Friday, May 21, 2021

When your old Royal Enfield runs great, then stops

Wrenches are shown adjusting pushrod.
You'll need three wrenches to adjust each pushrod.
What do you mean you only have two hands?!!

I'm no mechanic, but readers often write in to ask for help getting their old Royal Enfield Bullets running.

"It doesn't start!" is the most common complaint. Almost always, this will be followed by "But it was just running!"

It's true. The line between a Bullet running like a champion and not running at all is apparently very narrow.

This leads to dismay. I know.

Because it just happened to me.

I rolled my 1999 Bullet out of the garage, donned my riding gear and carried out my starting drill (turn up the idle knob on the carb, turn on the kill switch, ignition and gas tap, set the piston just past top-dead-center, and kick).

I'd been out of town and away from the motorcycle for several weeks, so I did not expect it to start on the first kick. It didn't. Started on the second kick, though.

Great!

And then it died. This is unusual for my Bullet.

I repeated the starting drill, being certain to see that the gas tap was on and that the spark plug wire was on the spark plug firmly.

All good. Except, this time, when I went to set the piston, the kick start lever encountered little or no resistance at any point.

No compression! An internal combustion engine won't start or run without compression.

"But it was just running!" I complained, to myself. It's unfair!

The Bullet sat there, unmoving and unmoved by my distress.

Sometimes, left standing for a couple weeks, a Bullet can lose compression as oil leaks down from the rings. A dollop of oil into the spark plug hole and a series of dry kicks will often restore compression.

But when I removed the spark plug this time I found it completely oiled, sodden really. This is a problem my Bullet has, but it made it pretty apparent that there was plenty of oil in the cylinder. Certainly no need to add more. I cleaned the plug and reinstalled it.

There are only three ways I can think of for compression to escape from an iron barrel Bullet, if not past the rings: out the compression release (of course) or out either or both the intake or exhaust valve.

If one or both push-rod valve lifters are adjusted too tightly they can open their valve, allowing compression to get away.

I removed the valve tappet cover and checked the pushrod adjusters. With the piston at top dead center you should be able to rotate the pushrods by pressing on them with your thumb.

Both my pushrods were too tight to move with my thumbs. I got out my tools and very, very slightly adjusted the exhaust pushrod (the one furthest forward) so it was loose enough to turn easily. Instructions on how to do this are here.

I checked the kick start lever. Magic! The lever firmly resisted moving past the point of compression. The Bullet has compression!

The motor now started on my very first kick. I put my tools away. I didn't even bother to loosen the inlet valve pushrod. No sense risking clatter unnecessarily. Instead, I went for the ride I had planned.

I can't explain why my Bullet had full compression the first time I started it, or why that compression would suddenly disappear when the motor had run for a few seconds.

2 comments:

  1. The cam follower/tappet can wear a low spot where it rubs on the cam lobe. It may have been adjusted there in the "pocket". If it jumps up to the "high ground" you'd end up too tight. The follower wear depends on the surface hardening, and as an Indian Domestic product there are no guarantees. You'll need to be able to rotate the "T" shaped follower to check this, easiest with the timing cover off.

    ReplyDelete

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