Vintage Thing No.36 - the Honda CJ250T

It was during a rather ribald discussion with some of my motor cycling friends that the question arose -- what is the motorcycling equivalent of an Austin Allegro? My Austin Allegro is a particularly nice example but that doesn't stop them taking the piss out of it. I know that it is not one of the world's greatest cars and some people voted these chubby little cars the worst ones of all time but I like to point out that much of the Allegro's vital organs are shared with the Mini, which, at about the same time, was voted the greatest car of all time. It seems odd to me that two cars with the same engine, gearbox and the clutch from the same manufacturer, and with suspension systems that follow the same damperless and space saving concept, could be both the best and the worst between them.

But, as we say in Cornwall, "There it is and there you are." And as some deeply philosophical type might also say, "Less is more."

After a great deal of thought and many proposals that were discounted either straightaway or after robust cross examining, somebody suggested the Honda CJ250T. Nobody had anything positive to say about this bike and a few of us who had personal experience of one were quite happy to condemn it. The more we thought about it, the more it seemed that the Honda CJ250T was the Holy Grail in our rather pointless quest.

Back in the summer, I spotted this rather smart example at Boconnoc Steam Fair. At the time, I smiled upon it because so many of them were scrapped and even if it was not a great bike, seeing one after all this time brought back many happy yoof-ful memories. In the light of subsequent techological advancements (like reliability), they lost value quickly and their impecunious owners subjected them to unwarranted abuses as they learnt about mechanical sympathy.

Or didn't, as the case may be.

Many years ago, there used to be a delightfully subversive motorcycling magazine in Britain called the Used Bike Guide. The concept was delightfully simple. There were no adverts and no professional staff writers. All the articles were allegedly sent in by real-life owners of the bikes featured and I have no reason to doubt this claim. The only full-time members of staff behind what came to be known as the UBG were the editor and the mysterious and strangely alluring Typing Person who typed out the adverts at the back of the magazine having deciphered the oily scrawls of the advertisers. Against the odds, the Typing Person became a figure of romantic intrigue and there were many instances of almost personal messages appearing to her from motorcyclists the length and breadth of the country who appreciated her "services", prompting her to say that she wasn't that sort of girl. It was all quite innocent, and romantic in a hopeless kind of way. But the UBG was most popular are telling it how it was and not pulling any punches when it came to describing a motorcycle and its strength and weaknesses.

According to the UBG (now on the internet and going just as strong as ever), the Honda CJ250T didn't go, didn't stop, didn't handle, had poor electrics and no style. The build quality was apparently rubbish, the brakes quickly seized up or wore out, the frame was the worst example of Japanese "bird shit" welding and the seats always split and somehow contrived to give you a wet arse even when it was dry.

It's probably a bit unfair to single out the CJ250T from all the other Honda 250 twins of the 1970s and I am now willing to propose that this bike is a two wheeled Austin Allegro and consequently a Vintage Thing. The basic engine design came out in 1974 as the CB250G5 and this bike featured a six speed gearbox, electric start and a front disc brake, innovations which should have assured success. It was a 180 degree twin, too, which meant the pistons didn't go up and down together like they did in the 360 degree British twins yer elder bruvvers and dads raved about.

The styling of these bikes reminds me a bit of my first bike, a Honda CB125S (def'n'ly NOT a Vintage Thing) so has a certain nostalgia value - like old scars might have. But although the 56mm x 50.6mm twin would read to over 10,000 rpm, it was too much of a bloater to be considered a genuine sports bike and that's what the 250 market demanded, because that was the biggest capacity 17-year-old learners could then ride. The G5's main problem, apart from its weight, was a camshaft that ran directly in the cylinder head. If oil changes were neglected, both components could easily be wrecked and although some firms in the UK offered needle roller bearing conversions, most people didn't see the point of this and moved on to something else when disaster happened.

Another problem for the CB250G5 was the CB360, which, with its 67mm bore, was an even more rev-happy beast and gave the same set of cycle parts that the 250 version enjoyed the performance they deserved (although the handling was still too wallowy). The CB360 put out 35bhp and could manage 90 mph. The CB250G5 gave 27bhp and topped out at 85 mph. The only saving grace that the CB250 had over its larger sibling was the 250 limit for 17-year-olds both performance was the main consideration -- and it usually was -- some for the mad two-stroke twin or triple would be the first choice over a lardy four-stroke twin.

The CJ250T, known in some quarters as the 250T, superseded the G5 in 1976. Weight was reduced by reverting to 5 speeds and discarding the electric starter. Less really can be more. Power output and performance remained about the same and it looked a lot better. Unfortunately, quality was still a problem and after only a year a new design of engine was introduced with a three valve cylinder head and a power sapping balancer shaft. This was the Honda Dream that subsequently morphed into the Honda Superdream, and reached it's apogee (good word that) in the form of the CB400N, which some reckon was a better bike than the legendary 400/4.

When you consider the illustrious Honda 250 forebears, the twins of the seventies must have felt like a backward step -- just like the Allegro when compared with its predecessor, the BMC 1100/1300 range. The CJ250T and the Allegro are contemporaries and epitomise the not-so-sensational 70s, although I think the G5 version, with its podgier styling, compliments the bloated lines of the Allegro. Just like BMC with the Allegro, Honda had a succession of stabs at their 250 twins, sometimes making them better with cuts to lose weight (Allegros were hastily revised internally to create more room) or cosmetic surgery to improve their image. If the 250 equates to Allegro 1300 Super (like I've got, I suppose the 360 version would match the Allegro 1750 (I've got a very rusty one of these). You can look hard for sporting pretensions on both the cars and bikes but not find any, which gives them a sort of subversive charm when you drive or ride them quickly.

