my enfield thunderbird while starting gives a backick with a loud sound like cracker, suggest how to start.?

Answer 1

As with any engine, if the engine pushes back against the starter it is an indication of timing advanced a bit too far. If there is a manual adjustment on the handlebars for timing turn it to retard for starting and slowly advance it as the engine warms up. If not then I suggest you learn how to retard the timing by adjusting the distributor. It may only need one or two degrees difference.
A friend of mine had a bike that was a stinker to start if he advanced the timing to where it ran good, so he kept a wrench in his coat pocket and loosened the distributor and retarded the spark for starting. Once running he advanced the distributor and tightened the clamp. He made a scribe mark as a reference after using a the proper timing procedure!!

Answer 2

Use a different brand of cracker, Nabisco makes a good one.

I'm not so familiar with the enfield that I'd know if it has a retard switch, I know some Harley's do. My Matchless doesn't, neither does my '55 BMW or my '62 Triumph. If it has one, it's because it NEEDS one. Use it to retard the timing while you're starting it, then advance it as needed when you're riding.

Hopefully you know about the tickler on the carburetor, I'd bet you do because if it's backfiring, it's because there's enough raw gasoline fumes in the exhaust to fire. If you don't know about the tickler, you need to push the little tickler button until a little runs out the carb, that'll be enough to start it on the first kick, old British bikes are great on starting on the first kick when all the stars are in alignment. Otherwise, they can be a nightmare. I've had to push mine until I'm wheezing my guts out, so don't flood the thing no matter what you do.

I'd bet your timing's off. Does it have a distributor like my Matchless? Break out the book and figure out how to set it.

Good luck.
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Answer 3

Adjust the valves and set the timing. Part of your combustion is leaking past a valve...either because the valve is too loose or because the timing is wrong.

Answer 4

sounds like it is flooded, or a timing issue...
I would start by changing the plugs and putting new fuel in,