DISCLAIMER: If after reading this, someone burns his engine valves or manages to get the pushrod off it’s rocker, please don’t come to me to claim damages.
This is one of the things that have been plaguing enfield owners from over half a century. The feature that gives the bullet it’s distinctive thump is also one of the performance bottlenecks of the engine and also a source of racket. Unlike other bikes which use a chain drive to open and close the valves, the enfield uses pushrods which are simply 2 rods which move up and down due to the motion of the cam and in turn open and close the valves. The most common drawback of the pushrods in a bullet is that if they are loose, the produce a lot of racket which only gets worse as the engine warms up. Quite frankly, I was tired of all the racket and even more tired of all the mechanics that “try” to adjust the “tappets” but the noise just doesn’t go away. The last straw was when the last mechanic loosened my pushrods even more and it was almost impossible to ride the back. It was time to take matters into my own hand.
Firstly, “adjusting tappets” is a wrong term because you don’t actually adjust the tappets, you just adjust the pushrods which in turn reduces tappet noise. I had tried my hand on this once before and even got a good setting but I forgot to tighten the locking nut and before I knew it, after revving the engine for a few seconds, the pushrod came off the rocker and I was left with a dead engine.
It took me almost 1.5 years to get my courage back and try this myself one more time. This is a step-by-step guide on what you need to do.
1. Bring the piston to TDC. On the cast iron engine, work the kick starter with the decompressor and wait for the moment when the Ampere meter shows 0. On the AVL engine, work the kick starter with the decompressor pressed till the time the decompressor is fully free. Open up the tappet cover while the engine is hot.
2. Feel both the pushrods and try to rotate them. They should just be free enough to rotate using some pressure from the thumb. If they don;t rotate at all, they are too tight. If they rotate too freely, or move up and down, they are too loose.
3. There are three nuts in each pushrod. The top HEX nut, the middle locking nut and the bottom adjusting nut. First unscrew the locking nut a little while holding the HEX nut in place with a spanner so that you can rotate the adjusting nut.
4. Increase or decrease the length of the pushrod by rotating the adjusting nut so that there’s no play and you can just rotate the pushrod with some pressure. Do this while holding the top hex nut with a spanner.
5. When you feel the setting is just right, hold both the hex and the adjusting nut in place with 2 spanners and slowly tighten the locking nut. This is the trickiest part because it is difficult to hold 2 spanners steady and adjust with the third one. It took me around 2 hours myself to perfect this part.
6. When you are done, just check if the adjusting nut is firmly tightened and if the pushrod setting is right. If you’re a newbie to this, it will take a few more tries.
7. Do the same with the other pushrod.
It is necessary that you do this while the engine is hot. If the engine cools appreciably while you’re doing this, your adjustment will be fine for a cold engine but the racket will start again when the engine warms up. This is what happened with me and I adjusted the pushrods too tight to compensate for the cold engine. After I had put the tappet cover back in, I realized that the kick starter was completely free and the engine didn’t have any compression at all. This was because I had adjusted the inlet pushrod too tight and the inlet valve wasn’t closing completely. I had to open it up again and start all over again by warming the bike. Just check that the kick starter should meet some resistance at a point on it’s way down. Also, adjusting them too tight may burn the valves, so be careful.
The best guide for bulleteers who want to maintain their own bike is Gurunandan’s website. This guy is an ace whom many people look up to for their bike queries. He’s very helpful and replies to your queries by mail(As long as they are valid).
Or, you can just go ahead and buy Pete Snidal’s bullet manual which is now for sale in India as well.