Sunday, 5 February 2017
Hundred Quid Hacks: Honda CJ250
The CJ was an update on the curiously named CB250G5, which between 1974 and '76 had taken Honda's reputation for building reliable twins to an all time low. The CJ was not very different in basic engine and chassis design. It used the same OHC, vertical twin engine that could trace its history back to the early sixties. The CJ lost an electric start and had several minor internal mods to the engine in search of removing the older bike's penchant for writing off the cylinder head when camshaft bearing surfaces wore out due to lubrication problems.
The CJ was devoid of pinstripes and go-faster stickers, it looked quite neat, much better than the rather gaudy GB. Although not the most reliable device in the world, the CJ can keep running for much longer than the older bike, averaging thirty grand before it needs a major rebuild, although neglect of the 1000 mile oil changes will write off the cylinder head in about twelve thousand miles.
Valve clearances and ignition timing need only infrequent attention (5000 miles). Carbs need balancing every 2500 miles. All this is very straightforward, needs no special tools and makes Brit bikes look complicated.
The engine has gear primary drive, a multi-plate clutch that gives no trouble and a clunky gearbox that becomes more vague with age. Part of the improvement in reliability probably occurs because the engine was de-tuned from 27 to 26hp, knocking 5mph off the top speed, but improving economy.
To get the CJ up to its top speed of 85mph the bike has to be screwed through the gears, resulting in some unpleasant vibration and harsh noise from the top end. The bike is happier between 60 and 75mph when there's plenty of torque and the bike runs along just off the throttle stop.
Economy under mild use comes out at 70mpg, when thrashed it can drop to 55mpg and the bike averages 65mpg. That's not bad going by Honda 250 standards.
The 350lbs can be chucked through traffic with no problems. On typically worn suspension it gets a bit tied up in knots on fast country roads and goes into a gentle weave above 75mph on motorways. But it's nothing too vicious and fairly easy to keep in line.
Girling or Koni rear shocks combined with stronger springs and heavier oil in the forks give a dramatic improvement over the stock bike. On worn tyres the bike turns into a vicious, nasty, remote bastard in the wet.
Rear tyres last for 120 miles, front tyres. go for 15000 miles, chains last for ten grand and front disc pads for eight thousand miles. The disc brake actually works reasonably well in the wet although it does need to be stripped down every 15000 miles to avoid a seized caliper. The SLS rear drum works well and has enough feel to avoid locking the rear wheel.
In the long line of Honda 250 twins the CJ falls somewhere in the middle. Not so fast or usable as the later SuperDreams (but just as long lived), it's better than the G5 on reliability, looks and handling and equal to the CB250K3/4 (but much slower than the K1 or K2) on speed and handling but not so durable.
Problems come from cylinder head wear, camchain and tensioner demise, small ends and the gearbox. All these make fairly obvious noises. Bore wear can be checked by examining the engine breather for blue fumes - it's hidden behind the engine under the airbox.
The CJ is quite a pleasant bike to own and ride, although it has no real strong points, nothing that's going to fuel dreams of greatness, it's competent and adequate. Built between '76 and '77, possible engine problems means it's silly to pay more than a hundred quid for one.