Thank you very much, I will carry out these checks and in case I will replace the necessary,Okay, to answer your questions :
The cam chain is easily checked by placing the alternator rotor on the "T" mark then looking to see if the cam alignment marks are to - gether ~ they won't be .
The cam chain idler wheel is made of hard rubber, as long as NO VISIBLE WEAR , no bumps / cracks/etc. you can re use it .
The valve testing is also simple : assemble the valves, springs and so on then pour some gasoline in the ports, there may not be a drop of fuel leaking past the closed valve into the combustion chanber .
Typically in D.I.Y. jobs you'll see the edge where the valve meets the seat, begin to get damp after a few moments .
Test each valve separately then dry well with a clean cloth or paper towel before testing the other one .
When I said "hand lap the valves" I meant ONLY use the fine lapping compound .
You don't need Machinist's Blue for the home job, gasoline (NOT WATER !) will instantly show if you're good to go or need more lapping .
The pistons will almost certainly have worn ring grooves (called lands) so even if there's no longitudinal scratches / grooves they should be replaced to ensure the job is done to make it last ~ no fun doing all this only to discover next July it smokes again and you can feel the lack of compression in the kick starter .
How you approach the job often depends on your financial situation ~ I'm a Journeyman Mechanic so I can do as much as I want, others have to con$ider the financial outlay .
One last thing : your engine , like all Gasoline engines, burns the fuel, it does not ever "explode" it ~ exploding fuel inside the engine is called detonation or ping and is ruinous to the engine .
for the valves I will try tomorrow what you told me, ok then I better get a new piston and rings and do a job properly, obviously I try to save money but I don't want to do half work and have problems in the short term.
can you tell me instead if in your opinion the base of the cylinder and the head should be rectified in all cases to remove the remaining gaskets and make the surfaces shiny or can it be done with very fine sandpaper or other similar methods?
Thank you very much, I don't want to take advantage of it but you are helping me a lot