A Manifold Adventure

The central character in this post, shown below, is the intake manifold for a 1999 Road Star.

In November Mike Harmon and I decided to ride down to the Salton Sea to photograph the hundreds of egrets that winter there.

Near the PalmSprings exit on the I-10, my Road Star’s carburator “blipped” a couple times. It reminded me of the way that carbs act when a bead of water passes through it. It was something I had experience with decades ago, since water in the tanks at filling stations was more common when I began driving than it is now.

We turned onto the long sweeping ramp that transitions to Route 62, then quickly east onto Dillon Road. The carb blipped again a couple miles down the road. Then again. And again.

We pulled off the road and parked on the shoulder. A quick roadside inspection helped us rule out a fuel leak. I began to suspect the fuel filter was getting gummed up by something, that it was partially clogged. We backtracked to I-10 on Indian Avenue, then rode a few miles down the freeway. The carb kept cutting out briefly at various intervals and we gave up the ride after another 20 minutes, returning to our respective homes.

Figuring that the problem was somewhere upstream of the carburator, I replaced the fuel filter. The problem persisted and a few days later I replaced the fuel pump. The problem did not go away. The bike limped around town for several days, while I thought about the problem.

Eventually, I ordered new gaskets and o-rings for the carburator, then pulled the carb. My son Aaron, who has a vast knowledge of motorcycle carbs, disassembled the carb and I dipped it in carb cleaner and rinsed and dried the parts. A day later Aaron put the carb back together, then we reasessembled the bike.

The bike fired up just fine, and we let it idle for a few minutes to let it warm up. But when I rode it onto the street, it was quickly apparent that the problem had worsened. It was coughing, spitting, blipping, and backfiring simultaneously. I made a U-turn halfway down the block, hoping it would limp into the driveway.

I returned the Road Star to its parking space in the garage, and we gave the situation some thought. We had returned the carburator to its original settings and were certain that the rebuild was correct. There was no certainty about how to preceed.

The next day I phoned Brian Erman of Nopork. Several years before I had worked with Brian while on a long contract with the Auto Club. I thought that since he had owned several Road Stars, it was likely that he had knowledge about the problem. I described the symptoms. Brian said he would bet that there was a crack in the intake manifold, since Road Stars tended to develop that problem after 40,000 miles.

After testing the manifold, I drove to the Nopork in Norco for a new one. Brian couldn’t find a stock replacement manifold, but did find a ported one. The ported manifold is supposed to give the motorcycle 5 to 6 additional horsepower by refining the air flow from the carburator to the cylinders.

I bought the ported manifold and installed it. When I started the bike, it sounded like it was running fine, but the tone of the exhaust was different. I rode it around the block, and there was no coughing, spitting, or backfiring.

Because of the additional horsepower, the bike feels different. It feels like it could easily take off from under me and leave me behind. It took a few days to get used to it. I’ve had to learn to be more careful with the throttle.