the basics are as follows mate,the engine draws in the fuel up through the carb jets using a vaccum in the venturi,then the reed valve closes and the piston tranfers the fuel/air mixture up through the transfer ports in the barrel to the combustion chamber,then the piston compresses the vapour and a timed spark ignites the vapour and the vapour burns very fast as it is cpmppessed the rapid expamsion of the burning vapour pushes the piston downwards and drives the con rod whcih turns the crankshaft theat turns you variator and transfers the drive via the belt to the clutch that grips the clutch bell at a certain rpm using centrifugal force and then drives you wheel around.the burnt gases are pushed out of the exhaust port by the new incoming fuel/air mixture in the direction of the exhaust port.so if you have poor speed check these things
1,the engine has enough compression
2,the air filter is allowing enough air into the engine
3,the crankseals and reed petals are seling properly
4,the fuel air mix is neither too weak nor too rich
5,the variator is functioning properly and the rollers are heavy enough to throw the variator all the way together
6,the exhaust is allowing the gases out as fast as the air is coming into the engine.
tell me this does the engine rev fully out if you rev the engine up while the bike is on the stand?
adam bike doctor, May 2010
