Compression testing

[bama]

I just finished re-doing two Jonsered 451EV's and tested the compression at 145lbs. This was after about two minutes of running after rebuild(new piston, ring, cylinder cleaning/honing).

Will the compression increase after using it for awhile or is this where is will be? It starts and runs nice and seems to have good power. I cut one piece of 12" ash and it cut nice.

 

[havvey]

compression

i don't know about that modle but 145 is average i like to see 175, saws will run but at 125 and under they are on there way out. I saw a mac with over 200lbs, yes it was an animal a mean one at that

 

[Lakeside53]

I don't count hours, but after 5 tank full of gas and they seem to start peaking out. If I see 145 at the beginning, maybe 155 after a few tanks. The saw will run fine at 145->155.

 

[bama]

They do seem to run very well and the handlebar heat is pretty warm! I plan to cut with them this summer and sell them in the fall. By then, they should be at max compression.

These are the saws that I cleaned and honed the cylinders after piston scoring. Boy, that sure worked great!

Should my bigger saw have higher compression(920 Jonsered) when I rebuild it?

 

[Lakeside53]

They do seem to run very well and the handlebar heat is pretty warm! I plan to cut with them this summer and sell them in the fall. By then, they should be at max compression.

These are the saws that I cleaned and honed the cylinders after piston scoring. Boy, that sure worked great!

Should my bigger saw have higher compression(920 Jonsered) when I rebuild it?

I'm no Jonered expert, but no, the size of the saw has little to do with the compression ratio... if anything the larger saws often have slightly lower compression.

 

[bama]

I'm no Jonered expert, but no, the size of the saw has little to do with the compression ratio... if anything the larger saws often have slightly lower compression.

That is good to know. I hope to get the 920 put together in the next few weeks.

 

[kd460]

Bama, not trying to stael your thread, but if you (or anyone) could suggest where to get parts (cylinder, piston, rings, etc) for the older jonsereds? I have a 510sp that I will eventually need/like to rebuild. Thanks

 

[havvey]

520

Bama, not trying to stael your thread, but if you (or anyone) could suggest where to get parts (cylinder, piston, rings, etc) for the older jonsereds? I have a 510sp that I will eventually need/like to rebuild. Thanks

ebay:jawdrop:

 

[bama]

Bama, not trying to stael your thread, but if you (or anyone) could suggest where to get parts (cylinder, piston, rings, etc) for the older jonsereds? I have a 510sp that I will eventually need/like to rebuild. Thanks

I PM'd you with some sources.

 

[kd460]

Yes, thanks for the info. I'm looking for new old stock cylinder, piston and rings. Been watching ebay for awhile. No luck so far for new. Maybe a pipe dream. Saw runs fine now, just looking into the future. KD

 

[Jonsered Rep]

list of dealers with high stock of jonsered parts

list

 

[kd460]

Jonesered Rep: Thank You!! Two suppliers in my home state! Big help, KD

 

[TwoTurboVolvos]

Curious....Will shaving the cylinder base raise the compression on a saw? I realize that piston,ring,and cylinder wear is what causes compression loss, but by shaving the head/cylinder, the chamber area becomes smaller therefore giving higher compression.....YES? Has anyone ever done this?
Ron

 

[Lakeside53]

Curious....Will shaving the cylinder base raise the compression on a saw? I realize that piston,ring,and cylinder wear is what causes compression loss, but by shaving the head/cylinder, the chamber area becomes smaller therefore giving higher compression.....YES? Has anyone ever done this?
Ron

yes, but..... do a search on hot saws.. Lot's of issues here...if you deck the cylinder, the port timing changes, so you raise the ports, and... now you in a different world.