Sportster ignition problems

Wasted spark system. If fuel and electrical is all good/correct it is often the case in these symptoms that motor cycle spark plugs that although looking good and firing outside of the engine are breaking down and will not fire under compression pressures on a power stroke but will fire unburned fuel on the unpressurized exhaust stroke when the plug again fires in a wasted spark ignition system and when so firing the result is a backfire, usually quite loud.

There is probably a small leak in the intake tube to that cylinder. Remove and carefully inspect and reinstall carb and induction manifold.

Check ignition timing. Have you been working on this cycle?

Hi, Anonymous and the usual suspects are:
1. Severely discharged or a damaged battery should have 12.5 volts or more and be able to pass a proper "LOAD" test if necessary, you may have a preliminary reading of 12.5 volts or more but little or zero amperage the battery is faulty and must be replaced, AGM batteries fail in this scenario more so than lead-acid batteries.
2. Check battery terminals for damage or corrosion, check the battery cables at "BOTH" ends for loose, corroded, or broken connectors, "INSIDE" and outside the cable harness, perform connector wiggle test and check cables with an ohmmeter if necessary.
3. Faulty main circuit breaker and or connections.
4. Faulty ignition coil and or connections.
5. Faulty spark plug, oil or gas fouled, wrong heat range or service type, wrong gap, loose in the cylinder head, broken electrode or insulator.
6. Faulty spark plug cables, leaking or broken, internal damage check for spark leakage in the dark.
7. Faulty ignition module, switch, CKP, MAP, CMP, sensor and or any connector in the ignition circuit could have corroded, loose, or broken pins/sockets
8. Burnt exhaust valve or air leak in the exhaust system.
9. Improper valve clearance (too tight).
10. Check for generated diagnostic codes.
For more information about your issue and valuable "FREE" downloads that you will need for viewing or printing please click on the blue links below and for more specific information or questions at no charge please feel free to contact me at [email protected]. Good luck and have a wonderful day.
https://www.hdforums.com/forum/sportster-models/29968-how-do-i-get-it-to-stop-backfiring-thru-the-carb.html
https://www.mediafire.com/file/62dn289vwu580yn/2006_Harley_Sportster_Service_Manual.pdf/file
http://partsfinder.onlinemicrofiche.com/ronnies/showmodel.asp?make=hdmc
https://ownersmanuals2.com/harley-davidson/sportster-1200-low-2006-owners-manual-66462
https://www.6ya.com/ to speak to me personally

sounds like the exhaust valve adjustment is too tight on that cylinder, the one that is popping out the exhaust. ck. and readjust as necessary.

Double check your wiring---On a dual fire coil, the Orange and Black wires will connect together to the negative side of the coil... using a single fire coil, the Orange wire will be used for the front cylinder negative terminal and the Black for the rear cylinder negative terminal ...hope this helps.

"Backfiring" is a pretty broad term depending on where you live. Some people refer to backfiring as popping from the exhaust while others refer to it as the engine spitting through the carburetor.

I'll assume that you're talking about popping out the exhaust pipe. If it does this after you rev the engine and it backfires on the way back down to idle, this is typical of an exhaust system sucking air. The mixture is extremely rich under these circumstances and will not ignite. But, if your exhaust system is sucking air, it combines with the fuel air mixture already there and bring it to an explosive mixture thus the backfire.

You can check you valves but I've always found that if the valves on an Ironhead are too tight, it's extremely difficult to get it started due to the low compression on that cylinder.

Check you ignition timing and points setting. Also, what kind of condition is your mechanical advance in the distributor in? I'm assuming this is an XLH model and not the magneto equipped XLCH.

What type of carburetor is on the engine? Hopefully not the original Tillotson that it came with. If it's an S&S, the low jet should be a 28 and the main jet a 66 to 70.

Ok, due to different terminology used by different people, I'm going to assume that by "backfire", you mean it pops through the exhaust system when you back off the throttle. On stock exhaust systems which use the "crossover" connector to connect the front and rear pipes, the backfire is usually caused by an air leak somewhere in the exhaust system.

When you back off on the throttle, the mixture is usually too rich to burn in the exhaust system. But, if you have an air leak allowing the scavenging effect of the system to **** air in, the mixture becomes combustable and is ignited by subsequent exhaust pulses.

Check your exhaust system gaskets and replace them if necessary. This should stop your problem. Rejetting the carb may be necessary as well.

hi paul here,
the coil on my bike turned out to be the problem after checking wires, connections and plugs. brought a used single fire. tried it out after being told that coils usaully go all bad not just half. have not had the problem since and i was conteplating buying ignition and coil combo for hundreds. good luck