Backfiring before starting - 71 Johnson 20 HP

[Wingshooter]

I have an electric start 1971 Johnson 20hp that is backfiring (single loud pop).<br /><br />When I turn the ignition the motor will crank and then backfire once. After the backfire, I turn the ignition and she fires right up and runs like a champ. <br /><br />It only backfires once before it starts, never when its running.<br /><br />Put in fresh sparkplugs and both have spark. <br /><br />Any recommended fixes?<br /><br />Thank you,<br /><br />James

 

[jack bowman]

Re: Backfiring before starting - 71 Johnson 20 HP

My guess is improper timing. Worn spark plug insulators could also cause it but you replced the plugs<br /><br />My old rude (1965-33hp) has been doing the same thing and the local mechanic is checking the timing for me now