Hey Gang,

I've got a real problem and mixed opinions from Harley mechanics. My '04 Fat Boy set-up includes the 95ci kit, high compression cast pistons, 251 (midrange) cam, SE airkit, SE Ignition control module (ICM), Mikuni carb and V&H Big Shots.

The bike has been running great until this season. Two problems started this season. First the turnsignal/security module threw a code and needed replacement as the bike would shut down or not start at all. The module was replaced and this problem was corrected.

Second problem: The bike will be running great and then suddenly begin to run like crap. It sounds as though there is pre-ignition. Not just a 'ping' but more like someone dumped a handfull of ball bearings in the crankcase, or there are 3 Stooges in there with hammers!...I'm talking BAD!!!. I am compelled to shut down the bike immediately to avoid engine-valve damage from preignition. The problem starts immediately without warning. It may be a heat-related problem as it usually occurs on hot days and resolves temporarily when you let the bike cool down.

My dealer said it was the ICM and replaced it. A month later, the problem started again. Last Saturday, I was running great for the first 30 miles. Stopped at a light....idle was fine initially, and then suddenly the motor went into the preignition/meltdown mode while I was sitting there at idle. The problem usually occurs while running at speed. On this day, the weather was clear in the low-mid 80's...not a real hot or humid day for the NE. I can't underestimate the horrible, metal knocking sound the motor makes when this happens. Most of the noise seems to be coming from the left side of the motor. It can't be a mechanical problem or it would be doing it all the time...all mechanics agree on this point.

So I'm thinking it's a heat-related malfunction of a component that has something to do with ignition timing. First the mechanics said it was the ICM (BUT... the problem persists with the new ICM!!!). Some mechanics are saying Crank position sensor....others are saying manifold pressure sensor....some say "I don't know". Frankly, I don't think any of them know for sure...and I don't want to end up with a stockroom full of spare, working parts while they try to figure this out on my parts/labor dime. Dealers are reluctant to call the motor company for tech support because the bike was modified (with Harley parts by the dealer of purchase!!!).

I love the bike. The bike runs like a demon when the problem is not occurring...but I can't depend on it. I have a trip coming up...I don't know whether to take the Fat Boy or my Schwinn...I'll probably go farther on the Schwinn.

I am very frustrated and disappointed with the lack of dealer mechanic consensus on the cause of the problem. Can anyone help?? Thanks...

Regards
AlbertG

 

Well, it's hard to diagnose an intermitant problem. Recording it when it happens might help them a lot. Hearing it might make it clearer to them what's happening. Also moving the recorder around as you record may make it clearer to you were, exactly, the sound is coming from.

If you can afford it you might consider getting a SEST. It can record standalone and you can turn the bike on and off while it's set to record, you just can't turn off the bike while it's recording. Keep it hooked to the bike and setup to record. When the problem starts, hit the little button, record a bit, stop recording and turn off the bike. If it's the map or crank position sensor then that will show it clearly. That's rather expensive though. Grab an MP3 player and record it is cheaper.

 

If there is an intermittent problems with any of the sensors, they will throw a code as soon as the signal is outside a certain range. No code, likely no sensor problem. Left side mechanical noise that goes with temperature can mean a lot of things. Loose compensator nut makes a horrible knocking sound idle and off idle and calms down at revs. So does a failing left side crank bearing. Change focus on mechanical stuff is my suggestion.
Get a stethoscope and explore the area around the primary sprocket. If you are in doubt, take off the primary cover and check the comp nut. Even if the nut is tight, the comp can be loose. Try to spin the compensator cover with a firm grip. If it turns you have a stack up problem.