Friday, February 9, 2024

I fixed my Royal Enfield Bullet! Maybe

 The old Royal Enfield Bullet, made in India, is a simple, single-cylinder motorcycle. One spark plug! 

Early ones have no electric starter, no fuel injection, no disc brakes and no electronic ignition. The pushrods are easily adjusted through a panel in the side of the motor opened by removing a single nut. 

So, when something does go "wrong" with this simple machine, the problem is very likely to be something very simple. 

But finding that problem can be confounding. 

I was privileged to re-learn this lesson the other day. 

My 1999 Royal Enfield Bullet normally starts after a couple of kicks, or maybe three. But, this time, the first kick was accompanied by a small "pop" and subsequent kicks seemed to do nothing.

Looking down past my legs, I saw that the carburetor was no longer attached to the motor. It was hanging from the air filter box. That "pop" had blown it off.

One can't expect the motorcycle to start without a carburetor.

The rubber hoses connecting the carb to the motor on one side and, on the other side, to the air filter box, are awkward. Of course they have to fit tightly to prevent air leakage, and so it is something of a struggle to get them back on.

A bit of grunting and they were back on. I kicked again. "Pop." And the carb was, once again, hanging from the air filter box.

That's not really surprising, since I had done nothing to fix the "source" of the problem. That's because I had guessed that the awkward hoses had simply slipped off, perhaps loosened by vibration, and left the carb hanging.

But if that wasn't the problem, what was?

I reattached the carb, getting it on really tight this time. I kicked again. No joy, but at least the carb did not pop off the motor.

I tried experimenting with the enrichment lever. On. Off. On. Off. No joy.

I always set the Bullet's idle high before trying to start; my Bullet seems to like that. Perhaps I had gotten it set too high and given the engine too big a gulp of gasoline? I dialed down the idle screw and I kicked again. No joy.

Next I pulled the spark plug to look for clues. It was dirty. I cleaned and reinstalled it. Then I kicked again. No joy.

I removed the cover of the points set, and used a business card to clean the points. Then I kicked again. No joy.

The spark plug, although now clean, had looked pretty ratty and old. I pulled it again and put my (by no means new) spare plug in its place. Then I kicked again. No joy, but the motor sounded hopeful.

What if I had already found and fixed the problem, but the fact that I had turned down the idle was preventing the motor from starting? (Remember, I said my Bullet likes the idle turned up when starting.)

I turned up the idle and the Bullet started! I suited up and rode off, with the motor cheerfully racking up plenty of rpm.

Too many rpm.

I turned down the idle, but the motor continued to run fast. Turned it down some more. Still fast. Turned it down a couple more times. Still too fast. The idle screw seemed to have no effect.

OK. OBVIOUSLY, with all the removing and replacing the carburetor on the motor the throttle cable had gotten snagged where it enters the carburetor and the cable was pulled just enough to keep the engine rolling at a frantic pace. While waiting at an intersection I reached down and gave the cable a poke near the top of the carb.

THE ENGINE IMMEDIATELY DIED! I had dislodged the snagged cable and it retracted, immediately killing the revs. Why didn't the motor continue to run, if only more slowly?

Well, duh. I had been turning the idle screw down repeatedly and, with the cable now free to seat itself properly, the rpm was set too low to keep the engine turning over.

I duck paddled the bike onto the sidewalk, got off and did my best to make throttle and idle screw agree on a favorable setting.

And then I rode home.

My simple machine was now acting normally. Somehow, I had "fixed" it. Exactly how is a mystery. My guess is that it all it needed was a new spark plug.

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