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  #1  
Old 4 Weeks Ago
staniel's Avatar
staniel staniel is offline
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Question What can cause the engine to suddenly misfire?

I put about 40 miles on my '71 XLCH yesterday for my first real ride with it. It was running really well - it was smooth and shifted good and I didn't have any issues at first minus a few pops here and there when I let off the gas a little bit.

But when I was about 3 miles from home it started to misfire like crazy making the ride incredibly choppy and made it difficult to accelerate. I could get into 2nd gear like this but I didn't want to push it to much so I took it slow the rest of the way home. At one point I just pulled over and let it idle for a bit to see if it would idle okay and it did. I think it only misfired under load.

The problem improved slightly as I kept getting closer to home.

What would cause it to misfire like that after riding smoothly for so many miles?

I checked the spark plug cables and they were connected well, I checked compression for the hell of it - was at 140 for both. Could it be a sticky distributor? Crud in the gas tank (it's pretty clean but not spotless)? I'm running 93 octane so I don't think that's the problem.
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  #2  
Old 4 Weeks Ago
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check battery cables
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  #3  
Old 4 Weeks Ago
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Ignition settings may have shifted also. If points. Easy enough to check. If setting OK on points. Check for broken springs on weights, broken roll pin on back of weight holder post cludge.

I'd go the auto parts store and buy me a spare condensor for it also. https://www.amazon.com/Standard-Moto.../dp/B000WJCP5C

Just showing what brand I try and find at the auto parts store. Loose cables like suggested above though is good first check. Loose grounds, etc ......

Edit: forgot to mention since most new members here leave out info when asking something.

If the tank hasn't been cleaned. It will cause this also when running on dregs of fuel on bottom of tank.
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Last edited by rokytnji; 4 Weeks Ago at 15:40..
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  #4  
Old 4 Weeks Ago
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Might have the carb set too rich and it's fouling plugs.
If the plugs are black you need to correctly set the idle mix HOT

They don't call me Ironhead Rick just because I'm hard headed
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40 miles. Did you start out with a full tank of fuel ?
I can go about 100 miles on mine before I have to switch to reserve. Not really all that far. I get about 14 miles on reserve and then I walk.

Assuming it's not out of gas, does the problem go away once the engine is cool ?

If not, that rules out heat related issues.
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When something like this rears it’s head on my bike I immediately suspect electrical/ignition.
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Quote:
Originally Posted by doodah man View Post
When something like this rears it’s head on my bike I immediately suspect electrical/ignition.
+1

When I first got my Ironhead going I had the same issue. The points were brand new but cheap and poor quality. They would not hold the correct .018 gap and a pin hole burned through the center of the tips within 300 miles. I installed good quality points and they now have over 3000 miles with routine cleaning and maintenance.
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Chk & make sure your kill switch wire isn't chaffed anywhere.I had one that was right where it came out of the frame.
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