Royal Enfield flirts with 4 valves in 1930s

Royal Enfield shocked show-goers with its four-valve motorcycle.

 Royal Enfield's line-up for 1931 made headlines at the Olympia Motor Cycle Exhibition. 

"Many New Models," The Motor Cycle magazine reported, "including a four-valve single." 

This was big news. Everyone recognized that a four-valve motor was the epitome of performance,  prestige and, usually, price. On price, Royal Enfield had pleasant news to announce. 

"A last-minute surprise was the introduction of a four-valve model of 488cc," The Motorcycle wrote. Besides the exciting four-valve motor, it had a chrome tank, and then fashionable dual exhaust ports (which gave it a fat, gleaming silencer on both sides, making it look like a twin). 

"It is remarkable value for 50 pounds with a three-speed gearbox, while for an extra two pounds a four-speed box can be supplied." 

Royal Enfield wasn't afraid to put its hot new machine into the hands of the motoring press. A Motor Cycling magazine correspondent who signed himself STAXTON wrote this, in April, 1931:

"I have never had a machine in the Isle of Man that would tackle the Mountain climb from Ramsey so fast as would the four-valve 488 Enfield that I rode this year. That is the chief memory that the machine left with me.

"It would bring me up to the Gooseneck... and then it would roar all the way up to the telephone box at East Snaefell Gate in a manner that no ordinary 'same as you can buy' production model would have done some little while ago....

"The Royal Enfield JF31, as this model is designated, is definitely a fast man's motor. And 50 pounds is not a lot to have to pay for it."

Royal Enfield was enthusiastic enough about its 1931 four-valve motorcycle to continue developing it in the years to follow. But development would follow a wayward road. Royal Enfield struggled to keep its muscular motorcycle affordable. This would prove difficult as the Depression deepened, and sales of all new motorcycles plummeted.

An improved four-valve for 1932.
(From The Motorcycle)

FOR 1932: The Model JF was replaced by the Model LF, with "Many Detail Improvements," The Motor Cycle reported on Sept. 17, 1931. The press liked that the push-rod tubes were now cast with the cylinder.

The cylinder head was modified to add "much more metal round the central sparking-plug hole, and the ports have been altered so as to obtain a rather better shape," Motor Cycling reported. The unstated reason for this would have been to reduce cracking between ports.

Prices actually went down for 1932, to just over 47 pounds. But available power was worth boasting about. Royal Enfield didn't usually release horsepower charts, but this 1932 chart was an exception.

Four-valve horsepower, rpm soar in 1932 chart.
(From Peter Miller's book "Royal Enfield, The Early History."

For 1933: The four-valve motorcycle was now called the "Bullet" with its 488cc motor frequently referred to as a "500." Motor Cycling got an example of it up to 78 mph in a road test. Good news, but with the economy sinking the motoring press gave most attention to Royal Enfield's less expensive  models, including two-valve Bullets of 350 and 250cc.

Again, the press noted that this year's four valve "has a much strengthened head." That cracking problem still?

Why would Royal Enfield offer an "extra" spark plug hole?
(From Motor Cycling)

And this is very odd: The article noted that the four-valve's centrally located spark plug is a 14mm, but "provision is also made for a 19mm plug to be screwed into the side of the cylinder head in the more orthodox position, which would prove useful if the 14mm plug were to fail and another of that size be unavailable." Who ever heard of such a thing?

The 1934 four-valve motor featured elaborate fins.
(From The Motorcycle)

For 1934: The four-valve motor got a redesigned cylinder head with increased finning and a dramatically finned crank case. It looked great. But was the increased cooling effect of the finning yet another effort to stave off disaster?

For 1935: A real switch. The Motorcycle reported that the 488cc motor would have only three valves for 1935 -- two inlet, one exhaust. Improved lubrication, thanks to fully enclosed valves, was given as the reason.

"Justification for this head-form is provided by the performance, which is almost identical with that of the earlier four-valve engine, and by the increase in silence, reliability and neatness of the new engine," the magazine advised, on Sept. 17, 1934.

It would be called the Model LO.

Three-valve motor eliminated the open valves of the four-valve layout.
(From The Motorcycle)

Price was now close to 60 pounds. But not for long. The price was about to drop radically, at the cost of some performance.

By March, 1935, the three-valve had become the awkwardly named "Model LO2." The Motorcycle and Cycle Trader reported that it came with a "not so highly tuned" three-valve motor and a new price -- just under 40 pounds. Maybe performance wasn't worth paying for?

Or was it? The bargain three-valve was a one-year wonder, dropped for 1936.

The hot four-valve was back for 1936, with a straight-up motor.
(From The Motorcycle)

For 1936: Incredibly, the "highly tuned" four-valve was back for 1936, once again dubbed the "JF" (its original name way back in 1931). The price was back up to just under 60 pounds.

Anyone confused yet?

Previous multi-valve motors had all been "slopers," but the new JF four-valve motor sat straight up.

