Honda CB400/4: Ultimate Hacking with a sting

Motorcycling is one of the strangest games going. I started out young with a Tiger Cub field bike. Rode illegally on the road a few times. By seventeen I had a serious bike in the form of a CB400 four. One of the early F1's - identified by the pillion pegs on the swinging arm. Red, with the original sexy four into one exhaust. 18000 miles, one owner, just ready for some serious riding, I thought. Luckily it came with several boxes of parts. Including the all important pistons and rings. A chronic weak spot, going down every 20,000 miles or so. Mine went, predictably, at 19,400 miles. Much to my disgust.

It was this demise, though fixed cheaply with just a new gasket set, that started a period of decline. I just rode the bike, with the occasional oil change thrown in when the gearbox went really dire. It was always a bit hit and miss but I'd grown up on similar hacks, wasn't that annoyed. The bike was 15 years old then but its finish was still good because bits had been replaced along the way and the owner was devoted to the machine. It took eighteen months of neglect before the rust began to seep out from under the chassis paint.

The petrol tank was the first to go, eventually dribbling out fuel. I actually sent a couple of cops into a frenzy when I parked up in Bristol's town centre. They cited it as a potential fire hazard and were all for having it towed away. Until their tirade was interrupted by squawking radios. They buggered off and so did I. One of my crazier friends, who had decided he was a mechanic after an afternoon's training with a hammer, pointed a welding torch at the bottom of the empty tank...

He reckoned he'd always wanted a bald head. He didn't have much choice in the matter after the petrol vapour caught when he made a big hole in the bottom of the tank. As I said, he was crazy, didn't give up until the bottom of the tank was reinforced with steel plate. You could only see it from underneath, so a good bodge.

He also waved the magic wand at the exhaust system, which was falling apart around the collector box. The work of art exhaust ended up looking naff from the one side. I had to put an inline filter on the fuel pipe to stop the rust gunging up the carbs and the altered exhaust put a bit of a flat spot in the rev range between 4500 and 6500rpm.

This actually added some spice to the power delivery. At best, the CB400's 37 horses were mildly amusing. At worst, it'd gasp along at 80mph on the motorway, into a headwind. 105mph was the most I ever managed. Needing a head between the clocks stance and a thorough workout on the gearbox, with a good chance of ending up in a false neutral, the engine screaming to 13000rpm. At times the need to ride at ten-tenths everywhere was kind of fun, other times it was rather irritating.

One good point was that ridden mildly, as in below 6000rpm, the mill would turn in 65mpg, sometimes as much as 70mpg! Considering that I never touched the four carbs or eight valves in the first eighteen months that was pretty amazing. Flat out, it could go down to 35mpg under adverse conditions. The average worked out at 55-60mpg. Along with cheap used consumables that lasted well, the general running costs were as good, if not better, than most 250's!

Having failed to break the bike in 18 months of neglect, with 38000 miles on the clock I decided it was worthy of serious effort. At that point I'd forgotten the way the pistons went down every 20,000 miles - it had so impressed me that I was blind to its potential faults. Anyway, one complete respray, polish, engine service and replacement petrol tank later I was back on the road on what was generally viewed as one of the classic bikes of the seventies. By then it was 1993 and there weren't that many CB400's left on the road. Either worn out or collecting dust in ever hopeful collectors' garages.

With 41000 miles on the clock, the engine started smoking heavily, with some disturbing piston slap. It still ran okay but I had the feeling that if I didn't do something quick it'd break up on me. A great hunt followed for some pistons and cylinder, only attained after I'd run after some other guy on a 400. He had half a garage full of stuff and three examples of the model! He sold me pistons, cylinder and new exhaust system for £200. Not quite hack country, perhaps, but my mate on a CBR9 spends a similar amount every 3000 miles on consumable replacements!

I even went so far as to buy new gearbox selectors from the local Honda dealer who was trying to shift his seventies spares. I had finally become tired of going from first into about half a dozen neutrals until second or third was finally, desperately, attained. The renovated machine was lovingly pushed into the daylight on a sublimely clear April day...refused to start! Cry? Nope, I swapped the HT leads over, but only after half an hour's frustrated tinkering. You feel a right pillock after doing something silly like that.

This time the Honda whirled into life and wobbled down the road. It had always been a particularly fine handler, even on naff tyres, so I was a bit disconcerted to find it veering all over the road just like my field bike Tiger Cub. A quick look over revealed a loose swinging arm - it would move from side to side. It suddenly dawned on me what the two large washers I'd found on the garage floor were for. Hmmm!

With that fixed it was all back to business, the engine whirring away better than ever before and the bike winning admiring glances from just about everyone. It's a cute, compact thing that dances through traffic just as well as it does through the country lanes. Amazing, really, when you think the chassis was basically off the dreadful CB360G5. I've even had the odd dice with bigger fours, doing them on the corners only to be blown away on the straights. So inspiring was the CB400 in its day that there was a 460cc kit that liberated the true power potential of the engine. Given the way the stocker eats pistons, though, you'd have to be very optimistic to take it seriously. Still, could be fun as a Sunday toy.

For a year I kept the bike in fine fettle but that didn't stop the rings breaking up at 57000 miles. Caused by the small-ends wearing and allowing the pistons to wobble around. Effectively, the crankshaft was ruined. £450 bought a rebuilt engine, which actually vibrated rather than whirled smoothly; newish CB400's are turbine smooth! Nevertheless, it was run in neglect mode for the next three years, doing over 70,000 miles with only three sets of replacement rings, a bit of gearbox work and one rebuilt cylinder head. It would've got the mileometer around the clock had not the speedo exploded at 89000 miles!

The bike is still in my garage but sagging on wrecked suspension and putting out enough exhaust emissions to give an environmentalist a permanent grudge. I've got an MZ 301 for the hacking chores so may well do another renovation job on the 400, as they can fetch as much as 1500 notes. Despite its piston problems it has to be the ultimate hack. Alas, these days, it's hard to find nice ones at reasonable prices.

Mark Wright