compression question

[spydahead]

I have a new 372xpw with 5 tanks of fuel ran thru it. Did a cold compression test, came up with 135psi,sound rite? seems low,think it should come up a bit with the next 5 tanks?

 

[Guido Salvage]

Do you have any way of verifying the accuracy of your gauge? I know nothing of that model of saw, but that seems low to me.

 

[MacLaren]

I have a new 372xpw with 5 tanks of fuel ran thru it. Did a cold compression test, came up with 135psi,sound rite? seems low,think it should come up a bit with the next 5 tanks?

That sounds about right. I think it may come up some more though. To me, that is the best saw ya can have. You like it?

 

[spydahead]

Compression tester is new,checked my other saws,and they check out ok, so i know the comp tester is good. Yes i love this saw,so much so, i dont see myself useing my 288xp very much anymore,to dam heavy.

 

[MacLaren]

Compression tester is new,checked my other saws,and they check out ok, so i know the comp tester is good. Yes i love this saw,so much so, i dont see myself useing my 288xp very much anymore,to dam heavy.

Excellent. They are amazing. I had Eric Copsey port mine shortly after runnin it a while and my goodness man, its unreal. That thing will just flat out rip! Im glad ya like it. The compression does sound about right for new. Im thinkin it'll take what? 8-12 tanks to break it in? Just sit back and have fun! Then, if ya want you can always have yours ported too. Either way, they are IMO the best!

 

[mdavlee]

The 372s have a big squish from the factory and will have compression usually around 150 when broken in.

 

[spydahead]

Thanks guys, i wont sweat it till i get at least 10 tanks thru it,then i'll ck it again.:msp_thumbup:

 

[MacLaren]

Thanks guys, i wont sweat it till i get at least 10 tanks thru it,then i'll ck it again.:msp_thumbup:

Man, that saw is fine. F I N E fine. Glad ya like it!

 

[Zombiechopper]

Husky like to put an 020" gasket in there to give .040" squish. The ones I've seen you just pull that gasket to get a beautiful .020" squish. They make that part pretty simple. Stihls seem to need a gasket but you need one thinner than stock so makes it a pain without a lathe

 

[nmurph]

I think that is probably about right. I bought one with a toasted piston, put a Meteor in, used a aluminum can gasket, set the squish to about .022", and come up with about 160 before it was ever run. It has about 7 tanks through it now. I will try to check the comp tomorrow.
It's headed to Ohio next week for some tweaking.

 

[Sprintcar]

I have found out over the last month or so the wide variances of compression testers. I now have four of them, from a 19.99 Northern tool special to a 6 inch liquid filled 250 psi lab standard pressure gauge. I also bought a digital compression tester at a yard sale, bout as accurate as spitting into the wind. if you have access to a known calibrated 0-250 psi gauge, compare your compression gauge to a known value.

Moral of the story, the 19.99 Chinese piece of crap is just about as accurate as the Lab standard gauge. Only off by about 1 psi at 100 lbs of input pressure. Who'd a thunk it, there again wanna buy a digital compression tester?

 

[2stroked2smoke]

Ya, all my 372's only had about 140 compression stock. With a pop up piston and minimum squish I get about 165-170 now. A ported 372 is tough to beat!

 

[blsnelling]

Ya, all my 372's only had about 140 compression stock. With a pop up piston and minimum squish I get about 165-170 now. A ported 372 is tough to beat!

Mine has more than that

 

[spydahead]

So after i get this thing completley run in, and if the compression is still kinda low,does pulling the base gasket for something thinner make a noticeable difference in compression? can you feel it when you run the saw?

 

[MacLaren]

So after i get this thing completley run in, and if the compression is still kinda low,does pulling the base gasket for something thinner make a noticeable difference in compression? can you feel it when you run the saw?

You have a really nice saw. IMHO, if I were you and didnt know a lot about porting a saw, then I would shoot Eric Copsey a private message and ask him if he can port it for ya. It was the best money i ever spent. He does absolutely beautiful work. I believe he got about 35% gain on my XPW. And it's a true work saw. But then again, there's absolutely nothin wrong with portin your own.
I hope that help's ya man.

 

[mdavlee]

So after i get this thing completley run in, and if the compression is still kinda low,does pulling the base gasket for something thinner make a noticeable difference in compression? can you feel it when you run the saw?

A muffler mod and taking the base gasket out should get a nice gain for you. If that's not enough then get it ported. It wouldn't be a bad idea to put an unlimited coil on there to ease tuning for you if you mod the muffler.

 

[angelo c]

I guess I'm the only one here who would not be happy with a new saw pulling 135lbs. That sounds low to me. I don't remember swapping slugs and ever getting less then 150 for a new P/C with fresh rings. And then again I've never owned a brand new saw.

 

[2stroked2smoke]

Mine has more than that

You probably run a bigger pop up than I do. I wasn't bragging anyway. I was just giving this guy a comparison.
If you want to take out the base gasket, it can only help. It not only lowers your squish, it also raises your intake duration a hair and lower your exhaust duration a hair. If your wanting to do the minimum for the maxmum effect, take out the base gasket.

 

[Chris J.]

The 372s have a big squish from the factory and will have compression usually around 150 when broken in.

The above matches everything I've read about the 372, & the2171, which are basically the same saw. I'd need to read through my notes from tlandrum to see what #s he found when the 2171 was stock.