Chang Jiang CJ750 Side Valve – Part 2

Fiery Fred bought a new old-style bike in the shape of a Chang Jiang 750. The first thing it did was to break down. Could he solve the problem?

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The next new day arrived and although I was disappointed not to have succeeded in my epic journey I was determined to get to the bottom of this silly problem. I replaced the plugs, checked and reset the valve clearances and oil, and then started the bike and went for a short ride.

There were no apparent symptoms and she ran perfectly!

I was now somewhat baffled (this is not unusual, I must add), and proceeded to tidy up the wiring loom and also make some effort to cover the car-type battery which hangs on the offside of the machine. I also succumbed to the temptation to fit some BMW tank badges (well, it is one really…) and after completing these tasks, and being quite pleased with the new look, I decided to go for a nice ride to celebrate my success.

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Yes, you guessed: only four miles from home she started to pop and bang and all the indications of ignition problems and or fuel starvation raised their ugly heads again. I stopped and tried to restart the engine. Hey presto, she ran evenly again! So we set off and finished the day with a 30-odd mile bimble through the Hertfordshire countryside, not without some trepidation.

The next day resulted in exactly the same problems, which then became worse, followed by a bad fuel leak from the tap, which feeds both carbs. I made it home, drained the tank and removed and dismantled the tap. Inside is a rubber washer around 16mm in diameter with four equally spaced holes in which line up with a semicircular groove in the tap lever in its three positions; off, on and reserve. This washer was chewed up between the holes consequently letting fuel pass even when in the ‘off’ position. Could this be the problem?

I made up a new washer from a piece of neoprene type rubber I had in stock and whilst doing this I stripped and cleaned the float bowls and replaced the fuel lines. There were small pieces of rubber floating around at the base of the float chambers, which presumably had risen under pressure and managed to block the fuel from the carb… Aha! All was now revealed, I hoped, which it was until it all started to leak again and I re-drained the tank and started again.

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Fuel taps always look so innocent. Just sitting there, all quiet and coy...

This time I phoned John Lawes at BEMW who had supplied the bike. John was surprised that he hadn’t fitted one of his modified tap washers when he refitted the tank and agreed to send me one, which he assured me would solve the problem once and for all. My confidence in this statement was somewhat lacking with the experience so far. To be honest at this stage I wished I had never seen a Chang Jiang and bought the Ural or anything else instead with an electric leg!

The next day the washer arrived and after a little fettling it was fitted and all WAS WELL. At last!

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Since then the bike has run fine if a little hot and the only other problems have been fuel vaporisation due to the pipes running very close to the cylinders, which was easily cured — and the gear selector requiring a little adjustment to stop her slipping out of third. The manual covers all these problems and once you get the gist of the ‘English’ there is no real difficulty there. In fact it is ‘rubbery’, like the Chinese waiter’s soup.

The bike has now covered just over 600 miles. On its first trip to a VMCC meeting it caused great interest — particularly about its reverse gear which is great fun and can cause you to fall off in a backwards sort of way. It is wonderful to watch the true disbelief when someone sees a bike going backwards under its own steam!

The CJ was mistaken for a 1938 BMW R71 by some experts and, at a recent Brough Superior rally, I was asked what year it was — great doubt was expressed as to whether BMW were still making that model in 1957! It all adds to the fun. I did suggest that I might park it near an SS100 so it might clone itself but that didn’t seem to work!

Random Ural Stuff on

(No ChiangJiangs, you see…)

The Chang Jiang is an acquired taste and it is very different from old British iron, but it’s not without its charms. The exhaust note is most unusual and sounds more like a strangled Bantam twin than a 750 four-stroke but I am now getting used to her funny little idiosyncrasies. The gearchange, which is on the left, is of the heel and toe variety which I can’t get used to. This will no doubt be changed at a later date as my size elevens don’t like working it!

I can’t wait to remove the slide stops and ring her neck, with the resultant earth shattering top speed of maybe 60-65mph! But this engine has to be properly run in, in the old fashioned way and that is going to take time and patience, neither of which I seem to have in abundance the older I get. I will also be fitting the alloy finned larger capacity sump which apparently aids cooling a little in hot weather.

Perhaps I should have bought a new Triumph instead? But then again perhaps not, as I feel with time this bike will become a favourite ‘bimbler‘. It is certainly just that bit different.

You can't beat black paint.

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