Bike turns over but won't start after riding

I have developed a problem with my 94 FLSTF. I can ride my bike for 8 miles, turn it off and 10 minutes later it will turn over but won't start! If I wait about 20 minutes or so the bike will start like nothing was ever wrong. I don't know if it's my ignition coil (single fire), gas (BP premium), peckcock or carb. My bike will also back fire every now and then.  

Before Joe(Slowpoke) gets here, there's a couple of things to test. When the bike has been shut off, pop a voltmeter on it to see if the voltage is dropping too much (10V is too much). When the engine is hot, the parts rub a little harder, and it needs a little more oomph from the battery to turn it over fast enough. So, a weak battery may turn it over when cold, or cooled off, but, not when hot.

If that's not it, Joe can walk you thru the hard stuff.  

8 miles isn't a measure of how hot the engine gets. Out in the country, it takes about ten minutes to start the bike, ride eight miles at a gentle pace and shut it back off with only the heads and exhaust headers coming all the way up to normal operating temperature. In the city in heavy traffic, 8 miles could take over an hour and already be damaging the oil despite the best efforts of an oil cooler.

That said, what you describe sounds like vapor lock. Some decorative fuel lines allow more heat transfer and should not be used between the cylinders of an air cooled bike. If you have the oem type of thick black rubber fuel line, this shouldn't be a problem unless it's laying against one of the heads.

The occasional backfire under varying riding conditions doesn't tell us anything other than, something could be tweaked a little better. Backfiring is the first symptom of a vast array of minor problems that most people just ignore, if they still have the OEM exhaust.

If the engine cranks more slowly, when it doesn't start, that could be an indication that frbock's suggestion might be a good place to start. If it cranks at full speed, regardless of whether it starts or not, then the problem probably isn't your battery or starter circuit.

A V-twin should never require the starter to push it through more than 3 compression strokes before it fires and runs. The very first compression stroke may be a little slow, if the starter catches it at exactly the wrong spot, but by the time the second compression stroke begins, the starter should be cranking the engine at full speed and not slowing down for the second and third compression strokes. Even if the bike has been setting for six months, it should start that easily. Any time it takes more cranking than that, something is wrong. Is that how easily your bike has always started (hot or cold), before this? Does it still start that easily, when it does start?

regards,
Joe  

My 1998 Suzuki Intruder does the same thing. My battery is less than 2 years old. What needs to be done to correct the problem.

Thank you,