I will step up and say that there should not be much side play between the rings and the piston lands/grooves, maybe in the range of .001 - .002 clearance.Sorry to jump on this thread, but tried the Chainsaw page to no avail..
Ive just rebuilt a SD 123 and it runs really well for such an old saw made up of parts (309+123+123)
I pulled the muffler after a few mins running and noticed that there is lots of play in the rings, you can rock the flywheel back and forth and the piston moves in the cylinder while the rings are tight against the wall. P&C were off a hardly used 309 and looked like new.
Should there be any up and down movement at all with rings? If so how much?
Thanks in advance!
Compression is really good, 155psi... Saw runs well, cuts and sounds lovely, apart from the tapping! Ill do a squish check now. I could put an aftermrket cheap piston and ring kit on itThat seems like a big gap to me as all rings I have installed over the years fit much tighter in the grooves. I would not recommend running rings with .006 side clearance but if you have no other choice check to see how much compression they can make.
I have a NOS top end on the shelf that I can get measurements on if you need them for comparison.Thanks... will pull the piston and cylinder and investigate.
Thanks so much! Just pulled top end, skirt is a little marked on both sides. Also cylinder has signs of wear from only being run for a few mins since rebuild. Not scored just a little discolouredI have a NOS top end on the shelf that I can get measurements on if you need them for comparison.
If you meant you have .006 traveling the ring land grove on the piston I suspect someone put 47 x 1.2mm ring in when 47 x 1.5mm might be the correct choice.
Also, If you have a knocking it time to pull the top end to find out why.
I’m thinking it looks like you have some scoring or platting gone from the looks of the pictures. I’d use a dental pick or something with a fine tip and run it across the cylinder walls. If the pick doesn’t glide completely smooth across the cylinder walls and piston skirts (IE: feel bumps/ridges), then it’s time to replace clean cylinder and replace piston (or) replace both.View attachment 765682 View attachment 765683 View attachment 765684 View attachment 765685
Thanks so much! Just pulled top end, skirt is a little marked on both sides. Also cylinder has signs of wear from only being run for a few mins since rebuild. Not scored just a little discoloured
I’ve decided to put and new piston and rings on it... does anyone know if the 47mm piston from the 117, 119 and 120 is the same as the 123?
Also. Will the SEM ignition and flywheel swap over. The current flywheel for Bosch ignition has four fins missing and can’t swap without changing the module also..