X-NEWS: cerritos.edu rec.motorcycles: 79665 Relay-Version: VMS News - V6.1B1 12/08/92 VAX/VMS V5.5-2; site cerritos.edu Path: cerritos.edu!nic.csu.net!usc!zaphod.mps.ohio-state.edu!moe.ksu.ksu.edu!engr.uark.edu!mbox.ualr.edu!chaos!dave.williams Newsgroups: rec.motorcycles Subject: rec.motorcycles FAQ of 93.02.01 (Part 3 of 6) Message-ID: <35127.89.uupcb@chaos.lrk.ar.us> From: dave.williams@chaos.lrk.ar.us (Dave Williams) Date: 30 Jan 93 20:17:00 GMT Reply-To: dave.williams@chaos.lrk.ar.us (Dave Williams) Distribution: world Organization: The Courts of Chaos * 501-985-0059 * Public Access Usenet Lines: 127 ===================== Q: Can I use a synthetic oil in my motorcycle's engine? A: Motorcycles in general tend to be highly stressed, run hot, are abused when ridden, and tend to be stored for extended periods. These are virtually tailor-made circumstances where synthetic oils can shine. Unfortunately, most modern motorcycles use a "wet" clutch, that is, the clutch runs in oil. (despite how wacko this sounds, it's true) Some synthetics can cause your clutch to slip. If you have a wet clutch and really want to try synthetic oil, give it a try. If your clutch slips you can always drain it and put regular oil back in. ===================== Q: I've been looking to buy a [brand and model name not important]. Several people have told me those bikes have troubles with second gear. How can I tell if this one is OK, and why do they have this problem? A: Second gear problems are the most common of all. They tend to be worse on high-power machines. Typically, the rider doesn't get the gear all the way into engagement, and it pops out under hard acceleration. This typically rips metal off the engagement surfaces, making it that much easier to pop out the next time. Eventually the machine will pop out of gear under acceleration. Incorrectly adjusted clutches, careless shifting, and shifting without the clutch can all cause second gear problems. The fact that you could shift your dirt bike without the clutch is not relevant; your dirt bike probably doesn't weigh 550 pounds, run on pavement, and have a fat tire on the back. ===================== Q: My motorcycle seems to use up chains pretty fast. How can I tell the difference between a good chain and junk chain? A: I wrote an article for Australian Motorcycle News which covered this subject in detail. I've reproduced it here: Years ago chains were considered disposable items. I remember scraping up money for the spring chain and sprocket ritual every year when I was in high school. Sometimes the chain wouldn't make it through the summer, even with fanatic oiling. Every T-shirt I owned had an oil stripe down the back on the left, much to my mother's dissatisfaction. I once had a two-month-old chain on my 175 Kawasaki snap while going 50mph. The broken chain wrapped itself around the swingarm and locked the rear wheel solid, whereupon the rear wheel decided it would lead for a while. By some miracle I came to a halt still vertical, but I have had a paranoid distrust of chain drive ever since. Now what, might you ask, would cause a chain to break like that? It was properly lubricated, adjusted, and running on the correct size (new) sprockets. Chances are that the local motorcycle shop had sold me some ordinary industrial chain instead of motorcycle chain. Such unscrupulous dealings were far more common years ago than they are now. A real chain might cost $30 then, but farm machinery chain sold for a little over a dollar a foot. What's the difference? In its simplest form, the roller chain consists of side plates, pins, and rollers. When properly lubricated, this type of chain will perform acceptably for most engineering purposes. Unfortunately, proper lubrication consists of an oil fog or bath and freedom from dirt, both conditions unlikely on a motorcycle. Twenty years ago some machines still came with enclosed chains, but the enclosed chain died away not because of styling, but because it was a tearing pain in the arse to service the chain or rear wheel with the bulky (and oftimes leaky) enclosure in the way. The oilite-bushed chain assisted the enclosed chain to oblivion. A porous bushing was pressed into the roller and rode on the pin. This porous bushing was impregnated with lubricant and would absorb chain lube too. With a moderate amount of maintenance the bushed chain was satisfactory if not perfect. Since the mid-1960s all "real" motorcycle chain has been of the bushed type. The chain that caused my hair-raising ride was likely of the previous type. In the mid-1970s the "O-ring" chains came into use. These were bushed chains using O-ring seals to keep the lubricant in and dirt and water out. They represent the latest word in drive chain design, being reliable, long lasting, and low-maintenance. Indeed, when run on plastic sprockets, the O-ring chain may need no other lubrication during its operational lifetime. Modern motorcycle chains come in two basic types - those which are endless, and those which use master links. Endless chains came about when engineers realized that most catastrophic chain failures ocurred at the master link. By eliminating the master link, reliability could be enhanced. Unfortunately, endless chains can cause a problem if the sprocket sizes have been changed much; if it is too long or too short, nothing can be done. Endless chains also usually require time-consuming removal of the swingarm for replacement. Motorcycle drive chain contains two kinds of links. Roller links consist of two side plates, two rollers, and two bushings, all a slip fit over the drive pins. Pin links consist of two side plates and two drive pins, with the pins being a tight press fit into the side plates and staked in place for permanence. These links overlap, rollers