Article is from Road Runner and Touring Magazine
Today’s motorcycles are offered with three major types of final drives: belt,chain, shaft. The final drive transmits power from the transmission to the motorcycle’s rear wheel. Each type has it’s advantages, and it’s important to choose the right final drive for your intended types of riding.
I have had all three dive systems on different bikes that I have owned.
Belts are quiet and smooth in operation and don’t fling chain lubricant on the bike and rider, because they don’t require lubrication. A belt just needs a simple cleaning by hosing off dirt. Belts should be checked for cracks and other signs of wear during routine services. At that time the belt tension should also be checked and adjusted if needed. Special tools may be recommended by the manufacturer for tension checking and adjusting.
In general,belt final drives are not used on motorcycles designed for off-road use, because rocks and dirt can get between the belt and sprockets. This causes damage and in some cases sudden rear wheel lock up.
Belts usually have a long service life. For instance, Harley Davidson recommends drive belt replacement at 60,000 miles. However, when it comes time to replace them, it can be a considerable amount of work. For example, replacing the drive belt on a Harley Davidson requires the removal of the swing arm and primary covers. Changing final drive gear ratios can also be difficult and costly. The belt’s length matches the sizes of the stock pulleys. Therefore, if you change pulley tooth counts, the belt will likely need changing too. Belts are not cheap. However,over the life of a motorcycle, the cost compared with the cost of a chain drive machine’s chain and sprocket tends to balance out or even be less expensive.
Chain drive is presently the most common motorcycle drive. Chain drive has low power loss and can handle high torque and shock loads well. Motorcycle chains are sold in two basic types: -O-ring (most common in today’s street motorcycles) and non -O -ring. The O-ring chains retain their lubricant internally because the O-rings seal it in between the side plates. Non O-ring chains require more frequent lubrication and adjustment, and generally don’t last as long as O-ring chains. “Therefore, non O-ring chains are best suited for slow speed and short distance machines, while O-ring chains are well suited to highway motorcycles.
Chains typically require replacement every 15,000 miles or so, although there are plenty of exceptions. If the chain needs frequent adjustment to remove slack, that’s a sign of wear. One way to check for wear is to pull out on the chain at the very rearmost point on the rear sprocket considerably, its a sign of wear and looseness in the links.
When it comes time to replace the chain, carefully inspect the sprockets for wear and hooked teeth. It’s best to replace the chain and sprockets at the same time for longest service life. With chain drive, owners chain change ratios easier than with other drives. Sprocket ratios can be changed to reduce engine rpm at road speed, or increase revs for greater acceleration and hill climbing ability. Unfortunately, chains require more maintenance and have the shortest life span compared with belt and shafts. Special chain cleaning tools and chemicals along with chain lubricants, should be used to maintain the chain and sprockets and extend the service life. Chain tension also should be checked regularly and adjusted according to instructions in the owners manual. Chain life depends on its quality, how it’s cared for, and how it’s used. It’s worth noting that it’s better to keep a chain clean then to over lubricate it, which can cause the chain to attract more grime, wearing out the seals prematurely.
With shaft drive, torque is delivered to the rear wheel via a short drive shaft, much like in a rear wheel drive car. A pinion gear drives a ring gear, to turn the direction of drive by 90 degrees again, like a rear drive automobile. The gear type final drive is bathed in gear lubricant, which is sealed to keep it clean and contained in housing. Shaft drives are quiet and require little maintenance in normal use, and this is probably their best feature. The final drive lubricant level should be checked at every oil change service and changed during major service intervals as listed in the manufacturer’s maintenance schedule. If there is no listing, it’s a good idea to change lubricants every 25,000 to 30,000 miles. Shaft drive cost more initially when the motorcycle is built, and can be quite costly if major parts break, particularly after the warranty expires. Changing gear ratios also can be expensive,and therefore could be impractical in many cases.
Final Thoughts on Final Drives
As you can see, each type of final drive has its benefits and liabilities, which is why all three types continue to be manufactured. Belt drive will transfer 95% of the power applied to it, a chain can transmit up to 98% of the engine’s power,and a shaft drive is around 80% to 85% efficient. These percentages can vary. hen it comes time to shop for that next new motorcycle, consider which type of drive is best for you as part of your buying decision.
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