Suspension linkage gets another shot at life

Instead of working, spent a dreamy afternoon assembling parts onto the newly cleaned up chassis. These pics show how even the most unpromising bits and pieces can sort themselves out. Blasting by Pete at Summit, Paint by Simoniz Three Wheel Steel rattle can, bearings by Dave Silver spares. Unfortunately the four genuine Honda chassis bearings in this linkage were an odd size (24.5mm OD) and thus £73, plus another £18 for the seals. The swing arm bearings, exactly the same thing but 26mm OD, were a tenner for two at Anglia Bearings in Peterborough. The other good source of suspension bearings is Wemoto's website, but they didn't have the full set for the Dommie so I didn't bother this time.

Shock rebuilds

Most people would regard a knackered old oe shock as scrap, and it is – but a decent quality new one starts at £300. So rebuilding one for £180 is worth thinking about.

I've had five shocks rebuilt by Falcon Engineering (falconshockabsorbers.co.uk): a TDR250, VFR750, ZZ-R1100, RRV Blade and now this. Robin Packham opens the cylinder, cleans everything up, and puts in a better-than-new PTFE piston ring, new oil and usually a new damper rod and seal too. He also cuts a thread in the cap and screws it back on. A final gas-up to get the pressure back and the job's done.

I've had the best results with non-adjustable shocks. The rebuilds on the Blade and ZZ-R altered the damping range somewhat. As the Dommie's shock is straightforward (once you've hacked off the plastic outer cover which eventually keeps the dirt and moisture in – note the blocked drain hole in the rusty 'before' pic) I got it blasted and sent it off. It came back quickly and with only a few paint chips on my rattle can-sprayed spring and shock body. On this shock there's nowhere to put the gas valve except the top portion of the thread (Honda must have assembled the original in a pressure chamber). So I lined up the best place and marked it with some tape before packing it in the box.

Robin replaced the spring and fitted the preload collars before Loctiting the valve in and gassing up. I can never change the spring now, or reduce preload beyond a certain amount, but that's OK.

The Dommie they couldn't kill

I guess I had better introduce the bike. It's an old hound NX650 Dominator, 1990 vintage, previously owned by three bike journalists, thus proving that I am acutely lazy when it comes to buying bikes. The price, two bottles of wine to Simon Brown of MCN, seemed generous for a runner with an MOT. But actually once I pulled it apart I realised it was a lost cause.

Oh well. Too late for being sensible.

The main trouble is wear and tear, an engine covered in oil, and corrosion. And Simon mentioned that it burned oil. It wouldn't tick over either, which I hope isn't due to a worn carb.

The pics show the bike after about two hours of cleaning.Plenty to do, but it should be salvageable.

And so to bed

Or at least, back to long-lost owner Fee Kelly. In a final flurry I screwed the last few parts together, ran it up, left it for two weeks and then, suddenly, a courier going to Cornwall had a space. So off it went...

(cue Monty Python Spanish Inquisition voice)

... with just one small problem. Fee couldn't start it. As this was the original reason she'd given me the bike 14 months before it was a bit embarrassing. It transpired that the soft 'mud' which formed as part of the tank electrolysis had settled on the fuel tap mesh inside the tank, and restricted or blocked the fuel flow. The first you know is that the carb won't flood for startup. I should have flushed the tank out moire thoroughly.

Intriguingly a Classic Bike reader suggested another tank de-rusting process, using a solution of water and black treacle left in for 10 days. Same effect as electrolysis, apparently.

The fuel starvation is a tiresome inconvenience, and may need doing more than once, but 20 minutes will sort it. Sooner or later Fee will find the time.

Next project: a 1990 Honda Dominator I bought for £31. My target is a nice bike for £600.

A Vincent Series C wiring diagram

I've also been wiring up my friend Mark's Series C Vinnie, which he's been restoring for about four years. Vincent specialist Bob Culver built the engine and did most of the stove enamelling.

It looks like the simplest loom in the world, but the tail light wires go through the mudguard stays, and you really need a highly trained baby earthworm to grab the cable in its teeth and slither down the inside of the tube, before poking it out the other end. Perhaps the original works at Stevenage had such influence over invertebrates.

Being happiest with Japanese notation, I redrew the loom in that style. I think it's going to work, but if the past pace of the restoration is any guide we could be a few months away from firing the old carthorse up. Or longer.

You can get the loom diagram hi res on this link:

http://www.mediafire.com/?sharekey=28d9934ccbdf5306ab1eab3e9fa335ca3844f2d1a0c32910

BSA anti-vibration mounts

Rebuilding old Brit tat is an infinitely elastic occupation. Most of this is down to pattern parts, which almost never fit and provide hours of frustration.

For example the headlamp shell had the wrong cable cutout (and flaky paint), the headlamp brackets were different lengths, the speedo cable was too long, the tail light fouled the number plate, a fork top cap didn't screw into the fork leg and the headlamp bayonet connector didn't actually transmit electricity. The little rascals had crimped on the brass contacts without stripping the wires underneath.