on pins, to make the complete chain. Most chain is made in inch-based sizes, because the standard chain dimensions were established before much of the industrialized world had adopted the metric system. The basic chain size is given in terms of pitch, which is the on-centers distance between the rollers. The roller diameter is standardized at 5/8 of the chain's pitch dimension, so the common 5/8-pitch chain has a roller diameter of .391 inches. Unfortunately, no such uniformity exists in chain width, which varies a lot, as does sprocket thickness. Running a chain on sprockets which are too wide is usually a feat beyond even the most mechanically disinclined; unfortunately, it is also possible to run a chain on sprockets which are too narrow. The results of this are not good - the chain usually runs to one side of the sprocket, concentrating a majority of the load on one side of the chain, lowering its strength considerably and greatly increasing both load and wear. The loads on a chain are astounding. An average large-bore motorcycle in first gear can easily develop 1500 pounds of pull on the drive chain. The load-bearing area on the drive pins is about .075 square inches in circular contact, in reality, much less. The best-case loading for each pin is on the rough order of 20,000 pounds per square inch! With this kind of load, chain wear becomes less of a mystery. The loads imposed by the engine are only part of the stresses inflicted on the chain. If you watch a motorcycle in motion, you will see that the slack side of the chain does not simply droop. Instead, it snakes and curves in a wavelike motion induced by its tendency to try to wrap itself around the sprocket. Stresses involved can be quite large. This threshing about adds to the relative motion between the pins and links and wears the chain out faster. Motorcyclists often refer to "chain stretch." This term is somewhat misleading. Chains do not actually stretch materially; any load large enough to appreciably stretch a chain would be as likely to snap it right in half. The stretch referred to is the growth in overall length of the chain due to wear in its many moving parts. The chain's pins pull very hard against the bushing walls and most of the wear occurs at those contact points. Loads carried by the bushing/roller contact surfaces are just as large but spread out over so much area that the pressure at any given point is much less than at the pins. In the normal course of events a chain's pins will be worn to their service limits long before the rollers are in any trouble. A chain is ready for replacement when stretch exceeds 2 to 2.5 percent. On a 5/8-pitch chain, this figures out as about .0125-.0156" of slack per pin joint. Measuring each joint with a micrometer is not necessary. For example, a chain measuring 65 inches has reached its service limit when its length has grown to 66.3 to 66.63 inches. As the chain wears, the effective pitch between the links becomes greater. The chain's pitch becomes slightly longer that of its sprockets, causing the rollers to ride up on the teeth and apply pressure where the sprocket is narrow and weak. A properly-designed sprocket is designed to engage the chain's rollers gently, ease them down to the base of each tooth - where the load is taken - and then disengage smoothly and send the chain away. As the chain rides up on the teeth, sprocket wear increases dramatically. It would be nice if the sprocket makers would tell us how much a chain may stretch before it would no longer fit within the design limits of its the sprockets. Unfortunately, most sprockets come bulk packed, or, if we are lucky, they might be blister-packed to prevent them from being beaten up in shipment. Chain wear can be kept to a minimum by keeping it clean and properly lubricated. Gasoline, kerosene/paraffin, and cleaning solvent are definite no-nos for cleaning chain. They can eat the O- ring seals and then hang around to contaminate the lubricant. Wipe any dirt of sand off with a cloth, then apply your favorite lube. Specially-formulated chain lubes usually spray on like a thin oil to better penetrate the crevices and then congeal to better prevent being thrown off. Inexpensive non-O-ring sealed chains require much more frequent attention. On an unlubricated chain the friction between links can cause temperatures to rise to the point where the links can actually weld themselves together, putting a permanent kink in the chain. New chains have a breakin period, and that's when they have special need for proper lubrication. If their pins are well-oiled the loaded surfaces will be burnished smooth, leaving them in better condition to resist wear. Without adequate lubrication the surfaces will scuff and gall, greatly accelerating wear. The chain final drive has come to become the mark of the sporting machine. It is lightweight, mechanically efficient, inexpensive, and compact. Chain technology is still developing, and it's likely we'll see chain drive used for a long time. ===================== Q: My engine has a magnetic drain plug. Whenever I change the oil, it's always covered with tiny metal splinters and spooge. Does this indicate problems in the engine? A: Probably not. The magnet's purpose is to attract ferrous spooge. The gooey mess is tiny iron filings from your cams, cylinder walls, and other wearing surfaces. It's basically the same sort of gick your oil filter traps. Small splinters and pinhead-sized chunks are usually pieces of your transmission's engagement dogs. It's normal to have *some* splinters even on carefully-ridden machines. A lot of them indicates missed shifts or worn shifter components. Pinhead-size or larger flakes usually mean the case hardening is coming off the gears. That's a bad sign. =====================