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Nighthawk ST

Modern Bike Rant


And then there are those problems that I've experienced with my own, fifteen-year-old, 46,000 (update: 68,000!) mile bike. There are quite a few, but then it's old and had a hard life of fast immature riding and fairly frequent crashes.

Oil consumption, about a quart every 800-1000 miles. I don't know whether it's from the valves or the rings or what, but I suspect the rings.

Oil leaks, probably caused by high crankcase pressure. Main problem areas are the starter (mentioned above), metal side covers, and valve train cover (the latter mostly fixed by new $45 seal).

Front brakes have become grabby in hot weather. Not sure what the problem is: lever, master cylinder, caliper rebuild time, worn pads, "floating" calipers, ??? Actually, I think I've fixed this problem by simply greasing the lever pivot occasionally. Thanks to Ken at KC Engineering!

Fuel petcock doesn't shut off the flow of fuel completely. Also, fuel cutoff vacuum diaphragm can stick. Further, rough running after prolonged periods without riding, sometimes only a few days. I haven't figured this out yet, my first suspect is some kind of flooding, perhaps caused be the old petcock/diaphragm.

Clunky shifting (1st/2nd), difficulty shifting down to 1st from neutral, missed shifts from 1st to 2nd.

A leaky front fork seal. It's been pretty stable for about 20,000 miles, so I just check the fork oil level periodically and don't worry about it. Perhaps caused by using too much air in the forks. Nowadays I don't really put any air in, just put the bike on the centerstand and equalize the pressure with the outside world. In 2001, some 1000 miles from home, it started leaking big-time, after some rough dirt roads, but a week later the leaking stopped. Love those "self-sealing" seals.

It sounds loud and nasty. The pipes actually sound loud in a somewhat good way (burble at idle, wail at redline), if you like that kind of thing, but the mechanical noise is definitely nasty. Even the later Nighthawk 750s seem to have a raspy loose-cam-chain sound coming from the (air-cooled) motor, perhaps when running hot.

I get quite a bit of midrange vibration from the grips, and from the passenger pegs when cruising on the highway with my feet back. (Fairly comfortable, preferably with the handlebars all the way forward and a tank trunk or bag to lean into.) The rubber engine mounts may not be as supple as in their youth. I've heard this is a classic symptom of carbs that need to be sync'd, as is a (not unfamiliar) lumpy idle. Dirty main jets could also be an issue I suppose, but they looked clean when I inspected them. Too bad it's such a drag to remove/replace the carbs.

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