Misfiring Valk after 60 miles


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Jaxs
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Joined: Sun Sep 24, 2017 10:25 pm
Location: Stow, OH
Motorcycle: 1887 Honda Valkyrie 1500C

Misfiring Valk after 60 miles

Post by Jaxs » Sun Sep 24, 2017 10:34 pm



Valk misfires after 60 - 70 miles (hot). Replaced fuel petcock, vacuum line, checked all plugs (cold only). If I test
plugs after getting hot and during misfire will I be able to see a difference of 1 or 2 plugs vs. the rest. If so, could it be a coil
problem?



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virgilmobile
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Re: Misfiring Valk after 60 miles

Post by virgilmobile » Mon Sep 25, 2017 6:28 am

Could be a coil certainly.Does it misfire at a idle also?My 88 did.
I did identify by idling the bike and pulling one plug wire at a time...Just a inch off the plug..This is where you can hear the loud snapping sound of the spark.I found the center spark was very weak compared to the others.I did just replace one coil.I also verified it was bad by resistance measurement comparing it to the other coils.
The wings also can suffer from fuel starvation causing a poor running engine.Sounds like you touched on that with the exception of the vacuum line that operates the fuel valve and the gas cap vent.Check the vacuum line end where it attaches to the engine.They can harden and leak.Loosen the gas cap when it starts to act up.See if clears.If the gas cap vent doesn't work,a vacuum builds in the tank and fuel starves the engine.

Jaxs
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Re: Misfiring Valk after 60 miles

Post by Jaxs » Mon Sep 25, 2017 9:30 am

Thank you for your response. It never misses until I ride for an hour or so and the engine gets hot. I have checked all plugs at start up and all seem to fire with the same intensity. My intention now is to take the tester with me on a ride and when it starts missing, pull over and test plugs again. Don't know if it'll show anything but I'll try anyway. I had the tank off to replace the fuel regulator and checked the tank vent tube and opening and all seems well. I had tried the
"open gas cap" theory before with no indication of any vacuum in the tank. My only guess is something is causing misfiring after the engine gets hot and I've
tried all suggestions that been given to me - all have been greatly appreciated! I have had all carbs rebuilt and all 12 O rings replaced - the carbs were balanced with the "Valk electronic 6 wire meter" and runs fine until hot. Thanks again!!

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virgilmobile
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Re: Misfiring Valk after 60 miles

Post by virgilmobile » Mon Sep 25, 2017 11:29 am

After it gets hot and starts misfiring,does it continue to misfire when it's brought back to a idle or smooth right back out to a perfect idle.?
Is it misfiring only at a higher rpm under load?

Jaxs
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Joined: Sun Sep 24, 2017 10:25 pm
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Re: Misfiring Valk after 60 miles

Post by Jaxs » Mon Sep 25, 2017 2:53 pm

It will misfire until it's shut off and cools down completely. It does not misfire idling when cool - greatly when hot! I can operate the bike successfully when it begins to misfire by increasing the RPM's by 1000 or so.

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virgilmobile
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83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Misfiring Valk after 60 miles

Post by virgilmobile » Mon Sep 25, 2017 4:06 pm

Great...Easy to check..Get it acting up and pull each plug wire off the plug gently about a inch.You will be able to hear the snap of the ignition.They should all be very noticible.
Here's a video of what they sound like on my 88.


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virgilmobile
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84 GL 1200 I

Re: Misfiring Valk after 60 miles

Post by virgilmobile » Mon Sep 25, 2017 4:13 pm

I guess it would be a good idea to do this when it's cold and running great first so you know what it should sound like ...Then you'll have comparison of before and after.

Jaxs
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Re: Misfiring Valk after 60 miles

Post by Jaxs » Mon Sep 25, 2017 7:35 pm

Great stuff! Now that's mechanics even I can understand! lol
The bike and I are separated by over 100 miles so it'll be a few days before I get to it, but after testing I will post back here.
You've gone overboard posting suggestions and I really appreciate it.
Thanks for all your help!

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virgilmobile
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83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: Misfiring Valk after 60 miles

Post by virgilmobile » Tue Sep 26, 2017 9:13 am

We appreciate the feedback.
Do take a volt meter with you to check the battery volts when it acts up.
Short story..My 88 started to run bad about a hour out of town...A quick voltage test at the battery while it was running showed below 10 volt.Not enough.The alternator quit charging.I let it rest to let the battery recover enough to get me home.
I have sense then attached a volt meter to the bike.
Yes a good battery can recover enough power to run it again...
Alternators can also quit when hot and work when cold.

Jaxs
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Joined: Sun Sep 24, 2017 10:25 pm
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Re: Misfiring Valk after 60 miles

Post by Jaxs » Tue Sep 26, 2017 1:06 pm

Since I just installed a new battery I never gave it, or the alternator, a thought.
Thanks!

Jaxs
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Joined: Sun Sep 24, 2017 10:25 pm
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Re: Misfiring Valk after 60 miles

Post by Jaxs » Sat Sep 30, 2017 7:34 pm

virgilmobile

I don't know what we did (you and I) but I rode the bike almost 120 miles, let it idle until the fan came on, ran it hard and it never missed a beat!!
I'm not totally convinced it won't happen again, but for right now it's great! Alternator ran a steady 13v at idle. Going on a longer ride next Monday
and will keep my fingers crossed.
Thank you again!!



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