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Intermintent Misfire


mrduck

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04 RT- just did 36K tune- valves, TB sync (twice) oil change. I've picked up a misfire when at part throttle, and not consistently, at around 3500, runs great at full throttle,sometimes rough idle. Siphoned all the gas out then pulled tank off and dumped what little was left out on driveway, saw what looked like water drops in fuel! Buttoned it back up but still have the intermintent miss, tried new primary plugs, Autolite this time, now I'm stumped! Could the fuel filter be holding some water or am I missing something else?

 

 

 

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If you're concerned about residual water in the system, throw a half pint of Methylated Spirit into about 2 gallons of petrol and go for a ride. If and when it stops misfiring, top up the tank with your regular fuel.

 

We get so much water in our fuel here during the wetter, more humid months, I throw a half pint in about every fourth tank or when needed.

 

I'm not saying that this is your problem but I haven't removed the fuel tank off a bike for water issues in over 35 years.

 

Linz smile.gif

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Don, water in YOUR tank??? Damn! and you live in the arid high desert!

 

There is truly no hope for the rest of us. All our tanks at sea level must be filled to the brim with water... wave.gif

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If you changed your plugs out, you could have one bad plug. If you still have the old ones, pop them back in to see if it makes any difference.

 

Back to the Future...

 

Linz smile.gif

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Thanks, changed the primary plugs after this started, gonna try the secondary ones next. If there's two plugs per cylinder how can both not fire at the same time causing the miss? Or am I still missing something?

 

 

 

lurker.gif

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Thanks, changed the primary plugs after this started, gonna try the secondary ones next. If there's two plugs per cylinder how can both not fire at the same time causing the miss? Or am I still missing something?

 

Either one not firing is enough to cause a noticeable unevenness. I had a bad plug wire on one of my secondaries that caused an intermittent miss. The only way I could really tell was putting an old-fashioned timing light on the wire, and I could see that it would skip a flash occasionally. I don't think this method works on the primaries, due to the coil-on-plug design.

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Thanks both of you! Are the plug wires and the coil connected or are they two parts? Tried new plugs but found out the Autolite secondary plug is silghtly bigger on the outside so none of my sockets will fit up in the engine so gonna order new ones from the dealer and try that. dopeslap.gif

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Thanks both of you! Are the plug wires and the coil connected or are they two parts?

 

The plug wires disconnect from the coil, but it's an "interesting" fitting. Pay attention to what comes out when you take it off.

 

BTW, if you're having this problem, your secondary plug will likely be quite dark.

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FOUND IT

Bill, you were right on! Changed the secondary plugs and cured the misfire and rough running- also found out that Autolite plugs do not fit in the secondarys, too big to fit the wrench so could'nt fit up in there. Even tried to grind the outside of the plug flats to fit! Don't bother to try, good thng they were cheap plugs dopeslap.gif

 

 

 

Thanks and see ya in DV wave.gif

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