kx100 knocking with new rebuild

[DAGGITS]

did a rebuild top and bottom, also put in a new stator. bike kicks over nice and all gears work.  But it is hard to start and knocks when idling.  could timing be off with new stator. and do you have to set the exhaust valve?

[KXcam22]

Thats a tough one to diagnose without seeing/hearing the bike.  First thing would be to do whatever necessary to verify that the timing is perfectly set.  It is possible that is the sole cause but I am not confident that there is nothing else happening.  If the timing is set very wrong it can hole your piston quickly.  The exhaust valve doesn't require setting other than getting the linkages connected correctly.  Please describe the knock sound and it's apparent location.  You can use a screwdriver with the handle pressed to your ear as a simple stethescope to magnify mechanical sounds.  Does the knock continue when you rev the bike?  Are you confident in the crank big end bearing rebuilt or that the top end bearing has not been left out?  Both of these will not be apparent when kicking the bike over but cause exactly what you are describing. Cam.

[DAGGITS]

I have been working 10 hr days and have not had a chance to play with the timing yet but will got to it tommorrow.
the sound continues when it is reved, the sound is a funny sound at first I thought it was the water pump blade scraping and tapping the housing.  , I put in the upper bearing and purchased the crank,bearing and rod as one piece.
 because it is hard to start I am thinking timing , I was very careful but what would happen if I had put the piston in backwards.  thank you for your help and let me try the timing so that I can give you some better information to work  with.

[KXcam22]

With the piston in backwards the ring gap ends could catch in the ports.  It is possible that is what is causing the sound.  I would remove the exhaust pipe, shine a light down the plug hole and veify the piston is correct. Usually there is an arrow that points forward.  This could also make it start funny as the intake timing will be wrong.  Sorry for all the "coulds" but it is hard to tell without laying hands on the engine. Cam.

[DAGGITS]

Thanks I will give it a look.  there was a letter b on the top of the piston and I thought I used the old piston and crank as a reference, but I could have easily made a mistake with all of the parts laying around.