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Ask Jeff Policky Your Own Question
Jeff Policky
Jeff Policky, Motorcycle Mechanic
Category: Motorcycle
Satisfied Customers: 2425
Experience:  Yamaha Gold, Suzuki Gold, Honda Bronze, Polaris Bronze, BRP
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I have a 1981 HD FEXF Fat Bob Super glide that I bought

Customer Question

Hello- I have a 1981 HD FEXF Fat Bob Super glide that I bought in New Berlin Wi. The bike has a tendency to back fire at 25-2700 rpm. This had happened in the "way" past and a mechanic suggested a hotter plug ( linger length, I believe) that fixed the problem. I do not recall the plug name so any suggestions would be fine.
Submitted: 2 years ago.
Category: Motorcycle
Expert:  Steve replied 2 years ago.
you have an ignition problem. a hotter plug is not going to correct that. a "new" plug may ease the symptoms for a bit, but will not correct it.either your ignition system has a fault or your battery/charging system has a fault.we can determine the cause by making a few voltage measurements.measure the battery voltage under the following conditions:- ignition OFF- ignition ON- with the start button depressed.- with the engine at about 2,000 rpm (fast idle)let me know what you find.Steve
Customer: replied 2 years ago.
Thank you Steve! I will have to go out and purchase voltmeter, take the measurements and get back to you. In each of the bullet points listed, what range (s) are you looking for? For many years the regulator on these models cracked and failed leaving me running off the battery until I noticed the tach swinging wildly and I new I had to return home quickly. That does not seem to be the case here. I also have a new battery installed.
Expert:  Steve replied 2 years ago.
I don't give expected readings. I have found it often influences the readings I get back.I understand your comments. I need baseline data to proceed.we can continue when you get back to me with the data.Steve