Bad misfire

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fixer
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Bike owned: nc30/bsab25
Location: beverley, east yorkshire
Bad misfire

Post by fixer »

Carbs refitted ,new vacumn pipe,replaced starter switch.Started bike ran engine to idle,got kitted out and rode out to the countryside.Bike ran great ran hard through the gears up to 100mph no problem,carried on riding about until i overtook a lorry,the bike started misfiring then carried on.Came to a junction set off bike would not go above 3000 rpm,limped back home bike misfiring.Anyone had same problem?I am thinking electrical what do you fellow riders think.I would be very grateful for any replies cheers.Fixer.
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trademe900
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Re: Bad misfire

Post by trademe900 »

Misfiring after getting warmed up? My bet is on coils and plugs.
fixer
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Re: Bad misfire

Post by fixer »

Thanks for the reply trademe900,was thinking the same. :up:
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MexicanGringo
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Re: Bad misfire

Post by MexicanGringo »

I think the speed restrictor has been known to cut in and stay on, cutting one or two cylinders, but don't think you were going fast enough for that.

If not plugs & coils maybe check the jets&passageways for any crud that may have worked its way in. Sounds obvious but also fuel level may have fallen below the main level selection?
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superlite
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Re: Bad misfire

Post by superlite »

Could be many things. Besides the carbs and vacuum hose, is there anything else that you've changed prior to riding it? What did you do to the carbs while they were off?

Could be the reg/rect if you haven't already attended to that?
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trademe900
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Re: Bad misfire

Post by trademe900 »

Maybe your new vacuum pipe has come off at the number 3 cylinder inlet manifold nipple whilst reattaching the tank or something? It can easily happen.

Also Mexican made a good point about the fuel level- can easily happen.

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