my harley backfires until shutting off after a 65 mile freeway why?

Question

`after i drive home on the freeway about 60 miles stop at a light it is running just fine then it starts to backfire many times until it stops then its hard to restart it starts i go another mile and it starts again and stops and i have to leave it sit folr 35 min to an hour to get it to start again anyone had this before i have a 2000 harley davidson sportster 1200c

Answer 1

i doubt highly u have carbon buildup in the cylinders. my guess is the bike is runnin a bit lean. if when u pull the plugs and they're practically paper white, the carb is set too lean. it'll cause it to run very hot, hot enough to cause pre-detonation; and that is what its sounding like to me...the mix is firing slightly too soon. not good for the engine or the plugs.
leaking carb boots is already ruled out....i had those on my old yamaha; warmed up, the scoot would run at a very high idle, and u dont mention this at all.

i have a very strong feeling that either condition is givin u the hard time. item 1: carb is set too lean. item 2: plugs mis-gapped/incorrect type of plug/too hot of plug. item 3: choice of gas is too low of octane; my sportster runs the best on 93 octane, worst at 87 octane.

another thing i was thinking. if u havent checked/changed the air cleaner for quite some time, a severely dirty air filter will cause a too-rich condition; air flow thru the filter will be drastically reduced. that can easily foul a plug, cause hard starts.

l was just looking thru my shop manual, and under troubleshooting, they mentioned under 'runs irregularly/misses': damaged wire/loose connection at battery terminals, carb float bowl vent closed off, air leak at intake manifold or air cleaner, improperly gapped spark plugs, plug cables in bad shape...shorting or leaking, water/dirt in fuel system/carb, ignition control module, coil or crank position sensor not working right.

there's quite a bit of chit listed in my manual that would need to go thru a process of elimination to zero in on the main cause of ur problem, and without seeing the bike, that makes it even tougher. if u list in detail exactly what the bike does, it would help zero in on the problem quicker. i can tell u from experience that 'cheap gas' makes our bikes run very piss poor. u could ask this on harley chat group under tech support/sportsters, but they will say the same thing...they would need every last detail to be able to pinpoint the problem for easy fix. 'junior' helped me out with 1 of mine last year. hcg is at http://www.harleychatgroup.com

Answer 2

Guardrails coil answer is a good guess, mine would be a clogged pilot jet. this is based upon a similar condition our XL 1200 had . It was fuel starved at 0 -1/4 throttle and was a ***** to start.
Pop the bowl off and clean the jets, its less than a hour and at worst you can rule that out.
Have you looked at your spark plugs? If they are light at the ceramic area that surrounds the electrode your lean, if dark ,too rich, the ideal is a tan color.
Again the extra plug to check for spark is not a bad idea .

Answer 3

I don't work on bikes, but the basic principles are the same. Sounds like the piston tops are getting hot enough to spontaneously combust the fuel/air mixture even when the spark plug is not firing. Could be excess carbon buildup on the piston. This is a typical cause of this problem after a prolonged high-speed run. There are fuel additives available at your local auto part store that can help break up these carbon deposits.

Good luck with your bike woes.

Answer 4

You may have some grit in your carb that is getting pulled up into a jet after a long cruise? That could cause you to lean out, if it's happening at a light ,stopped or low speed it's probably a pilot.
Next time it happens pull your choke out a little bit to richen it up, if that helps it's a sign your fuel starved at low speed/idle.

Answer 5

It could be a bad coil.
A coil on its way out will fire intermittently or not at all when it heats up. Then fire good as new when it cools down.
Keep a spare spark plug handy when you go for a ride. Check for spark when the bike stops running.

Answer 6

BUY SOME OCTANE BOOSTER FROM ANY BIKE SHOP. YOU ARE TOO LEAN... ALSO CONSIDER JUMPING UP A JET SIZE OR 2 IN YOUR CARB. MY 93CI S&S SHOVEL WILL ONLY RUN RIGHT ON 93 AND UP OCTANE AND I THROW IN THE JUICE BOOST TO HELP. CLUE, IF YOUR PIPES TURNED BLUE... YOU ARE WAY TOO LEAN.... IF YOUR SPARKIES ARE DRY BLACK SOOT (UNBURNED FUEL) YOU ARE TOO RICH BUT TOO RICH IS BETTER THAN TOO LEAN. TOO LEAN CREATES EXCESS HEAT AND HEAT WEARS PARTS AND CAN POTENTIALLY CAUSE SOME BAD THINGS I WILL NOT SKEER YA WITH... JUST UP THAT OCTANE AND REJET. I BET YOU CHANGED THE PIPES WITHOUT TOUCHING THE CARB, RIGHT?

Answer 7

IF YOU HAVE ELIMINATED THINGS LIKE PLUGS,COIL,LEADS,FUEL,CARB,BATTERY START CHECKING YOUR IGNITION MODULE AND SENSOR LOCATED BEHIND THE NOSE CONE UNDER THE CARBY. USE A HEAT SOURCE TO SEE IF IT CAUSES THE PROBLEM YOU EXPERIENCED (HAIRDRYER). AND ALSO TRY SPRAYING BOTH WITH FREON COOLANT. IF THE ENGINE DIES WITH ANY OF THESE TESTS CONDUCT FURTHER TESTS ON THE SUSPECTED FAULTY COMPONENT

Answer 8

Sounds to me like you've got a fouled spark plug. Take them both out and give them a look. Most H-D guys I know put a hotter spark plug in the rear jug to combat fouling plugs.

Answer 9

Harley's backfire because of the single-pin crank. Each cylinder only fires on every other rotation of the engine ,trapping unburnt fuel in the exhaust system. I think that you have a tune-up problem. Maybe plugs, air filter, carb adjustment, or just bad gas...

Answer 10

I thought that guys who rode harleys knew how they worked.