Norton’s Isolastic twin is one of the greatest British bikes. Peter Hatfield looks at it closely – and rebuilds one for us
The concluding episode of a hands-on guide to a nine-month restoration project, in which an 850 Isolastic twin returns to the road
Spurred on by the success of refurbishing the instruments and their pods, I thought about painting the side panels and the fuel tank – the tinware – and wondered: How hard can it be? I had zero experience of painting anything apart from the usual, uninteresting jobs around the house to score Brownie points. It was obvious that there were three important factors to obtaining a good finish: preparation, preparation, preparation.
The tinware with its various dints and dents was duly prepared with lots of fine surface filler and even more rubbing down. Let’s face it: this work isn’t particularly interesting. There’s plenty of advice out there, which I ignored except for one truly excellent gem: use Klingspoor wet and dry paper. When you think you’ve reached a point where the surface cannot be improved, is totally smooth and resembles a baby’s bottom, you come to the first of the interesting jobs: the reveal coat. I sprayed on this coat of primer, and realised why it was called a reveal coat – it revealed many little flaws. Back to the preparation...
With all the preparation and priming completed, you come to the easy part, which is spraying on the top coats. For the main colour I’d chosen Mercedes Benz Azurite Blue metallic, and I like to think it was because it resembled the original Norton Midnight Blue. The reality was that the paint was an obsolete colour, and I picked up six 400ml aerosols at the Somerset VMCC autojumble for the princely sum of £15 in toto. Or, as Henry Cole is wont to say, for the pricely sum… Would someone kindly put him right? Remembering gloss painting in the house, I’d never use a cheap primer/undercoat – a high quality undercoat always gives a better finish. As aerosol paint is very thin, I shot two or three coats of silver wheel paint on the tinware as an undercoat to the thin blue top coat.
Now for the really joyous part: spraying on the blue top coat. I sprayed on many thin coats, and what I discovered was that aerosol
painting was a delicate balancing act. Too thin, and the paint takes on a satin finish; too thick, and you’ve messed up, with the risk of runs and sags that need sanding. I sanded. Used wet, the Klingspoor wet and dry paper tidies up any such incompetence. Once sprayed, I was really happy with the finish on the tank and side panels, leaving only two jobs for me to do: applying the water-slide transfers and pin-striping. A paint shop would be entrusted with the dangerous 2K clear coating.
There was no way that my ham-fisted abilities could deal with wet paint pin-striping. I copped out. Using a few scraps of masking tape to guide an unsteady hand, 1/8” vinyl tape in silver was carefully applied; easy-peasy. The ‘Norton’ and ‘850 Commando’water-slide transfers were applied to the tank and side panels respectively. These transfers came with a dire warning: do not protect with an acrylic based clear coat. I had read this beforehand, and took the precaution of buying some vinyl transfers at the same time as the blue paint. This turned out to be prescient.
After ringing round half a dozen paint shops to have the tanks and side panels clear coated in 2K, not one would touch the job. Thinking ‘Sod it’, and throwing caution to the wind, I applied a thin coat of acrylic clear to a side panel. No adverse reaction. Same with the other side panel. Emboldened by this success, I shot a coat of acrylic clear over the fuel tank, and watched the transfers shrivel and wrinkle in a trice. Oh, cock. (If you’re not a Brit, insert your own expletive.)
I couldn’t figure out why the two transfers should react differently. The problem wasn’t going to fix itself, so I scraped off the damaged transfers, clearing up the mess with the trusty Klingspoor wet and dry paper. Now you can see why the vinyl transfer purchase was astute, as vinyl is not affected by acrylic. Completing the job with many more coats of clear coat, I was cock-a-hoop with the result, even in the knowledge that I was going to have to be very careful with any fuel spillage, as acrylic isn’t that fuel proof.
Compared to the shiny tinware, the frame looked very tatty. It had obviously been repainted at some point, badly, and there were patches of white, which I mistakenly took to be primer. Scraping away at this, it turned out to be oxidised paint. Scraping a little more revealed the original frame paint – paint in pretty good condition. Armed with nothing more than a craft knife blade, AKA a Stanley blade, I scraped away gently at this crud until I lost the will to live. Then I scraped some more. Then I committed a heinous crime. I sprayed the frame with the engine in place. And with Hammerite. I blame it on the mental scars inflicted by the scraping, but the frame does actually look quite good, and not just from 10 feet away.
With most restorations, there are high points and low points, jobs you dislike (see above) and jobs you like. I like, no love, doing electrics. I never cease to be amazed at the banal questions asked about electrics on internet forums, such as: what does this blue/ red wire do? The answer is to look at the wiring diagram, which is no more difficult to read than the London Underground map.
