1969 Triumph Bonneville backfire between shifts - The Jockey Journal Board

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Old 08-31-2019, 12:42 PM   #1
BackPorchChoppers
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Default 1969 Triumph Bonneville backfire between shifts

This just started happening. It's backfiring between 1st and 2nd on hard throttle and again going into 3rd. Any ideas I've checked the timing and carb setting. Bike idles great. Also hard throttle off the line for just a second it acts like it boggs down but then kicks in very quickly. Any ideas?
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Old 08-31-2019, 02:59 PM   #2
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Default Re: 1969 Triumph Bonneville backfire between shifts

Partially blocked jets, idle mix slightly off, leak in intake manifold, or exhaust.
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Old 09-01-2019, 04:47 AM   #3
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Default Re: 1969 Triumph Bonneville backfire between shifts

Is it a backfire through pipes or a spit back through the carb...sound like the pilot system setting is off or partially blocked jets....has it got air filters?
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Old 09-01-2019, 08:50 AM   #4
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It's through the pipes. I'm running valocity stacks.
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Old 09-02-2019, 04:00 AM   #5
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Default Re: 1969 Triumph Bonneville backfire between shifts

Do you have electronic ignition? Load test your battery. I've experienced the ignition advance can go haywire at higher rpm when running with a tired battery.
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Old 09-02-2019, 11:14 AM   #6
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I'm running a magneto so there is no battery.
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Old 09-03-2019, 03:51 AM   #7
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Default Re: 1969 Triumph Bonneville backfire between shifts

Could also be a sign of throttle slide wear they start to pull air around the slides and run slightly weak.
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Old 09-08-2019, 09:53 PM   #8
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Well the exhaust is all tight no leaks and no place to leak. I reset the points gap in the magneto to .014 then timed the mag at 38° BTC. I also cleaned and rebuilt the carbs. I've not had a chance to run it yet. I'll do that tomorrow after I get off work and will let everyone know what happens.
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