Service
SERVICE
Slippery problems
I will be moving to Florida soon and I’m concerned with keeping my '84 Honda Nighthawk S running as cool as possible. Are there any aftermarket oil coolers with a larger oil capacity that will fit this bike? Is it possible to plumb in a second cooler?
Another concern I have is with the oil light coming on during hard stops. It illuminates just before the bike stops moving and sometimes stays on as long as a second and a half. Will this momentary loss of pressure cause any harm to my engine? The oil is at the proper level according to the shop manual.
Redge A. Cromwell Anchorage, Alaska
No one currently makes oil-cooler kits to fit the Nighthawk S. In fact, most of the companies who once sold motorcycle oil coolers have ceased doing so. The demand for them dried up when the hike manufacturers started including good oil coolers as standard equipment on most of their highperformance models. And according to the company that was one of the foremost names in oil coolers, Lockhart, the Nighthawk S already is fitted with a sufficiently large, capable cooler. There would seem to be no need, then, for either a larger or an additional oil cooler.
There might, however; he a need for additional oil. The tech people at Honda acknowledge that the oil light on some Nighthawk S models will momentarily come on during hard stops as the oil in the sump sloshes forward, away from the pickup. They claim that no damage results when this occurs, and recommend that you help remedy the condition by slightly overfilling the crankcase (by a halfquart or less). They also suggest that during the extremely hot weather you 're likely to encounter in Florida throughout the summer months, you use heavier oil (20 W-50 TV. the usual I0W-40). And as a further hedge against the light coming on, they say you might consider setting the idle a hundred rpm or so higher than the idle speed recommended in the manual.
Knock, knock. Who’s there?
I have a 1979 Suzuki GS1000L that has a knock at idle once the engine is fully warmed up. When the rpm is allowed to drop to idle ( 1000 rpm), an audible, metallic knocking develops. If I gradually increase the rpm, the knocking will begin to diminish around 1300 rpm and is completely absent above 1400 rpm. The oil light functions but never comes on or even flickers when this happens. The bike has 6000 miles on it, the maintenance schedule has always been strictly adhered to, and the bike has never come close to being ridden hard. I have always used Pennzoil 10W-40 oil, and there has never been any abnormal appearance to the used oil or filters. The bike has always done this, and the dealer discounted it as being no problem, but could offer no explanation as to what was causing it. Well, it seems to be getting progressively worse now. Any suggestions?
Dave Campbell
Bozeman, Montana
Accurately troubleshooting noise-related problems is tough enough when the mechanic can actually hear the noise in person; when he can't, the task becomes next to impossible. So, there's no way for us to determine if the noise you describe is the result of something major, like a worn bearing, or a collapsed or worn piston skirt.
Chances are, however; that because this noise has been present since the bike was new, it is not the result of any component failure. Instead, it is probably nothing more than a primarydrive rattle, a fairly common occurrence on lOOOcc Suzukis. The noise is indirectly caused by the small amount of clearance between the teeth of the primary drive gear on the crankshaft and the primary driven gear on the clutch hub, and also by the clearance between the tangs of the clutch drive plates and the slots they fit into on the outer clutch hub. When the engine (just about any engine, not just this one) is idling, its speed is not constant; it is sped up ever so slightly every time one of the cylinders fires, and it slows down slightly in between. This rapid succession of speed-ups and slow-downs can cause the primary drive gears to emit noise as the gear teeth take up their backlash first in one direction and then in the other.
And the entire package of clutch plates can make a similar back-and-forth rattling in the clutch hub.
When the engine is running much above idle, or when the idle is sufficiently fast and smooth, audible rattling noises usually are not produced, simply because the rpm fluctuations are too small or dose together. But if the idle is too slow, or if the four carburetors have not been properly balanced and synchronized, the idle can be just erratic enough to exaggerate the normal idle-rpm fluctuations, resulting in a rattling that sounds like serious engine damage. And as the bike racks up miles, the tangs on the clutch plates get hammered enough to increase the amount of slop they have in the clutch hub, resulting in even louder rattling.
Our advice, then, is to go to the best motorcycle repair shop in town and have them tune your engine, placing special emphasis on idle speed and carb balance. That may be all you need to put an end to your engine knock.
An engaging question
I’ve either owned or ridden a total of about a dozen different bikes, from brand-new to four or five years old, and they’ve all had the same annoying shifting characteristics. If the bike is standing still, it usually won’t change gears, especially if the engine isn't running. A couple of times I ended up stopped in fifth or sixth gear because I had to make a panic stop, and found out that it's a real pain to get back down to first when the bike isn't moving. Why is this? I never encounter any prob lems like this when I drive standard shift cars.
Denny Rounds Rolla, Missouri
That's because the transmissions in standard-sh~fl cars use a different type of engagement mechanism. In both types, changing gears does not involve the actual meshing and unmeshing of gear teeth; all of the teeth on the individual gearsets stay meshed with one another at all times (with the exception of reverse in automobile gearboxes), and shifting is accom plished by engagement mechanisms that essentially lock the appropriate gearsets together while allowing all the others tofreewheel.
In a car transmission, toothed engagement rings lock the gearsets to gether after a series offriction rings equalizes any speed differences be tween the two affected gears. These engagement rings slide into place over fine-pitch teeth that have tapered lead ing edges, a design that also allows almost foolproof gearchanges when neither gear is moving, which is the case when the car is stopped and the clutch is disengaged.
A motorcycle transmission, on the other hand, uses lugs or pegs, called engagement "dogs. " to lock the se lected gearsets together. These dogs are quite large and coarse in pitch (usually only four or six dog segments per gear), and are designed so they are a relatively snug fit in the slots or holes or mating dogs into which they must fit. The tight fit is necessary to mini mize driveline backlash. As a con sequence, when neither gear of a mating gearset is spinning (which oc curs when the bike is stationary and the clutch is disengaged). chances are that the affected gear dogs will not be perfectly aligned with their mating dogs or engagement holes. Thus, any attempt to sh~fl is likely to be un successful until the bike is rocked back-and-forth slightly (while a slight pressure is maintained on the shift lever) to cause sufficient change in the dog alignment for engagement to occur.
