Sunday, 20 November 2016

A bad case of the rings

Being a do-it-yourself mechanic is a prerequisite to running an old motorbike and being into DIY requires tools. They are the heart of the business, not that you need so many but invariably it pays to have the right tool for the job.

I have developed an obsessive delight in buying and owning tools. The socket set is the centre of any toolkit, I have a £20 Draper set bought three years ago which has given good service despite the made in Taiwan tag.

I always find myself drawn to tool shops. Only the other day I was rooting around in one and found an old miner’s lamp - I had fleeting visions of being lost in the attic or spending the nights buried under the car, but managed to still the urges and bought some tubing for carb balancing instead.

Secondhand shops are the worst, though. I used to live near one in Lewisham and would spend time rooting around there. I found a Britool torque wrench there for £20. These are expensive and high quality items; I didn’t actually use it for a year or so, but could have been seen in the depths of my depravity, stroking, turning, caressing and feeling the thing and pondering what in God‘s name ever possessed me to blow £20 on something I had no use for.

Haynes manuals are indispensable to the home mechanic, but they follow standard industry practice by charging about twice as much than for the car ones. They also presume a certain amount of common sense on the one hand, and assume you don't possess things like vacuum gauges on the other. They suggest that dealers only charge a nominal sum for balancing carbs, but £17 for a four cylinder bike isn’t my idea of nominal.

So I indulged my passion by buying a set of mercury gauges for £31, figuring to get my money back by doing a few friend’s bikes. It’s a good idea to store them carefully or you will have a cupboard full of mercury.

Having maintained my own bike for a couple of years I had got to know it well and despite my ministrations it was beginning to show its age in typical Honda CB750 manner. A recent MOT failure didn’t help my mood towards the bike, either — I actually saw the mechanic tilt down the headlamp and then write out the fail certificate. Not only was this irritating, it made night riding that much more difficult.

I decided to sell the bike, I wanted £550 for it, an amount equivalent to a year’s expenditure on the machine. It had 18500 miles on the clock and, er, a bad case of the rings. Not having a phone didn’t help my attempts at flogging it, and I ended up having an interesting conversation with a local biker and little else.

Things became serious 200 miles from home, smoke started streaming out of the breather pipe. The rings had gone, the smoke came from part of the combustion escaping past the worn rings and thence out through the breather. Nothing for it but to wield my collection of tools and do it myself.

I prepared myself by reading Haynes and became paranoid about having to change the camchain, as it was endless it meant taking out the crank and looping the camchain over it.

I was working out in the fresh air and didn’t like the colour of the sky. One of the not so amusing habits of Haynes manuals are the way they describe things in one line as if the job could be done in a few seconds with no more than the merest hint of mechanical dexterity.

Even before I’d gotten into the engine, I was sweating and swearing at the airbox, there was hardly any room between the four carbs and the frame. With the aid of a guest who didn’t quite know what he’d let himself in for. I eventually managed to extract the engine and dump it in the living room.

The cylinder head nuts were deeply recessed and there was nothing in my tool kit that could reach them. A trip down to the town secured a 12mm box spanner. This lasted for five bolts then gave up.

Back to town to buy a couple more box spanners. Just as the bolt drew blood and knackered itself the landlord turned up. To placate him, I helped him clear out a shed where I saw a ratchet which gave me an idea. Back down to town to buy a Britool extension and socket for £8. Whilst going around the remaining bolts, I saw that, there were actually cutouts in the head for the use of a normal spanner... use of a handy tyre lever, that I've never used on tyres, helped remove the head and then the cylinder.

At last, I could see the problem, one of the pistons had collapsed not helped by the gaps in the rings all lining up with each other.

The Japs had apparently used some super sticky gasket cement when assembling the engine and short of taking a cold chisel to the head, I could see no easy way to remove it from the mating surfaces of head and cylinder. I eventually stuck the bits in the oven and then used an aluminium scraper I made up and lots of elbow grease.

It took lots of fiddling to get the rings up the bore, more like a 3-D jigsaw puzzle than anything else. I took a gamble on the pistons being in the right place to match the timing marks and pulled it all back together with a few more bloodied fingers and curses.

For the first half hour it refused to start, then as the battery was about to expire it coughed a little. After an hour on the charger, a few kicks and a push on the starter it fired up. A bit rough but after I’d done the ignition timing and reset the valve clearances it was running better than ever, able to hit a ton once again. I’d a running bike and expanded my tool kit so was happy.

Howard Hill

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