hello i have a 96 300ex and when warming up it make an intermitent clunk sound from the engine. Sometimes it will idle for awile with out a glitch then it will die when i turn around. It is because of the noise it cause the engine to hestitate. i am sure it is mechanical but unsure if it is a valve hitting the piston or what is common for failure.
it runs great when warmed up

any help/recomdation would be appreciated

 

I want to add this is a very used atv. It is not a click, tick, but a clunk then the engine hesistates. When warmed up it runs, idles, and has good power. It is stock no aftermarket parts other than the tires and chain.

 

my 97 300ex does the same thing and i race mine and so i changed the piston it quit it shelf a little and the i said ***** it and i turnd up the Idle and it seem to stop and she can run for ever now idle its the sliver flat head screw by the carb

 

I am planning on doing some mods to it as far as a big bore kit, a stage 1 cam, and a jet kit.i might as well put a new timing chain in it and a high compression piston. anyone have any good setup for these ?