Norbsa 850

 

For the development history of the Norbsa see below.

Photo taken on Madeira Drive Brighton Sept. 2012, Ace Cafe Reunion weekend.

A great ride down apart from the last 2-3 miles with scooters swarming all over the road.

 

 

May 2005

At last it's done. After several false starts it's taxed and tested and ready for some riding

 

The Norbsa was first finished in 1997 and to get it to it's present state involved one or two developments

The introduction is a bit long and tortuous, but bear with me.

The earlier incarnations

 

 

 

 

Photo taken 2001

Back in the early 1980s I was at college studying domestic electric installations on day release. Although I never went on to be an electrician much of what I learnt became very useful later.

One of the lessons was workshop practice which was a bit superflous as I was a supervisor in a production workshop during the rest of the week. Towards the end of course we had to choose something to make as a project for the exams, so I decided to make a hexagon shaped oil tank for an A10 lowrider that I was building.

Having cutting, folding, welding and brazing equipment to use and more importantly people to show how they were used, I made made something quite neat.

It was installed in the frame and the rest of the bike loosly assembled around it, but I lost interest and finished it off as a more or less standard Super Rocket and sold it on.

Fast forward to the late 1980s and a friend of mine, Penny, was pressed into feeding my cats when I went away on holiday for a month. She wouldn't let me give her money, wine or accept any of the usual offers but asked for my hexagon oil tank as her boyfriend was building her a Triumph lowrider. It wasn't doing anything but taking up space in my garage, and I thought I'd outgrown 'chops' anyway.

Further forward to the mid 1990s and I'd lost touch with Penny and more or less forgotton about the oil tank, but what did I see winking at me from under a bench at a Kempton Park autojumble but my long lost hexagon oil tank. Penny had never used the oil tank and had given it away and there it was for sale for £20.00. I had to buy it back of course.

It had sat on a shelf in my garage for a few years already so I decided it had to find a proper home. It was designed to fit an A10 frame and another friend, Harley Malc, had one lurking in his garage that had been part of another failed chopper project. It had been de-lugged but was otherwise sound.

That was the frame but what about the engine? I happened to have in the loft an 850 Commando Mk111 engine. So that was it, a NORBSA

 

Photo taken 1997

Using an earlier Commando cradle with the isolastics mount cut off allowed the use of a Commando swinging arm and back wheel, which was built with an extra 10 MM offset as the engine on a Commando is 10MM towards the right as you sit in it. This limited the tyre size to 110 x 18 rather than the 5.00 x 16 I would have preferred. A 750 chaincase was used which fitted with the use of a spacer between itself and the crankcase which just allowed the longer Mk111 crank to fit inside, although I had to remove the strobe timing scale. All the welding and most of the fabrication was done by a good friend Little John.

 

The front end was to be a struggle. I wanted to use a Commando wheel so used Commando yolks with spacers made up to fit taper rollers intended for the A10 frame. This looked alright in the garage but outside on its wheels it was decidedly low at the front and seemed a bit short.

I fitted a Sportster tank, Bates headlamp, homemade seatbase (covered by John the stitch in Thame). I'd long since changed jobs and various bits and brackets, made at work where I no longer had use of the machinery but only threats and bribes to get the work done, finished it off.

I'd had the crank dynamically balanced by Nourish to 75% which was anybodies best guess but it still vibrated a bit. Probably no worse than a 750 Bonnie, but I was used to a super smoooth Commando by this time. Foam rubber grips helped.

I'd fitted a belt drive and geared it to 4:1 thinking that with the lower weight the higher gearing would be about right. But it was a bit tall so I fitted a gearbox sprocket with 1 tooth less. Yes I know you want to know how many teeth, but it was a long time ago.

Straight line stability wasn't too good, but it through itself into corners. The cause of this and the rather stunted look was the Commando yolks. Look carefully the next time you see one and you'll notice that an imaginary centreline drawn through the yolks doesn't run paralell with the forks but bisects it just above the ground, meaning there is decidedly odd geometry with any other frame. The Commando frame has greater rake to compensate. Added to this the Commando forks were about 1 1/2" shorter than the A10s ones, which all contributed to something needing to be done.

I bought a set of ally yolks from Icarus engineering (Andy Molnars dad) intended for a Featherbed and had a spindle made up to suit the headstock bearings. The longer staunchions were intended for one of the AMC/Norton hybrids, the P11 I think, and were the right length. They weren't available chrome plated so I sent them off to a firm advertising in the OBM to have them ground and hard chromed. I'd had a set of 20% lighter springs for the rear Konis specially made, so I had a set of lighter front springs made from a pattern to suit.

