Motorcycle performance

Category: Motorcycle Repair

Any motorcycle, regardless of motor type, can benefit from some basic bolt on parts. Exhaust pipes are one of the most popular modifications. Whether for sound, looks, being lightweight, or just to gain horsepower, aftermarket exhaust systems have many benefits. Some systems are a full system from the header to the muffler and is more popular on cruisers. Sportbikes generally have well tuned headers and gain more performance from slip on exhaust systems. The factory slip-ons are heavy and have to pass sound tests to be quiet enough. Cruisers will upgrade carburetors and air filters to gain power. Sportbikes usually have tuned airboxes that are best left alone, and usually only upgrade to a k+n or uni style aftermarket air filter that flows more air. The carbs on sportbikes are usually as big as they need to be. Ignition advancers can also be used but generally offer little gains and require 93+ octane to be used always. Many bikes are also changing their gearing to drastically increase their acceleration.


While people change to different gears, there are options for lighter weight aluminum and chrome moly gears. These will offer small gains in acceleration, and seem to last fairly long without wearing out. Gearing for acceleration will reduce top speed but is usually worth the exchange. One tooth less or add three more teeth on the back sprocket. Either change will produce about the same amount of change in gearing and should allow the stock chain to be used. If you do both or more excessive changes a new chain will be needed. If you start with sprocket of 16 teeth on front and 42 teeth on the back and decided to change to one less tooth 15 in front and add two in the rear 44. The equation will work like this. Take the new rear sprocket 44 divided by the new front sprocket 15 is 2.933. Then take the old front sprocket 16 divided by 42 is .380. Then take the 2.933 times .380 which equals 1.115. Take 1.115 subtract by 1 and multiply by 100 to get 11.5% which is the increase in torque and acceleration value. This is a substantial increase in acceleration. Now what about top speed? Lets say you have a top speed of 158 mph. The top speed equation is much longer than the last equation and can be approximated by this next calculation. Although not perfect this will get you in the ballpark. Take your current top speed 158 and divide by 11.5 which will equal a 14 MPH drop. AW now you can ONLY go 144 MPH! Too bad your buddies will have given up long before this, as you pull away from them on the interstate at 70 MPH!!! So all is good! Just don’t get carried away and use smaller than 14 teeth on the front sprocket as it will wear out the chain prematurely. This is a cheap modification that will make your bike feel like a whole new bike.