9. Powerplant
Competitive race bikes are now available with two distinct and very different engine types—two- and four-stroke—that require very different levels of expenditure to rebuild. The reality is that because of the extremely high levels of power output, the new generation of four-stroke race bikes not only requires maintenance at least as often as (probably more often than) current two-strokes but also costs more. Whereas a top end rebuild of a nonexploded two-stroke will cost a couple of hundred dollars, a top end job for a four-stroke race bike is even more. A four-stroke with a season of racing will most certainly need valve replacement and a new piston. If this is not done, chances are it will blow up or worse and easily require as much as a couple of grand to get back to running condition.
We compared a serious but standard two-stroke (Honda CR125R) rebuild with that of a four-stroke (CRF250R). We figured the 125 would need a piston, a ring, a crankshaft, bearings, seals, a piston pin, a pin bearing and gaskets for a complete freshening; those parts added up to $378.92. We estimated the four-stroke would need a complete top end, including a piston, rings, gaskets, valves, valve springs, valve stem seals and a cam chain; those parts run $395. A cam-chain tensioner is roughly another $50. Other four-strokes may run more for parts, but the CRF has the most-frequent rebuild schedule.
There are two quick ways to check the top end of a two-stroke. First, feel how much compression is available with the kickstart lever. There must be a very noticeable resistance, right at top dead center; and if there isn't, steer clear. Second, if you can talk the seller into letting you pull the exhaust pipe, look in on the piston through the exhaust port. With a flashlight, check the condition of the piston. There should be no vertical marks, and especially no shiny aluminum buildup, indicating a previous seizure. Note that this isn't definitive, as the piston can be seized on either side of the port and not visible unless you pull the cylinder; but you can get an idea of the wear and maintenance on the bike by assessing the condition of the piston. Dirt that has entered the engine will also show vertical marks; and a smooth, shiny surface on the front of the piston indicates a lot of use.
On four-strokes, starting is the key indicator. As the engine gathers hours, the intake valves especially will tend to recess into the seats, with the sealing surface of the valve mushrooming out. This will decrease the valve clearance and eventually will cause difficulty in starting because of the tight valves. Also look for blue or black smoke exiting the exhaust when revving the bike. Blue smoke is the result of oil getting into the combustion chamber and indicates worn rings or valve guides and seals; and it means the top end is badly in need of service. Black smoke points to an overly rich fuel mixture and may also signal a worn top end, as the rich fuel mixture tends to wash the oil off the cylinder, speeding wear on the piston and rings. Check out the top end as closely as you can, since it is not cheap to repair.
10. Transmission and Clutch
The internal engine parts are a little more difficult to get a true picture of, but you can get a good sense of the state of things by listening to the running engine and feeling the smoothness of operation of the shifting and the clutch. During your test ride, make sure the clutch fully disengages so you can put the bike in neutral when stopped, and note whether or not the engagement is smooth and progressive. A notchy feel tells of a worn clutch. During your test ride, also check to see if the clutch is slipping by shifting into a high gear then applying a lot of throttle. I can guarantee that a slipping clutch will not heal itself, and you could easily spend $100 or more to replace it. The transmission should shift easily and smoothly and, of course, not jump out of gear or miss shifts. Don't be timid on your test ride, as it's better to have the seller a little mad at you for abusing his bike than to buy a bike that needs $500 or more of transmission work.
The bottom line is that virtually any brand of off-road motorcycle manufactured in the last five years can be a great bargain. The real keys are in how well it has been maintained and how hard it has been used. So be prepared to do a little research on a bike before handing out some major money on a mount that needs even more cash to be a safe and reliable ride. This way, you will avoid painful "buyer's remorse."
Competitive race bikes are now available with two distinct and very different engine types—two- and four-stroke—that require very different levels of expenditure to rebuild. The reality is that because of the extremely high levels of power output, the new generation of four-stroke race bikes not only requires maintenance at least as often as (probably more often than) current two-strokes but also costs more. Whereas a top end rebuild of a nonexploded two-stroke will cost a couple of hundred dollars, a top end job for a four-stroke race bike is even more. A four-stroke with a season of racing will most certainly need valve replacement and a new piston. If this is not done, chances are it will blow up or worse and easily require as much as a couple of grand to get back to running condition.
We compared a serious but standard two-stroke (Honda CR125R) rebuild with that of a four-stroke (CRF250R). We figured the 125 would need a piston, a ring, a crankshaft, bearings, seals, a piston pin, a pin bearing and gaskets for a complete freshening; those parts added up to $378.92. We estimated the four-stroke would need a complete top end, including a piston, rings, gaskets, valves, valve springs, valve stem seals and a cam chain; those parts run $395. A cam-chain tensioner is roughly another $50. Other four-strokes may run more for parts, but the CRF has the most-frequent rebuild schedule.
There are two quick ways to check the top end of a two-stroke. First, feel how much compression is available with the kickstart lever. There must be a very noticeable resistance, right at top dead center; and if there isn't, steer clear. Second, if you can talk the seller into letting you pull the exhaust pipe, look in on the piston through the exhaust port. With a flashlight, check the condition of the piston. There should be no vertical marks, and especially no shiny aluminum buildup, indicating a previous seizure. Note that this isn't definitive, as the piston can be seized on either side of the port and not visible unless you pull the cylinder; but you can get an idea of the wear and maintenance on the bike by assessing the condition of the piston. Dirt that has entered the engine will also show vertical marks; and a smooth, shiny surface on the front of the piston indicates a lot of use.
On four-strokes, starting is the key indicator. As the engine gathers hours, the intake valves especially will tend to recess into the seats, with the sealing surface of the valve mushrooming out. This will decrease the valve clearance and eventually will cause difficulty in starting because of the tight valves. Also look for blue or black smoke exiting the exhaust when revving the bike. Blue smoke is the result of oil getting into the combustion chamber and indicates worn rings or valve guides and seals; and it means the top end is badly in need of service. Black smoke points to an overly rich fuel mixture and may also signal a worn top end, as the rich fuel mixture tends to wash the oil off the cylinder, speeding wear on the piston and rings. Check out the top end as closely as you can, since it is not cheap to repair.
10. Transmission and Clutch
The internal engine parts are a little more difficult to get a true picture of, but you can get a good sense of the state of things by listening to the running engine and feeling the smoothness of operation of the shifting and the clutch. During your test ride, make sure the clutch fully disengages so you can put the bike in neutral when stopped, and note whether or not the engagement is smooth and progressive. A notchy feel tells of a worn clutch. During your test ride, also check to see if the clutch is slipping by shifting into a high gear then applying a lot of throttle. I can guarantee that a slipping clutch will not heal itself, and you could easily spend $100 or more to replace it. The transmission should shift easily and smoothly and, of course, not jump out of gear or miss shifts. Don't be timid on your test ride, as it's better to have the seller a little mad at you for abusing his bike than to buy a bike that needs $500 or more of transmission work.
The bottom line is that virtually any brand of off-road motorcycle manufactured in the last five years can be a great bargain. The real keys are in how well it has been maintained and how hard it has been used. So be prepared to do a little research on a bike before handing out some major money on a mount that needs even more cash to be a safe and reliable ride. This way, you will avoid painful "buyer's remorse."
