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.
I had the timing chest components in and out more times than I care to remember as I conducted selective assembly by trial and error to get the best possible fit. So, I’m a bit disappointed that it’s all gotta come out again...
I’ve measured the cam timing a dozen or more times now, I’ve looked at lobe centre as well as lift @ TDC and the bottom line is I’ve got to retard the cam. 5 degrees will get it as close as it’s gonna get. It’s not the end of the world, but I am surprised to have to do it.
The rocker geometry issue was much improved by use of shorter custom made pushrods (very light too, thanks Ken).
I’ve been rather starved of shed time of late, I will try and get some small progress made this week though...
Strong work Nigel. I'll be interested to hear your impressions of the new engine compared to the old one, which was also full of custom parts.
One thing I wondered about was the Maney case breather is on the timing chest, and there didn't seem to be any holes from the timing chest into the crankcase with the exception of the drain hole down low behind the oil pump boss. How does the air get to the port exactly? or have I made an incorrect assumption?
That’s not a breather you’re looking at on the rear of the timing case, that’s the oil return from the cylinder head. This has to be done on a Stage 3 Maney head cos he breaks into the stock oil return hole when he ports the inlets, so it has to be welded up. So, that’s also one potential head gasket oil leak cause removed!
Engine breathing is gonna be taken care of by a cNw reed valve bolted to the back of the crank case ‘Combat style’.
Cam timing sorted. It’s now within 1.5-2 degrees of cock on, being 1.5-2 degrees advanced. I’m very happy with that.
A double check of squish has confirmed the .036” squish gap. And the CR is at 10.95:1. Valve to piston and valve to valve clearances all very good.
So we’re all good. Just need to get to the gym and build the right leg up a bit!
Onto the next stage...
Looking forward to discussion on suspension setup. That art seems to be half the battle before the battle even begins on track. Are you folks limited to swingarm design and double shock setup? Seems very limiting, although that IS the point of vintage racing.
Fantastic stuff on this thread. Much appreciated. My interest is peaked on US vintage class.
A ‘proper’ Norton is needed to add a little british’zest’ to our WERA league.
My rear shocks and fork internals are all by Maxton. Maxton equipped bikes seem to go very well when dialled in and given a good pilot.
I’ll be piloting mine myself, so there’s the main limiting factor straight away!
I went this route due to the forks being a very clear and big issue on track last year.
I don’t think the twin shock design will be a limiting factor with little ole me on board!
We all draw the line where we think things overstep the point in our own place. I’ve fitted upside down Ohlins to old Brits before. But these days I prefer keeping at least a visual link to the original in this regard.
I am done chasing the little kids around the track and will soon be vintage only in the next couple of years. I think we all eventually begin appreciating the old bikes rather than pumping our egos.
A much appreciated thread for all to see and dream. Great work... let me know when you need to sell!
Two steps forwards and one steps backwards every time with this thing...
Inlet pushrod rubbing on the inside of the pushrod tunnel in the head (yep, the stock Norton head, not the aftermarket barrels).
Gonna be a bitch getting in there to relieve some material.
Oh well, stops me twiddling my thumbs tomorrow I guess ...
Ok, basically, it looks like the head was not machined correctly all those years ago (Friday afternoon job)?
The pushrod tunnels were kinda off centre, to tight for the inlet on one side and the exhaust on t’other.
I got a tool down inside and relieved quite a lot of material. Doesn’t look as nice as if I’d got it set up on the mill like you flash lads, but it’ll work!
Brand new rockers courtesy of the good folk at Andover Norton. Jewel like finishing courtesy of the good Mr Pete Lovell.
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