New (to me) 550 Nighthawk

Joined: 28 Apr 2004 Posts: 62

I found a really pretty 550 Nighthawk, 5400 miles. Starts fine, but runs rich It's been sitting two years, and I noticed that the limiter caps have been removed from the pilot screws. Could this be the source of the rich idle? Is there an easy way to fix this? (Yeah, right.) It's funny because I keep hearing people talk about the Nighthawk running too lean. No problem like that here..

Thanks..

Posted: Thu Sep 02, 2004 3:47 pm

The carbs were probably toyed with by the previous owner. If you have a Clymer's manual for your bike, it should tell you how to sync the carbs correctly, or any dealer shop can do it for you, but it'll cost.

Joined: 22 Aug 2004 Posts: 681 Location: Michigan, USA

A friend of mine just bought a 650 suzuki for his wife. He had a nasty backfire and a lean condition from the factory. He ended up doing just what probably happened to your bike. He had to drill out the caps to get to the pilot screws so he could richen it up. He also had to modify the main needle. Normally there would be an E clip that is adjustable, but not on this one. The reason behind the lean condition from the factory is so it will pass emissions. This engine ( in his motorcycle at least) hasn't changed to keep up with emissions. It's a cheap way for the factory to keep the price of the bike down. the leaner it runs, the less uburned fuel is put out to help pass emissions. As long as your bike runs good and gets decent gas mileage, I'd leave it the way it is.

As for the rich idle. As long as it's just the idle that is rich, you can adjust that with the pilot screws. Your main jet doesn't take over until your on the gas.