67 N15CS Build

[Chris Johnson]

Here’s a running summary of my rebuild of a previously clapped out 67 N15CS. I’ve had this bike for 8 years now, tried to sell it for a while but couldn’t get what I needed out of it so put the engine on a stand on my bench about a year or two back for inspiration. Since then I have been casually addressing the head; more recently I bored & painted the cylinder to build some enthusiasm. Then early in October, on a whim I made the active decision to overhaul everything with the goal of racing here in the desert next April. I’ve raced my unit T100 in the same race twice (registered a third time but panicked and flaked).

Chris

I brought this heap home in 2017 along with a collection of crates holding a B50:

October 5:

Boring stuff:

Seat work:

 

[Chris Johnson]

I pulled the engine apart, noticing some odd weld repairs under the grime. Once I got in there I found one likely original con rod and a mismatched new replacement rod. Also a whole bunch of weld under the timing side rod, likely hiding a big scar from a rod nut backing off. Even though the cases mated up and everything spun fine, nothing about the timing side case was straight or square with all that weld. I mated up a matchless case half that was close in serial number… again the crank & cam spun nicely, I just had to dress the cylinder base surface.

Moving forward, I’ve fit a JS1 cam with his BSA followers, skimmed the head .020”, will be omitting the base gasket and with plain ol JCC pistons should be hitting an honest compression ratio north of 9:1.

With a pair of NOS rods, I still need to have the crank ground & balanced. At this point all the reciprocating parts are weight matched.

The head has been a challenge. My goal is always to get a proper 3-angle (or 4 if there’s enough room) valve seat. The stock seat profile on these heads threw me off… no matter, I set out to fit oversize Kibblewhite valves, until the cam instructions made it clear there isn’t enough room in the chamber for that. I compromised with slightly larger, slightly recessed valves, with marginally improved seat profile & throat ratio. I’ve been able to find measureable improvements in flow with the same strategy on a T150 & VH500 head that I’ve built. Beehive springs are in the mail as we speak…

Chris

Nasty case:

Crankcase shuffle:

Fitting the BSA followers. JS Motorsports makes a really nice kit here and not much more costly than a good set of standard followers:

 

[Chris Johnson]

Bringing this up to date -
I had the frame & parts coated and they’ve mostly been sitting around waiting on assembly. Yesterday, the hardware arrived unexpectedly from the plater. Luckily I took the day off and spent the afternoon playing puzzle.

Looking forward, I’ll be fitting a pair of flanged alloy rims to the stock hubs. I’m waiting on fork stanchions and have been working on getting the damper parts correct - I found early teledraulic parts in there, assuming a fork swap after a crash. I’ll be making a few sensible upgrades once I have all the standard parts in hand.

The shocks are Works Performance & will get rebuilt & tuned.

Chris

Hardware arrived like this. I was expecting chaos but not real impressed that it wasn’t also bagged up. Looks like everything is there and I’m extremely pleased with the cost and finish for cad plate (local platers in LA quoted 4x the price):

Loosely assembled:

​

 

[ludwig]

..I’ll be making a few sensible upgrades once I have all the standard parts in hand.

​

A 'sensible upgrade' would be slider extensions.
The stanchions are already an inch longer than Commando ones.
You can make them yourself, or buy from CNN.
They can be hidden inside the chrome shrouds.

 

[Chris Johnson]

That’s on the list, among a few other things.

Chris

 

[Schwany]

Aside from the engine valve train updates, the swing arm pivot sure looks like a vast improvement. It could be stock though, but seems futuristic for the time period and Norton pre-Commandos. I've zero experience with the N15 obviously.

 

[gpzkat]

Wow, great stuff, good to see you posting this. Just back from another ride on my 66 (or is it '67 - #119799) and it never fails to bring a smile.

 

[gpzkat]

Aside from the engine valve train updates, the swing arm pivot sure looks like a vast improvement. It could be stock though, but seems futuristic for the time period and Norton pre-Commandos. I've zero experience with the N15 obviously.

I remember working on that pivot with my typical janky allthread and washers method to push it apart and put back together on the bench, worked out OK. I believe I may even have put new bushings and grease in!

 

[gpzkat]

Do you have a centerstand? If so, I'd be interested in seeing pics at some point, if you will. Mine has given me fits, and I'm about to tackle it again to get it right - so far, just a bunch of failures. Mine's orientation, based on witness marks, operation, and angle of the feet, were backward, as if someone had set it up for right-side foot usage with the lever/tang. I spent many hours trying to get it to work, but it always fouled the frame, no matter what I tried. I have the right spring, bolts, you name it. I just haven't cracked this nut yet, last one. In this pic, yellow arrow points to front of the bike as it deployed logically/per witness marks etc. Yet the area I'm pointing to is where the tang was.

I'm willing to hear how wrong I am on this but I have figured out every other thing about this bike from a box of bits, complete rebuild. This has stumped me.

 

[Chris Johnson]

No center stand on mine… can’t help there.

Chris