What about those fully enclosed valves, whose lubrication was so  approved of in the LO2? Never mind. The four valves of the JF were exposed, as they always had been, and thus needed to be lubed with a grease gun.

The 1937 four-valve in its final form; the head would be an option in 1938.
(From Motor Cycling)

Onward: The four-valve motorcycle would continue in 1937.

For 1938 The four-valve head became an option on the standard two valve Bullet 500. The two-valve cost 64 pounds and was good for 75 mph, The Motorcycle reported. The four-valve cost 66 pounds and went 85 mph.

That was the end: Royal Enfield and the rest of the British motorcycle industry would soon turn to building simpler motorcycles, for soldiers.

In his informative article in The Gun magazine of the Royal Enfield Owners Club, Mick Lemon notes that examples of Royal Enfield's four-valve road burners of the 1930s still exist, and are appreciated by collectors.

Clutch cable won't work? Here's a fix

Cotton swab shows path of Royal Enfield clutch cable through back of four-speed gearbox.

 "Eeeewwwwwwww," my wife groaned, as she picked up my helmet from the sidewalk and put it into our car. 

"That is one soggy helmet!" she said. 

No surprise. 

I had just pushed my 1999 Royal Enfield Bullet about a mile, with my helmet on because I had no other place to put it besides on my head. 

I had considered abandoning my helmet and returning for it later, but figured that if she came in the car and got it she could also bring me some water to drink. 

I would need the water. I still had another mile to push to get home. Luckily we live in Florida, where there are no hills to push up. 

Several people stopped to offer help. Did I need gas? Nope, got plenty. Did I need to borrow some tools? Nope. I have a full kit on board and could fix the problem -- if I only knew what it was. 

It all started with a broken clutch cable. (This time the little nub on the end of the cable broke off at the lever. Usually it's the nub on the gearbox end that breaks off.)

Luckily I carry a spare cable and all the tools needed to swap it in. I've done it on the side of the road before. (My spare cable is extra long, so it need not be threaded through the nacelle, but can arch over the handlebars.)

This time, however, the moment I set off with my new cable installed, the clutch lever went right to the handlebar and the motorcycle stalled. Once again I couldn't disengage the clutch!

I knew the problem couldn't be another broken clutch cable, so soon. I'd need time in the my garage to diagnose this problem, and that meant a two-mile push home! Ugh.

Thanks to the four-speed Bullet's neutral finder lever I was able to put the gearbox into neutral.

And so the long, hot push began.

The next morning I began taking a closer look. Indeed, the new clutch cable was intact.

The trouble was that the cable could not operate the clutch because its whole end had been pulled inside the gearbox. To work, the outer cable must stop at the gearbox wall and allow only the inner cable to respond to the handlebar clutch lever.

View from behind of hole that must grip outer cover of clutch cable.

Removing and replacing the cable was no help: the first pull on the handlebar lever once again yanked the cable through the hole into the gearbox. Obviously, the hole had grown just big enough to allow the fat end of the outer cable to pull right in.

I'm stumped on how to make that hole smaller. All I could think of was to put a washer on the outer cable to stop it from being pulled into the hole.

It's a bodge, not a perfect fix. The washer barely grabs the shallow ridge at the cable end, and in doing so it holds the cable slightly proud of how deeply it should be held in the hole.

Washer will keep all but narrow tip of outer cable from entering gearbox hole. Note the shallow "shoulder" of the cable that is supposed to prevent it going into the hole, but doesn't. It will keep the washer in place, I hope.

The effect of this is to shorten the reach of the inner cable. It is just slightly shorter, but enough so that I had to leave off the cable adjuster at the lever end to let it reach the ferrule that holds it at the handlebar lever.

I'll replace the adjuster when the cable has stretched enough.

The photos here explain how I made my "fix."

I filed a flat side onto the washer to better fit near the gearbox hole.

The washer I used has an internal diameter of 3/8 inch (8mm). It must be rather a common size as my spare parts bin is full of them. Since replacing the cable roadside will undoubtedly result in the washer falling off and disappearing I put a package of extra washers into my on-board toolkit for next time.

But there IS a better solution: In "My Cart" at Hitchcocks Motorcycles is clutch cable part No. 142453A, for Bullets made before June, 1999 with the Magura handlebar controls. Allan Hitchcock suggested it in response to a question from me.

In an email, he wrote of this cable:

"There is the top hat outer cable ferrule which locates in the case of the gearbox (the originals had a crude domed ferrule). This looks to have a bigger diameter shoulder to the ones in your photo, which will prevent it pulling through."

That's just exactly what I need. 

Finally, I'd like to thank the charming young sales associate at the business whose parking space I used to initially replace the clutch cable. She graciously offered me a bottled drink, which I had the affrontery to refuse, so confident was I that my repair was complete.

How badly I suffered with thirst in the blocks before my wife came to the rescue with a thermos of water. Serves me right.