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Low rpm almost no load intermittent miss

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51Hog
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Location: Wasilla, Alaska

Low rpm almost no load intermittent miss

#1

Post by 51Hog » Sun Apr 12, 2009 5:13 am

Just started troubleshooting an intermittent miss.
Miss was there before I split the case and did all the work to the bike this year.

Very little load---In heavy city traffic slow speed Just over idle to where engine might build enough speed to shift to second---but might not speed up.
Engine will miss once, then run well for a few seconds, then miss two or three times, then run well for a few seconds....
Totally random.
I can ever so slightly retard the timing while the engine is missing. I can feel a very slight reduction in power, and the miss seems to disappear ----but not always.

No miss at all under load at any time at any rpm.

Pulled the carb and went through it.
Float level is just under 1/4 inch.
Throttle disk fits well and is adjusted properly.
Passages and jets clean.
Slow speed needle will shut down engine both rich and lean.
High speed needle has no effect at idle. Does ritchen system at high speed.
No water in fuel.
Plenty of fuel.
Vented caps
No Vacuum Leaks

Timing is dead on.
New clean points and condenser.
Circuit breaker assembly in excellent condition with the exception of the end play in the shaft .013".

New 12v system and the miss was there before the conversion and after the conversion.

Push rods are adjusted properly.
Compression is great and consistent.
New bushings in the cam chest including pinion and cam.

What Am I missing?????
Dale



john HD
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Re: Low rpm almost no load intermittent miss

#2

Post by john HD » Sun Apr 12, 2009 5:55 am

dale,

try a different condensor even though yours is new.

they can be bad out of the box or the wrong value on occasion.

john

51Hog
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Re: Low rpm almost no load intermittent miss

#3

Post by 51Hog » Sun Apr 12, 2009 5:59 am

Will try another condenser. This will be the third. I have learned to never say never.....

john HD
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Re: Low rpm almost no load intermittent miss

#4

Post by john HD » Sun Apr 12, 2009 6:24 am

dale,

what are you using for spark plugs?

no resistors right?

john

51Hog
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Re: Low rpm almost no load intermittent miss

#5

Post by 51Hog » Sun Apr 12, 2009 6:39 am

Don't remember what they are now, but I am sure there is no resistor.
I will check in the morning.
What plugs do you recommend?
Dale

john HD
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Re: Low rpm almost no load intermittent miss

#6

Post by john HD » Sun Apr 12, 2009 7:29 am

dale,

i used to run harley 3/4's but now i use NGK B6L with great success.

your coil was changed when you converted?

john

FlatHeadSix
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Re: Low rpm almost no load intermittent miss

#7

Post by FlatHeadSix » Sun Apr 12, 2009 3:33 pm

Dale
You might also try a little hotter plug.

a few more choices:
Champion H8C
Champion H10C
Autolite 303
Bosch Platinum 4236 (not sure if this is a resistor, might be)

Remember that on the Harley and Champion plugs the lower numbers are the hotter plugs, I guess that makes sense to somebody but I never knew why they did that.

The Champion H8C IS a Harley #3 plug, if you don't believe it just lay the two side-by-side and examine them closely, pretty obvious they came off the same production line.

I run the H8C Champs, they have always worked for me.

mike

51Hog
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Re: Low rpm almost no load intermittent miss

#8

Post by 51Hog » Sun Apr 12, 2009 6:46 pm

I have been running Champion J12YC plugs.
I will pick up some NGKB6Ls and some H8Cs to see if they make a difference.
I did put in a new 12v coil.
Thanks.
Dale

FlatHeadSix
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Re: Low rpm almost no load intermittent miss

#9

Post by FlatHeadSix » Sun Apr 12, 2009 8:36 pm

Dale, and everyone else, please scratch what I posted above, I must have been on drugs or not had enough coffee this morning when I wrote that.

The Champion H8C, or the equivalent) is the plug I use in the Topper and the Hummers. They work great in those engines but are incorrect for the Pan (although they do work fine in the older 900 & 1000 Sportsters)

Dale is correct about the Champion J12YC, I have been running those in my Pan for years with no problems. They are identical to the Harley 3/4 plug in every respect with the exception of what is written on the porcelain; the plugs Harley is currently selling come from the same production line.

About the heat range; Harley numbers are the OPPOSITE of Champion numbers. Harley plugs are numbered so that the lower numbers indicate the hotter plugs. Here's something from the Champion folks:
"The heat range numbers used by spark plug manufacturers are not universal, by that we mean, a 10 heat range in Champion is not the same as a 10 heat range in NGK nor the same in Autolite. Some manufacturers numbering systems are opposite the other, for domestic manufacturers (Champion, Autolite, Splitfire), the higher the number, the hotter the plug. For Japanese manufacturers (NGK, Denso), the higher the number, the colder the plug."

sorry, Please don't shoot me.......

mike

51Hog
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Re: Low rpm almost no load intermittent miss

#10

Post by 51Hog » Sun Apr 12, 2009 9:12 pm

No Problem Mike,
I know what it is like to not have enough coffee----I live on it.

Just got back from autoparts with 3 sets of plugs.
H10c I see that the H8c is not a good thing, How 'bout the H10C
Autolite 303
NGKB6L

It snowed a little this morning but it didn't stick. Just wet and sloppy in most places.
Might be able to test ride a little later.

VT

Re: Low rpm almost no load intermittent miss

#11

Post by VT » Sun Apr 12, 2009 9:24 pm

Check your spark plug wires for cracks (from air pollution). They can bleed off enough current to shock you if your hand gets near the cracks. Then look in the "troubleshooting" section of the '59-69 HD® service manual and follow the prompts.

51Hog
Posts: 664
Joined: Fri May 20, 2005 7:29 pm
Bikes: 1951 Fl
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Re: Low rpm almost no load intermittent miss

#12

Post by 51Hog » Sun Apr 12, 2009 9:30 pm

New plug wires when I converted to 12v.
No change.
I will look at the manual.
Thanks--
Dale

FlatHeadSix
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Re: Low rpm almost no load intermittent miss

#13

Post by FlatHeadSix » Sun Apr 12, 2009 9:44 pm

Dale
All those plugs I listed above are subs for the Topper/Hummer 2-stroke engines

See if you can swap the Autolite 303 for Autolite 4275 (sometimes listed as just Autolite 75).

If you can't take em back I'll buy them from you for the next Hummer tune-up

mike

51Hog
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Re: Low rpm almost no load intermittent miss

#14

Post by 51Hog » Sun Apr 12, 2009 9:50 pm

No problem Mike--
I do have a set of Autolite 85 that I had for spares.
What do you think about those for the Pan?

john HD
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Re: Low rpm almost no load intermittent miss

#15

Post by john HD » Sun Apr 12, 2009 10:08 pm

dale

just out of curiosity what resistance coil did you install?

i cannot remember what value goes with points and what value goes with an electronic ignition.

john

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