i have bought new cylinder head as spark plug would not tighten up. it has brand new carb on i have origenal 1 still also.the bike is 2009 model.new air filter.it has good spark.could it need new spark plug, or piston? any ideas would very helpful.Thanks

Paul H, December 2013

It's also needs compression and the valve timing set properly, I take it the engines is Four stroke ?

Adam bike doctor, January 2014

Hi,

An engine needs air, fuel, and spark to run. If you have a nice blue spark at the plug then next check for fuel, if you have fuel getting through, make sure you have air.
If the plug is dry after trying to start the engine you are not getting fuel and should diagnose from there (filter, fuel valve etc). If you make sure all the pipes, connections, hoses and clamps are tight, you should get air (don't forget a vaccum is needed to open the fuel valve).
Don't just buy random components to fix a snag, it gets expensive.

Cheers

westcountry, December 2013