I have a 1988 Springer FXSTS. I bought it used, and immediately went to work restoring and repairing a lot on the bike, including repainting the engine replacing starter relay, all breakers, the flasher, etc.

I rewired/rebuilt the wiring on the front end and installed Deutsch connectors a few months ago as the turn signals were working intermittently. Wires were falling out/broken between the tanks. I replaced the ignition switch at that time as well because the center post ball fell off--it was the original switch. It would cause the bike to die every now and then as it lost contact. That is all fixed and working as it should.

The bike was quite jerky at low RPM (first or second gear), which was mitigated when 1) I had the SS carb cleaned, and 2) replaced the VOES hose. The ignition module is a HI-4 Crane Cam. The jerky/rough is still slightly there at low RPM after all I have done, but, it is not even half as bad as it used to be. This background I figure would be helpful as I explain what is happening, that others have spoken about here, and here. Dr. Hess has been helpful to me in those forums. BUT, I am still in the middle of diagnosing what this problem might be, and I did not see a resolution on those boards--something I will not do here. If I get it fixed, I will let everyone know.

I have not ridden it much at night--about 3 times. The first time (after I did all I related above) it ran fine. Road home at night, lights on. No problem. The last two times, when I turn the ignition to lights, the idle decreases. This was a sudden occurrence that was evident from the start-up. It also sounds like I am running on one cylinder. The power is diminished greatly, and as I level off the bike throttle, at any given moment, there is continual backfires through the carb. If I open up the throttle, it accelerates, sort of lethargically, but no misfire/backfire. If I turn OFF the lights, everything returns as normal. Lots of power, sound is as it should be, no backfire at all. Lights do NOT dim, or go out. The only thing effected is the power with the backfire through the carb. All lights run as normal. Also, none of this happens when brake light/turn signals are used. Only when lights are on. Before someone asks (as Dr. Hess has in other threads), yes, the jumper was cut. So I have clockwise first position, on, and clockwise second position, on with lights.

• I have checked for manifold leaks using WD-40. No discernible change in RPM. (Passed).
• I checked the Stator for OHM. Nothing grounded out. (Passed).
• Battery: 12.9v output (Passed) I assume from here, that the bat is receiving a charge when the lights are on. But I need to check the bat DCV and the Stator ACV to be sure.

Before I got to the stator and battery charge multimeter test, I thought the ignition module/coil might be the culprit. I pulled the coil and have ran OHM tests on it. It is a single fire Crane--that is three terminal posts.

• Terminal Post Test (primary side): 3.2 (passed)
• Secondary test--terminal to plug side: 9000 (I am not sure this is a pass as most spec out at 10,000-12,000) But I cannot find spec on what it is supposed to be. Sometimes it bounces to 8900. I am not sure, but perhaps this is the cause of the minor low RPM jerky/missing condition.
• Spark plug wire test (inconclusive. Wires force multimeter jump when moved/jiggled. Ordered new ones (ACCEL) just to be sure.

Things I thus plan to do next:

1. I may pull the tanks to trace the white wire from the center post coil to the ignition. I think Dr. Hess says to test that lead to the coil with the ignition on, and with lights on in a DCV multimeter test. So I will need to do that first.
2. Check the ground wires, most of which are near battery.
3. replace the ignition (I have an extra), but also reconnect the jumper and see what happens in position 1.
4. Stator ACV test with bike running of course.
5. battery DCV test, bike running. On, and lights on.

Anything else I am missing? Any thoughts?

 

1 I may pull the tanks to trace the white wire from the center post coil to the ignition. I think Dr. Hess says to test that lead to the coil with the ignition on, and with lights on in a DCV multimeter test. So I will need to do that first.

With what you have described I'd bet your going to find something doing this test.

Good luck WP

 

Sounds like the load of the lights is drawing quite a bit of the battery. You definitely need to do a stator test. On a/c the stator output@2000 rpm should be 33-36 vac and probably around 12-16 at idle. What is the voltage at the center terminal of the coil at Idle with and without lights on..

 

Before you suspect the ignition system...

A couple of quick tests...

Voltage at the battery posts with the ignition switch off?

Voltage at the battery posts with the ignition switch on (engine not running) ?

Voltage at the battery posts while the starter is cranking the engine?

Voltage at battery posts with the engine running?

 

I did 4 tests today. One of them has me baffled. DCV tester set to “20” Battery shows 12.9

With the engine off, and under the present ignition (not changed out) I found this:

1. Batt with ignition on in 1st position: 12.6
2. Batt with lights on, 2nd position: 12.4
3. Tested the white wire lead to center post of coil: -.09
4. Coil test of white wire, lights on: -.09

With the ignition in OFF, I get a reading from same wire: -.12

What in the name of Zeus is a negative number on a DCV test? For my own curiosity, I did an OHM test on all leads to the coil. (Passed).

 

I don't get the reading on the white wire on the coil.. Without battery voltage it wouldn't run.. You need battery voltage at the white wire.. Do the battery readings with it running to check the regulator, 13.9 is a little low, 14.1 is the goal. Check at idle and 2000 rpm.. You still need to ohm test the stator as well as 2000 rpm ac output test..

 

Load test the battery...

 

If I have the meter leads reversed I can get a Neg reading but the .09 makes no sense right now

WP

 

What ignition do you have? Stock, original or what?

 

He mentioned this earlier

The ignition module is a HI-4 Crane Cam

My curiosity is up on this thread

WP