RS250
Free Horsepower Tips

Check Rear- Wheel Alignment--a straight chassis will track the best and roll down the track the fastest with the least amount of rolling friction. This "free" horsepower will show up on the dyno!  Use the string method or simply look down the chain run to see if this is straight.

Chains and Sprockets--replace chains and sprockets often.  I have seen as much as a 2-3hp loss due to a bad chain.  Non-O-Ring chains are cheap anyways. Clean and lube your chain after every session (practice, qualifying, and after the race).  Use a good chain lube. I  like to use Castrol Chain lube. It looks and works like the chain lube that comes on a brand new chain. Also, it makes sense to use aluminum rear sprockets. They do wear faster, but they are much lighter.  Any HP increase here will show up on the dyno.

Air Filter--wash or replace often.  There is a lot of dust kicked up by other riders and this all gets stuck on the air filter.  If your rules allow, replace with a low-restriction foam air filter.  When oiling your foam air filter, use as little as possible, but do get adequate coverage. Any HP increase here will show up on the dyno. Always use an air filter!

Front Brake Drag--quite a few RS250s I have seen have excessive front brake drag.  Place bike on suitable front stand, and spin the front wheel.  Some I have seen will not even spin 2 revolutions.  A real GP bike will spin at least 10-15 full revolutions.  This is totally lost horsepower, in effect, you are riding around with the front brakes on.  You will notice a higher top speed when corrected, and since this is your front wheel, any improvement here will NOT show up on the dyno.  Look closely to determine the exact cause of your front brake drag.  Possible sources include bent rotors, wheels, improper caliper alignment (you can use very thin shims to adjust this), dirty caliper pistons, dirty or bent pad retaining pins, or incorrect front axle alignment. 

Throttle Adjustment--this is simple. Remove the airbox lid and air filter.  Twist the throttle grip and make sure the carburetor slide opens fully.  Adjust as necessary.