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Motorcycle Discussions => British Bikes => Topic started by: Riderx on May 14, 2009, 11:29:42 PM

Title: won't start backfire
Post by: Riderx on May 14, 2009, 11:29:42 PM

I just had my 69 Triumph 650c motor rebuilt. It actually ran when I pulled it out but was starting to smoke and leaked oil bad. I put the motor back in and it will not start. It backfires through the exhaust like a shotgun blast. I run the boyer and have done all the testing to make sure it checks out. I've also rechecked the static timing, it to lines up. Plenty of spark, gas, and batteryvoltage. Can somebody please give some advice on something I might be overlooking?

Title: Re: won't start backfire
Post by: Justin_Faithfull on May 14, 2009, 11:43:41 PM

Just a thought but could you have timed it 360 degrees out so it is firing on the cylinder with both valves open at TDC?
I would check this first.

Title: Re: won't start backfire
Post by: Riderx on May 14, 2009, 11:56:58 PM

I'm running a single coil with duel outs. It fires both cylinders at the same time. Is there a way without pulling side cover off to see if the exhaust/intake cams were installed correctlly?

Title: Re: won't start backfire
Post by: Rex on May 15, 2009, 08:48:02 AM

Certainly sounds like either a cam timing or ignition timing fault.

If it was mine, I'd strip out the timing chest and redo the cam timings, then reinstall the Boyer components checking as I went.

My hunch would be that someone's put a cam wheel in on the wrong marking (some had three key-ways cut) and that's causing your problems.

Title: Re: won't start backfire
Post by: Riderx on May 16, 2009, 05:52:33 PM

The intake cam WAS on the wrong keyway. Thanks a million Rex.

Title: Re: won't start backfire
Post by: Rex on May 16, 2009, 06:44:35 PM

No problem. I'll just bask awhile in the long distance admiration of my fault-finding skills..... ;)