Most of them have all gone now. They were unlovable when they were new and are now largely forgotten about. The UBG reckons the Honda twins of this vintage needed a rebore at 25,000 miles and big ends at 50k when the rest of bike would warrant throwing away - if the soggy handling hadn't made the pilot do that already. At least the equally soggy handling Allegro is famous, even if it is famous for all the wrong reasons.

So let us remember the CJ250T. With the benefit of hindsight, you could understand its place in the development of a range of highly successful motorcycles, successful in sales terms at any rate. These were not the bikes that killed off the British motorcycle industry. That crime was accomplished by their predecessors. By the time the CJ250T came along only Triumph and Norton were left. These Honda twins were a sensible alternative in a youthful market obsessed with performance. They were best sellers in their day but instantly forgetable. The more I think about it, it seems incredible that this Honda at Boconnoc survived at all.

As usual, then, it seems that I am supporting the underdog. I suppose I'll have to have one now.

I think the die was cast when I read the UBG's assessment of the CJ250T. After pointing out all its deficiencies, the magazine is vital, it was "Don't buy a yellow one -- you'll never be able to sell it."

Nothing but hot air - Stirling engines

I found this chap and his demonstration models of Stirling engines in the model tent at the Boconnoc Steam Fair. I'm afraid I forgot to ask him his name but I had a long chat with him about the Stirling engine and the principles involved. I'd heard of Stirling engines many years ago but had discounted from my sphere of interest because they didn't have any automotive application. Stirling engines operate simply on temperature differentials. Low friction materials have given a new lease of life to this very old concept, named after Rev Dr Robert Stirling who patented the idea in 1816.

Boyle's Law states that as the temperature of a gas in a sealed container increases so does its pressure and the Stirling engine exploits this principle by have a heat source and a heat sink, such as air fins. When gas is allowed in contact with the cold and heat alternately, it can move a piston, displacer or diaphragm, which in turn can drive a crankshaft.

Stirling engines operate on a closed cycle, so contain a fixed mass of gas called the "working fluid", most commonly air, hydrogen or helium. No valves are required, unlike other types of piston engines, and instead of the ignition, compression, expansion and exhaust cycle of the internal combustion engine, Stirling engines operate through cooling, compression, heating and expansion. There are no external emissions and the thermal efficiency increases with the temperature difference between the hot and cold sources.

Very low-power engines have been built which will run on a temperature difference of as little as 7 °C, or between room temperature and melting water ice. This guy had his model engines running on little hot plates powered by small bulbs. He also showed me how one can run from the heat of your palm. The heat sink in this case was the atmosphere.

After years in the doldrums, Sterling engines are now being examined by Powerdrive (of Subaru works rally car fame) for domestic CHPs or Combined Heat and Power units. By using domestic temperature differentials, such as waste hot water or cold air outside, Stirling engines could provide power for households and even enable them to generate electricity for sale back to the grid when it's not required by the householder.

NASA have been developing Stirling engines for use in space missions and the Swedish Navy have used them to power their Gotland and Sodermanland class submarines, although I suspect their quite running has more to do with this than environmental reasons.

So could you use a Stirling engine in a car? Probably not.

Stirling engines take a while to get going and, once running, operate best at a constant speed. It's a fairly low speed at that. To overcome this, a fancy transmission would be necessary and this complication outweighs the Sterling engine's virtue of simplicity. Heat exchanger design can also get a little involved and the power to weight ratio is poor. But what an elegant concept!

NASA converted a 1986 Chevy Celebrity to Stirling power and Ford built a prototype that used electricity to overcome the start up time, which NASA got down to 30 seconds. Norwegian company Think Nordic are experimenting with Stirling engines as a hybrid power source to supplement their range of wholly electric vehicles. That seems to be the most likely avenue of automotive development to me.

On the whole, though, Stirling engines must have a bright future. I just can't see them running around on wheels much.

Wouldn't mind on in a shed next to my house, though, especially if I can sell the excess electricity to the grid.

Beautiful Boconnoc

The good weather that we had for the Boconnoc Steam Fair in July is now nothing but a distant memory. Everyone I spoke to said what a great event it was. In previous years, some have said that the atmosphere was a bit "clicky" and that previously the organisers were only interested in the steam engines but this year there was a good overall balance and no complaints about unfriendliness. There was a fine range of exhibits, too, although decent autojumbles seem to be things of the past.

Everybody seemed to be there. If you hadn't caught up with old friends for a while, here they were, polishing their cars or riding on their tractors.

The surroundings in the great park are magnificent with the big trees and rolling landscape down to the house and the lake.

Some of my neighbours from up the line called Boconnoc Bock O'Nock when they moved down here and those of us who should know better have started saying it, too. It should be said like B'con'c with the accent on the second syllable.

There even two examples of Hillman Imp at the show. I'm Cornish Centre Area Organiser for the Imp Club, but I've found that not many club members like to get involved with the club locally. It was nice therefore to see this very nice Husky as well as the Sunbeam Stilleto of local stalwarts John and Sarah Doughty. It belongs to Kevin Richards (I think that was his name) of Saltash and is a car that belonged to a very active lady club member for a while. It's in very good condition despite one or two paint bubbles and is a rare variant of the Imp. I was very pleased to see it again in such sympathetic hands.

The only problem with Boconnoc now seems to be its popularity. It took me half an hour to get into the car park. Leaving the site was more difficult since an ambulance had been called for someone. Cars waiting in the queues suffered fuel vaporisation in the heat as their engines idled. Some had to park up and wait to cool down. People complained at the time but if they knew what weather was around the corner they wouldn't have said a word and just enjoyed the rays.