after taking apart an engine and cleaning it! followed up for re-lubing it's internal pats with castor oil, do i have to do the break-in process for the engine again?! Thankz!

no you wont have to break in the engine again just might have to give it a tune and thats about it

For me, each time i take apart the engine & clean i will run 1 tank on rich setting first follow by fine tune!

???why? no need. Just run it, it's broken in. taking it apart won't make it any tighter, if anything you will loose the fit that has occured during running it and breaking it in.

Ya.. i know the engine is broken in & taking apart will not make it tighter! However i personally like to run in 1 tank rich setting before any fine tune. just to "prepare" the engine to working condition! Anyway for ur info, when ever i clean my engine, i do remove the carb needles n clean too! Therefore i will set the needles at rich n tune from there!

no need to brake it in thats already done the metal wont change, and if the break in was done properly it should all have seated well and ready for high temp and stress, just be sure to give it a good amount of after run as lubrication is the key on the first start up.
cheers

sensing our friend here take good care of this engines i would run it 10mins rich on HSN just to make sure. tearing engine apart for cleaning scares me a lot.

just like your car taking your engine apart inspecting everything ie piston damage, any debris, bearings, seals for wear etc just getting to know it back to front and making sure its all clean is a good thing and will prolong life.
cheers

another question, i took both bearings out because of front bearing due for replacement. rear is fine with no axial free play. is it advicable to install old rear bearing back with new front bearing?

Is the usage period for both the front and rear bearing same?

Yes, some people do use old gd condition bearing with new bearing. However on the safe side u might want to replace both bearing at the same time! I personally think if both bearing usage period is the same and one of the bearing give way, mostly the other will give way soon or later! just my 2cent!

both bearings are 2 race old but my rear bearing is ceramic. i wont hesitate if its a steel ball bearing. i think i just install new front bearing and hope nothing happen