Malossi 166cc/tapping change or rebore?

hi, running my malossi 166 kit on the lml casing with the reed block.  The noise from the engine is getting worse, the noise is like a tapping noise which i would say is from the head? The thing is im not sure which is the best way at going at this, one being dont want to just spend loads of money, if any one has ideas of best way to go about fixing this.  I realise could go have it rebored and fit new piston rings etc, or new kit and start again, or put up with it and hope it does not damage engine.  Scoot is running on lml reed block with 26/26 carb (main jet 122) malossi exhaust, cut crank poarted cylinder, gearing up graded to 200 unit with t5 4th, is on a ducati box which changed other day works well. Its just the scoot don't run like it did. Any help please as just having my mk 1 p200/210 being dynoed money is short cheers daz.