230psi compression?

[Marshy]

Does it seem even possible that a Jonsered 621 could have 220 psi compression with just a base gasket delete (0.030" squish) and a new ring? Seems like BS to me. What's your brain say?

Same guy has a stock Jonsered 80 with 238 psi and is all stock.

 

[andyshine77]

Has the saw ran after assembly? The saw needs to run and cool down before taking a reading, as tge assembly lube will raise the reading substantially. That said yes it's possible to that high of compression, just not likely.

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[5000+]

Pretty normal for the old jonsereds. The base gaskets were real thin, so not much gain with the delete.

 

[KYsawman]

He could have dropped the compression gauge and it is reading wonky.

 

[mdavlee]

Those Jonsereds were high compression engines. I can believe it’s that high. A 930 would come in at 175-180 with squish at .045”

 

[Wood Doctor]

It could simply be a bad compression tester. Some read high and others read low. I'd say this one reads high.

 

[dgb84]

I had a @mdavlee ported 372xpw that blew 225. I sold it to ambull regretfully, but I know he’s still enjoying it.

 

[Marshy]

It could simply be a bad compression tester. Some read high and others read low. I'd say this one reads high.

He said two compression readers are within 2 psi...

 

[mdavlee]

I had a @mdavlee ported 372xpw that blew 225. I sold it to ambull regretfully, but I know he’s still enjoying it.

That saw barely had 200 right after porting. It wasn’t even broken in when I worked it over.

 

[dgb84]

That saw barely had 200 right after porting. It wasn’t even broken in when I worked it over.

It was in my top 2 favorite saws that I ever owned. I had it and a banana infused 562 that would really cut. Here is a link of me running the 562 in some frozen oak. I didn’t run it like it deserved, but it would really rip, even with round chain.

 

[mdavlee]

It was in my top 2 favorite saws that I ever owned. I had it and a banana infused 562 that would really cut. Here is a link of me running the 562 in some frozen oak. I didn’t run it like it deserved, but it would really rip, even with round chain.

It did run good from what I remember of it.

 

[67L36Driver]

I have two unmolested Olympyk 264F that blow 190. [emoji848] And, a third one does 180. [emoji15]. Well used saws they are.

 

[Beavis331]

Very common for that saw to have over 200 psi. Those old jonsereds were a very stout saw. I would worry about it if it wasn't that high.

 

[Marshy]

I can fathom 200+ from a saw that's been worked over. Even 180 on a stock saw... maybe some of the Jonies were factory hot rods but I've never seen a stock saw with no port work blow 200 let along 230psi (doesnt mean it doesnt exist i suppose). And even if it had 180 before a gasket delete I would expect it to pick up 30 let alone 50 psi.
@andyshine77 brings up a great point though. Maybe he checked it with a lot of oil in the cylinder after assembly. That would make the most sense.

 

[Beavis331]

The old jonsereds were in the 200+ range from the factory. Very common to see 220+ on them.

 

[5000+]

Seems like alot of doubters on the subject. These were high compression engines. Domed pistons, lower exports, small.chambers.
The numbers are normal, not due to excessive oil or carbon build up. These were not the touchy high rpm screamers of more modern design.

 

[wcorey]

Not sure about the 621's but the 80's were particularly famous for high stock compression, 238psi wouldn't surprise me at all.

 

[Wood Doctor]

The old jonsereds were in the 200+ range from the factory. Very common to see 220+ on them.

Aha! That explains why the old Jonsereds I saw demonstrated at a GTG in 1978 were being run by factory reps with biceps the same size as Arnold Schwarzenegger's. Decomp valves had not yet been invented.

 

[Lee H]

I have a stock 80 and it will bounce 220 any day. I know the seller of the 621 and
he is as honest as they get.

 

[Beavis331]

Aha! That explains why the old Jonsereds I saw demonstrated at a GTG in 1978 were being run by factory reps with biceps the same size as Arnold Schwarzeneggers. Decomp valves had not yet been invented.

I have a 910 that someone removed the decomp. You gotta be really serious to start that one! Wusses need not apply! The old 80's and 90's were notorious for being hard to pull over.