Question about Harley Davidson Motorcycles

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Front cyl not firing. Switched plugs, leads, and even a new coil. Still no fire to front cyl on coil. Bike 2006 FXST carb

As asked above

Posted by Anonymous on


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  • Harley Davidson Master
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Hi Anonymous, when checking for spark on twin cam engines the CKP needs to measure the compression bump in order to send the correct signal to the ICM/ECM so always check for spark with either a third plug grounded or lift the end of the plug boot 1/2 " off one of spark plugs that are in the head. and the usual suspects are:
1. Fuel tank empty
2. Fuel supply valve turned off.
3. Fouled spark plugs.
4. Engine flooded with gasoline as a result of over use of enrichner.
5. Fuel valve or filter clogged.
6. Vacuum hose to automatic fuel supply valve disconnected, leaking, or pinched.
7. Discharged battery, loose or broken battery connections.
8. Loose wire connection at coil, battery or plug between ignition sensor and module.
9. Spark plug cables in bad condition and shorting, spark plug cable connections loose,
or cables connected to wrong cylinders.
10. Ignition timing incorrect due to faulty ignition coil, ignition module, or sensors " Manifold Absolute Pressure" "Camshaft Position Sensor" "Crank Position Sensor" "Brake Apply Sensor
11. Engine lubricant to heavy ( winter operation )
12. Sticking or damaged valves or push rod wrong length.
13. Primary cam sproket spline sheared or missing spacer.
14. Security alarm system not disarming.
For a primary suspect please visit the website below: Good luck
Harley Diagnostic Codes 04 to Present

Posted on May 19, 2015


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Posted on Jan 02, 2017

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1. #1 test. Obtain a 12 volt circuit tester, the type that looks like an ice pick with a wire coming out of the handle. With ignition on, hold the tip of the circuit test against the post of the coil, the post that is marked with a + The light in the tester should light up, meaning you have battery power. If you don't have electrical power there, trace back to battery to find out why. If you do have power at that point
2. Moving the the opposite side of the coil and place the tip of the tester again the post marked with a minus. With the key on, crank the engine. The light in the tester should flash. These 2 test have just tested your battery and ignition system. Bill

Posted on Nov 19, 2008

  • 83 Answers

SOURCE: Rear cylinder not firing

The first thing I would do is replace the spark plugs again. You can foul a plug and it will cause you more problems than you can ever imagine. I see you have done all the logical things that I would recommend but I did not see you have replaced the plugs after the 200 miles. You would be surprised at how many times a $2.00 part can cause fits beyond belief.

Posted on Dec 08, 2008

  • 65 Answers

SOURCE: firing on rear cylinder not front

I had a similar problem with my Hinda Cb750 after it sat for years. What i had to do was work my way from the battery thru the electrical system cleaning all the connections along the way to the coils This fixed the problem and get me firing on all cylinders. give it a try

Posted on Jun 28, 2009

  • 2 Answers

SOURCE: i just purchased a 2003 yamaha 1100 vstar with

if it is still firing on the same cly then clean the carbs they tend to gum up after sitting

Posted on Aug 15, 2009

  • 1978 Answers

SOURCE: 92 virago 750. Front

You have to test all the electronics on the bike to figure out if you have a bad CDI box. A CDI box can test good and still be bad. Your problem sounds more like a bad spark plug cap. Unscrew the cap from the end of the wire and take an OHM reading on the cap. If it is higher or lower than 5000 OHMs replace the cap . A plug cap from NGK runs about $5. Replace them both for about $10 it should take care of the problem.

Posted on Oct 04, 2010

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