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Old Jan 17, 2019 | 09:40 AM
  #11  
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Racepres
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From: Cental, MI
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Originally Posted by 1981 suprglide
wow I don't get it the front cylinder catches the fresh air first
how can it be hotter and why Harley designed a device for
putting air on the rear cylinder it fits on the dressers I'm sure
somebody here has one
While Logic says you have a Valid Deduction... John has it Nailed...
Can't help it goes against what we Deduce... it is a Fact.
Lots of folks Convinced Single Fire Ignition, and Hardened Valve Seats, and Huge Carburetors, and Bigger cams, and Oh yea... Drag Pipes... all work better than anything....
As an aside... I can guarantee and Show you right here in the Yard, that a 1994 FXR that is running rather well, with just a Change to Dragpipes [admittedly not tuned] will foul the plugs within 1/2 a Mile...
Switch Pipes, and [if the plugs are Champions] clears right up and has great manners besides.
Note I did Not specify Stock Pipes!!!!!
 
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Old Jan 17, 2019 | 09:57 AM
  #12  
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From: Honah Lee
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Certain conditions can fowl a plug and high speed heat can coat tip with a almost clear glass like insulator.
Had in happen I a new truck that had the vacuum operated secondary back barrel of the carb that as vacuum dropped, it let a stop drop out of the way and the linkage picked it up.

It was bent at assembly. This made engine lean at high speed. When it started missing, took it in. They spent days trying to fix it. Even called in the factory before figuring it out.
Seen it happen same thing in a FI German car.
 
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Old Jan 18, 2019 | 09:26 AM
  #13  
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1981 suprglide
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these are the ones but however I use ap 985

Autolite 4265, Champion RN12YC, Harley-Davidson 5R6A, and NGK BPR 4ES
 
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