Smoothing out a rough idle

First let me get a disclaimer out of the way: I am not a motorcycle mechanic. I don't even play one on TV. I've learned a great deal about maintaining my motorcycles from experience--good and bad, frequent experimentation, and from listening to the mechanics who have worked on my Honda and Harley-Davidson motorcycles over the years. Any advice or tips I give on my web site are for free and all responsibility for your outcomes lies with you. In other words, if you misinterpret something I write and damage your machine as a result, don't blame me.

As my esteemed colleagues at Motorcycle Consumer News (MCN) like to point out, restricted air flow is the most common (typical) constraint on motorcycle engine performance. In general, you want to permit air to flow as freely as possible into your cylinders, yet still filtering out contaminants. Thus, you want to use a clean filter with an optimum surface area. I use a K&N Air Filter that I wash and oil at regular intervals.

Regardless of the filter, if you own a bike long enough, you will very likely encounter a situation where the throttle body/air intake becomes partially clogged from gunk that manages to get past the filter or enters via fuel blow back from the cylinder heads. When this happens, the bike may idle roughly.

Recently, my Harley Electra Glide would idle OK until it got warm (not hot).* Once it got warm, the idle would become rough and the engine would often stall. One of the three guys at J&D Cycle in Morrisville, NC (I omit his name to protect his innocence :-) that works on my bike recommended I try throttle body cleaner. I'm passing this tip along to you because it worked very well.

By the way, I don't necessarily recommend the brand in the photo above. It just happened to be the one I first identified in a local auto parts store.

Step 1: Remove the air filter cover. (Photo 2, above right)

Step 2: Remove the air filter. (Photo 3, left)

Step 3: Spray throttle body cleaner into the air intake. The can's instructions say to do this with the engine off. My friendly mechanic suggested I do it with the engine running while at the same time twisting the throttle to open the intake. I followed the engine-on advice. You have to make your own choice on this one. (Photo 4, below)

Step 4: Put it all back together and enjoy an improved air flow (intake).

As always: keep the shiny side up!



*Once my bike's engine got hot, it idled fine.