These alterations returned the steering to normal but the forks would hardly go up and down. I spent some time bouncing around before I discovered that the springs had been made too long, giving too much pre-load.

 

These were shortened and the front end assembled again. I then discovered that the forks would go down but not return. Oh joy.

A lot of time was spent trying to align perfectly aligned forks, and I eventually found that t0he precision ground staunchions were 6/10ths. of a thou. over size. Not much but enough to prevent them working properly.

Starting was never good, despite the Mikuni carb. and I had 3 boyer Bransden twin output coils fail before I eventually returned to twin coils, which also cured the starting problem. The battery box had been built around a too small battery and 2 of those shook themselves to pieces before I fitted 2 gel batteries intended for a fire alarm which has seemed OK. Subsequently a Westco AGM battery has been OK for about 5 yrs.

The cylinder head had been fitted to my old Commando that I'd just sold and had been gasflowed and polished. I'd kept that for 17 years so I may do another page on that some day.

So what did it go like? Bags of torque low down with impressive acceleration, but around 5000 rpm the vibration is getting harsh. That's around 90 which is quite enough with those high bars. Handling is good in a slightly ponderous way due to a longer wheelbase resulting fron the Commando swinging arm. The floating front disc brake came from RGM with a competition caliper and stops the bike well. A fork brace was needed to prevent the forks twisting.

Oh yes, with the shorty meggas also from RGM it sounds good.

This is all retrospective now as the Norbsa is in bits. I took it apart to have the frame nickle plated. There was lots of expensive remedial work to be done, but the plating itself was cheap at £80.00 and looks good.

November 2004

So there we have it.. The first photo of the rebirth of XXK 111 ( Haven't mentioned the reg.no. before, what do you think?)

The rest of the bike's mainly a reassembly job as there wasn't much wrong when I took it apart . I've had the exhaust port threads done, which is why it was taken off the road and languished in the garage for a few years.I also had the gearbox cover machined to take a proper oil seal on the kickstart shaft.

 

I previously had RGM articulated ball tappets fitted (a hardened steel ball, with a flat where it touched the valve, sat inside a cup on the botton of the tappet adjuster). The idea was to spread the load and prevent wear to the valve tip. The problem with the design was that they are longer than the original tappet adjusters which screws up the operating angle of the rockers.

They stopped wear to the tip of the valve but the guides and surprisingly the valve as well wore prematurely, so I've replaced them all with a standard set. I also had spaced out the rockers with solid spacers with 3 thou. clearance to dispense with the double coiled Thackaray type washers, but these caused a surprising amount of noise so they've gone as well.

I had fitted a compression plate under the barrell in a vain attempt at smoothness so that's gone too.

I'm replacing all the bolts that I didn't last time with St./St. am using a double ended Kawasaki 550 type coil instead of the twin set-up which under such a small tank looked a bit untidy. It gives BIG, FAT ,BLUE sparks so hopefully the lousy starting that plagued me from the first day will be gone.

The tank and mudguards are sprayed once again in a deep metallic green, this time properly, not an aerosol in the back garden. Its' the colour of a Kawasaki ZZR1100 I used to have and appears to use bronze coloured 'metallic bits' and looks beautiful. It took the painters 3 goes to get it right mind you. What is it about painters, polishers and platers?

As you read this I've got the wheels in and will take some more photos if it ever stops raining.

Before I take it off it's box on wheels it has to have a stand. Guess where both of them are? Correct, at the platers, where they've been for 2 months.

 

 

May 2011

Late 2007 the petrol tank split at the front. I tried to repair it without any sucess. This coincided with the start of other work so the Norbsa's been off the road for a few years now.

Summer 2010 I picked up a genuine Harley Sporster tank at an autojumble & had the fixings remade to suit the frame.

Despite fixing the geometry problems with the yolks the steering was never as good as it should be, so I stripped off the front end & all the primary drive & took it to Maistone Motoliner who pushed & pulled until it was straight. 3/4 of a degree too steep at the headstock and surprisingly a fair bit off to one side was the verdict

All back together now & it handles really well, well worth the effort & expense. Not good value by the hour but the end result more than justified the cost.

Everything else is as it was before, with a bit more tidying up. Amazingly it started 2nd kick after 4 yrs in the shed. It's got an early Boyer Bransden Micro Digital ign. which looks very like the old BB Mk. III & uses the std coils. I've lots more modern Pazon ignitions around but this works OK so it's staying put.

 

 

 

P.R.Goff 62 Clare Rd. Prestwood Bucks. HP16 0NU
Telephone: 01494 868218 or mail me here Goffy