So when the anti vibe mount on the tank came up for consideration I decided to make one myself. The rubber mount came from an autojumble stand ('tank rubbers', £1.50). The sleeve (which was a perfect fit) came from the wheel spindle spacers of a TS50 Suzuki.

Four hours with a bottom-of-the-range Clarke welder, a grinding wheel and files and Bob's your uncle.

BSA A50/65 wiring loom in colour

Call me a sentimental old git, but I couldn't resist redoing the wiring diagram in colour. You can download the hi res version on:
http://www.mediafire.com/?sharekey=28d9934ccbdf5306ab1eab3e9fa335ca3844f2d1a0c32910.
To my utter amazement, six people downloaded the black and white version. How did they even find it?

De-rusting with electrolysis: the details

This is such an interesting subject I am putting as many pics and details up as possible. I got the idea from Mike Brown's excellent 2009 book Building Budget Brits, which is essential reading for anyone fool enough to own a Triumph or BSA unit twin.

Here's the method.

1. Shake nuts, bolts or gravel around in the tank to dislodge any big flakes of rust. Use a cement mixer if you have one. Remove with old vacuum cleaner.
2. Make up solution of tablespoon of washing soda to a gallon of water.
3. Bung fuel filler holes with Blu Tac and fill tank to brim.
4. Hook up a battery charger, negative lead to the tank body, positive lead to an iron anode suspended over the filler hole, in the soda solution but not touching the tank.
5. Some chargers have cutouts that won't let them pass current when used like this. I used an old mobile charger delivering 500mA max.
6. Leave it fizzing until the reaction appears to stop. It was a few days for me (plus a couple of weeks before I had time to work on it again), but heavier current might speed it up a bit. The rust is being converted to an inert blackish substance. I don't know what the chemical reaction is but I guess it's reducing (de-oxidising) the rust.
7. The process deals with even the remotest corners of the tank. But once you turn off the current you must dry it asap. Mike recommends pouring out the solution (which is not particularly toxic – I dumped it on the gravel drive) and flushing with acetone to chase out the water. I used cellulose thinners (similar thing), then sat the tank in front of a fan heater for half an hour. Dry as a bone.

Did it work? See the before and after pic and judge for yourself. I think so. The orange, rusty smudge you can just see is only under the electrode, where very fine particles of brown sludge fall downwards. Otherwise the entire inside is grey or black.

Obviously it's less stress if you do the job before painting the outside, but the solution (which fizzes over sometimes when a big hydrogen bubble forms inside) is non corrosive on paint and chrome. Also, it helps to scoop out the scum and clean up the electrode (see pic) from time to time.

You can now seal the tank but I'm taking my chances as it is.

The joys (and otherwise) of pattern parts

Seeing as BSA shut down in 1973, it's amazing that you can still get virtually every part. Hardly any of it is original though, and the tinware generally comes from India.

You can get chromed tanks from the very useful Kidderminster Motorcycles (01562 66679), as well as headlamp brackets, mudguards and headlight shells. It ain't cheap: the original brackets I picked up at Stafford were £65 discounted, but I chose the wrong ones. The shorter replacements, for the earlier drop-yoke A50s, were £90 from the equally helpful Burton Bike Bits (www.burtonbikebits.net).

The catch is that this stuff only fits approximately. The chroming and polishing and overall quality is good, but one of the brackets was 7mm taller than the other. It needed shortening with Alan Seeley's disc cutter to fit between the top and bottom yoke. This then leaves a gap which rain and muck could get into, so I'll need to find some fat o-rings or use RTV to bung them up. The 'ears' are too wide for the 7in headlamp shell too, so I Araldited on a couple of washers to the inside to take up the clearance.

The biggest pain has been a new fork top nut. The threads are just too fat to screw into the new (or, for that matter, the old) fork tube. Mr Seeley's thread files and rat tail files have made no impression so far. I really need a lathe.

The picture shows Diplomat finishing off the installation of a new timing cover gasket last Sunday afternoon. What a fine fellow he is.

How to de-rust a tank

If I had a brain I would have looked inside the tank first and dealt with the light dusting of rust before applying the expensive paint to the outside. But no matter.

I went for a combination of mechanical and electrochemical treatment:

1. Chuck in some dried alpine grit, bung all holes with Blu Tac and wrap the tank tenderly
2. Tumble for 25 mins or so in a cement mixer (packed tightly with cardboard and polystyrene blocks)
3. Hoover out the gravel
4. Fill the tank with baking soda solution and electrolyse it using an old iron chisel as the anode, dangled in the solution. Electrical oomph provided by old mobile phone charger (c.500mA)
5. Flush, dry, add more gravel (washed this time) and shake it about
6. More hoovering and flushing, et voila.

I could have coated the inside of the tank with a sealer but the inside looked pretty good so I didn't bother.