Chainsaw Repair

Please help me understand the putty. Is it the volume underneath the piston?  I believe you could get accurate volume at bdc without the putty but then there is no way to measure the underside of the piston at tdc correct?  Unless you did this with cylinder on which is the no drilling thing, drill the piston to let air out I assume?  I have so many questions.

yes, the only reason for the putty is to help find the volume on the underside of the piston itself, when it is at BDC.

yes.

the last one, yes, kind of the idea....but it is not really just to let the air out.   maybe the following will help to picture it using the "drill the hole in the piston crown method."

to get BDC case volume:  with cylinder removed, piston at BDC.  seal the piston skirt to the case deck with heavy grease.  fill the case and underside of piston with a measured amount of oil via the drilled hole. done.

one could measure the oil being put in there with a syringe and a length of tubing.......(buret or graduated cylinder would work too).

the reason for the putty, is just to do all this without trashing a piston.  not really a big deal, but it you are using 'one off' custom stuff, this can get expensive in a hurry.

the volume of under the piston is an additional portion of the case volume.  like in the first photo shown in this thread, the entire piston does not disappear below the case deck at BDC, so the volume of the piston that is above the case deck has to be measured some way is all.

hope it helps.

i will clean up the thread a bit.

reducing the case volume, can gain some rpms.  hope to show just how many as well.