ machined into the piston crowns by JS, this was a bit of a guesstimate, I was wanting to be over 10.5:1 but less than 11:1 CR.
I’ve ended up with a .030” head gasket and a .020” base gasket (both copper) and with these I get a .036” squish and 10.9:1 CR, which is pretty much on the top of my target range... it is fortunate that I have the longer T160 style kickstart lever !
I could lower the CR a tad by going thicker on the head gasket, but I’m really happy with the .036” squish and I don’t want to open this up, so will try it like this.
The valve geometry is (strangely) an issue though and I’m currently trying to decide whether to shorten the valve stems and fit lash caps (I’m not really a fan of these as I just see it as something else to go wrong), or shorten the pushrods (they’re Maney steel rods and I’m not sure they’ll be easy to disassemble).
The head came off more times than a whore’s drawers today:
I got these nifty dummy rocker spindles made up, they’re longer and have a knurled end and are machined to be an easy sliding fit in the head, they made life SO much easier:
Could lose small children or animals down here...
I like the knurled dummy spindles. I'll have to make up a set. They would have saved me a lot of time and trouble over the years.
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