I have taken my motorcycle to the local dealer several times, but have not received much satisfaction. Like most dealers, mine will only recite what he was been told by the manufacturer. Most dealers will not even acknowledge, much less discuss, any other parts or issues.

First, intermittently, when I slow down to s stop, the idle speed on my motorcycle will remain high. When this happens, I have checked the position of the injector butterfly, and it is fully closed. I'm only able to bring the idle speed down to normal by partially letting out the clutch, putting the engine under load. It then idles just fine. I have also noted that many times if I let off the throttle and hold in the clutch the rpm stays higher than a normal idle speed. Finally, my speedometer display and my idle speed are also closely linket. By this I mean that if I come to a pretty fast stop, even though I'm stopped, the speedometer still displays 6 to 10 km/h and the idle is still high, even though I'm stopped. Then, almost immediately, the speedometer goes to zero, and the idle speed goes to normal.

I suggest that you look at the Idle Jet Circuit of your carburettor to correctly adjust your idle speed.

Quote by: ThaiDesign

I suggest that you look at the Idle Jet Circuit of your carburettor to correctly adjust your idle speed.

Thaidesign thanks for the advice, but the motorcycle is a 2002 fuel-injection Harley Davidson Fat Boy. Since I have it I have fitted an K&N air-filter, Vance & Hines Staggered Big Shots exhaust, and a Dynojet Power Commander III (properly setup for this setup). Also I replaced the stock spark plugs with Iridium spark plugs and a set of aftermarket spiral core plug wires.

Hi Bill,

It will maybe sound unbelievable, but your iridium spark plugs and maybe the aftermarket spiral core plug cables are the problem. The electronic fuel-injection Harley-Davidson bikes sense detonation by putting an weak AC signal across the spark plug gap. The spark plug and wire resistance is very important, so I would start by putting the stock spark plugs and spark-plug cables back in. After that, check the Dynojet Power Commander fuel-map and experiment with other fuel-maps for the best performance. Make sure the Power Commander matches the ECM software that's installed on your motorcycle.

Hey Have you cleaned and lubricated all your control cables? Looks like your throttle cable is sticking?

I feel a bit stupid, the Harley Davidson dealer in Bangkok told me also that bike was sensing detonation through the spark plug and the Iridium spark plugs I installed had a different electronic resistance and therefore could create all sorts of problems. I did never take him serious, but now you also say it, I have replaced the spark plugs and the engine is back at it's regular idle speed.