Why is it that if you over bore some 4 stroke engines the performance gained is more than what you would expect with the minor increase in actual displacement. As an example a YZ250F with a 2mm larger piston gains only 13cc in displacement yet will likely gain a few horsepower throughout the rev range with no other modifications. The gain actually comes from the larger bore"unshrouding" the valves in the cylinder head allowing for increased air flow. The 5 valve head is especially bad due to the crowding. All the power from a 4 stroke is in the head.
Wow! Attention All you Restoration Guys ! We now offer in House Wet Vapor Blasting for the Ultimate In Surface Finishing. Coming first week November!
Wet Vapor Blasting was originally developed by Rolls Royce to clean delicate turbine blades. With wet vapor blasting you can clean years of oxidation, corrosion, rust, grime and tarnish out of the tightest places while leaving a beautiful long lasting smooth oem satin finish. No other process compares when it comes to not only cleaning but surface finishing parts for a rebuild. You can also clean and restore most plastic and rubber parts. See below for examples !
Had a customer with a 500cc street bike who wanted to put a 2 tooth smaller rear sprocket to increase his top speed by approx 10km per hour. I explained to him that it may do nothing as with everything else being equal top speed is simply a function of how much horsepower your engine produces. As that isn't changing, chances are that gearing is not going to help assuming his top speed now is at approx where his bike is producing max hp.
Pistons always have directional arrows on them showing you which way to install them. Most times the arrow point to the exhaust but there are some weird exceptions (towards PTO, etc) and you need to check before assembly. One obvious reason is locating pin location for 2 strokes and valve size pocket on 4 strokes. There is another reason. The wrist pin is often offset to lessen piston side thrust to reduce wear.
Many manufacturers has built in fault codes to alert of any problems with the EFI sensors that tell the ECU how much fuel to inject at different rpm and load. Most engine sensors emit some noise in their signals and the problem is this value tolerance that the fault code looks for has to be large enough not to trip a false fault code due to noise but also small enough to know when the sensor is causing a problem. To avoid customer complaints generally this tolerance is on the large side so some performance problems can go unnoticed.
We see a fair number of off road bikes with premature engine wear from dirt ingestion. One often overlooked problem is the air filter cage. Many times these cheap plastic cages warp which causes the air filter to not seal tight against the air box. A good solution is to replace it with an aluminum aftermarket unit. Twin Air is one brand that offers this solution.
I have been involved in mechanics and motorcycling from a young age. I formed Cycle Improvements in 1981 and still have the same passion to learn today as when I started. Hope you find this blog interesting and educational.