I always do electrics from scratch. Lucas electrics were never very reliable back in the day, and the passing of forty-odd years isn’t going to improve matters. On top of this, more modern components are available. The first items to go into The Box were the Zener diode and rectifier, which were never going to work in my preferred negative earth setup anyway. The Boyer Bransden electronic ignition was spared the ignominy of The Box, since it still worked just fine, as did the 6V coils. Nearly everything else was given the old heave-ho, and the electrical system was completely rewired. With eight fuses. If that’s piqued your interest, and you haven’t dozed off, there’ll be a separate article next time covering the rewire. Right, Frank?
Just as the electrics were upgraded, so was the front brake. With the standard 5/8” (16mm) master cylinder piston, the front brake action
is akin to Roger Moore’s acting: wooden. Some may raise an eyebrow at my solution of a Street Triple master cylinder, but its 14mm piston gives the right amount of feel without being spongy. When it came to the calliper, I couldn’t bear to dump the original Lockheed unit, as it looks so beautiful. It was given a complete overhaul. A Grimeca may work better, but it looks, as its name suggests, grim. A new front disc to replace the corroded original, and we’re done. Or so I thought. There was some oscillation of the front brake lever, which turned out to be both run-out and dishing of the disc – one of a bad batch. Fortunately, RGM stands by its products, and I received a new disc a little while later.
Just when you think you’re making progress, something comes along to bite you in the bum. I’d noticed an oil leak, but the oil was red – a sure sign of ATF from the primary drive. It seemed to be coming from the join between the inner primary case and the crankcase, which was odd, because it had taken a while to leak. Removing the primary chain revealed the cause. The crankshaft oil seal’s sealing qualities were somewhat compromised by the seal being in two pieces rather than the original maker’s intended one. The engine had wet-sumped, and engine oil had leaked past the totally knackered seal into the primary, causing it to fill up. The ATF rose to the top of this oil mix, and finally leaked past the nonexistent gasket between the inner primary cover and crankcase. A new oil seal went on the list.
There are some parts that you can rescue, and some you just cannot. The rear tail light fairing and wheels were in the former category, the seat in the latter. The tail light fairing had a chunk taken out of it, but it was easy to fabricate a new piece, graft it on, and paint the whole affair. It looked good.
Despite looking as though I’d need new spokes and wheel rims, the old ones polished up surprisingly well, so I kept them. The seat, although initially looking like a candidate for restoration, was scrap. The killer was the badly damaged GRP base. Anyway, having a Mk3 frame, I had my eyes on a new, lockable seat by Andover Norton, and the square patterned cover looks super.
And this is the best part of any restoration: completing it by fitting the new, shiny parts. Let me say at his point that I love polished stainless steel. When it came to replacing the exhaust system, no one could touch Armour’s for quality, looks and price. With new stainless hangers and roses from RGM, the new Armour’s exhaust fitted like a dream, and looked like one. The seamless silencers positively sparkle in the sun. I cannot see why you’d choose chromium plated silencers. Or zinc plated fasteners. They’re practically corroding as you’re putting them on. No, for me it’s Dave Middleton’s stainless steel fasteners every time.
The restoration had taken nine months, and I was really pleased with the result, all the more so when the bike passed its MoT test first time. Armed with MoT certificate, NOVA, US title and other sundry paperwork, I registered the bike with DVLA, and received an age-related number. I could now look forward to riding one of England’s iconic motor cycles during the summer of 2017.
So, what’s it like to ride? It’s a bit heavier than a 650cc Bonneville, but a lot lighter than a 750cc Trident, and handles better than both of those equally nice bikes. But the best part is that the Commando’s 850cc engine has a shed-load of torque, and there’s no need for more gears than the four in the box. The US Norton importer was right on the money with the sales slogan: ‘Whole Lotta Torque about Norton.’ Play on words aside, you don’t want to talk about a Norton – you need to ride one. This is one of life’s bare necessities. Therefore, I have a better slogan: ‘Go Commando.’
Take a set of rusty fork yokes, clean them up and repaint them. Great result, seen to best advantage when refitted to the steering head
New front disc, rebuilt caliper
One frame before painting, and the same frame after painting. It’s not entirely usual to paint a frame with the power train installed, but if it works…
And then it’s on with the transfers, and on with the clear acrylic top coat. And then off with the transfers again, because they reacted with the clear coat…
When repainting a fuel tank, preparation is everything. Even if this involves a terrifying amount of rubbing down At last: into primer On goes the silver paint
Blue at last, Mercedes Benz Azurite Blue to be precise. Time for a trial fit to the frame
Pin-striping. Using tape, not a brush
The tank as it was, complete with the dent Removing the dent!
Peter Hatfield’s full house. Two twins and a triple, 650, 750 and 850. Best of British!
A slightly revised view from the pilot’s seat
There should also be a gasket between the crankcase and the primary chaincase. Here’s one now