MS460 compression

[Fruecrue]

I have an Ms460, bought it from a friend's uncle, he had a farm and 80 acres, this was his firewood saw.
Stock as far as I know.
182 psi.
Saw is strong, was going to tear it down and port it, but now I’m pondering it.

What say you? Is this normal for a stock saw? Should’ve measured squish as well... but didn’t.

 

[drf256]

Loads of carbon.

 

[Fruecrue]

Loads of carbon.

I’ll need to pull the jug to check the chamber, but so far that doesn’t seem to be the case.

 

[TreeLife]

Someone delete the gasket on it possibly?

 

[Orangeinthebarn]

I would just keep running it. Find a cosmetic good one with a tired piston for a good price and port it

 

[Fruecrue]

I’ll find out tomorrow. Al knows his saws, I’d better pull the jug to be sure.
I put a dual port muffler on it a couple years ago and could have cleaned the exhaust port.....
Hard to remember.

 

[Chainsaw Jim]

It looks like a pretty thick crust of carbon has already been scraped off the inside of the exhaust port. You can tell by all the scrape marks and little chunks that remain.

 

[Fruecrue]

It looks like a pretty thick crust of carbon has already been scraped off the inside of the exhaust port. You can tell by all the scrape marks and little chunks that remain.

Well, there’s been a motion and a second.
Would be foolish not to follow up.

 

[Orangeinthebarn]

It looks like a pretty thick crust of carbon has already been scraped off the inside of the exhaust port. You can tell by all the scrape marks and little chunks that remain.

Good eye Jim

 

[blsnelling]

046/460s have higher than typical compression.

 

[MustangMike]

I was gonna say, my 046 was 175 PSI stock, so it may not be that unusual.

If it runs good, I would leave it as be.

Most of the time you can not delete the base gasket on a 460 w/o cutting the squish. Which is very different than most 044/440s.

 

[drf256]

I’ll find out tomorrow. Al knows his saws, I’d better pull the jug to be sure.
I put a dual port muffler on it a couple years ago and could have cleaned the exhaust port.....
Hard to remember.

See what you can view not pulling it apart.

Jim is certainly correct in his assessment, but so are Brad and Mike. They are typically higher than the 155 that’s usual in other saws. Is only take a .010 to .020 band cut to ouch them into the 200 psi range.

 

[mdavlee]

I had one that was 175 at 3' feet. It was stock best I could tell.

 

[TreeLife]

I like using a lit boroscope for inspection without (complete) disassembly sometimes.

 

[JonCraig]

I don't have a compression gauge, but I have two 1128's. One is stock, the other has a gasket delete. The stock one (obviously) works just like normal. The other I did a gasket delete and it has .022 squish. That small bump (from ~.034 IIRC) added enough compression that the saw will pop up the decompression valve on its own, every pull.

If yours doesn't pop up the decomp valve, I'd suspect (like others in the thread have said) that it's just how it came from the factory. My $0.02

 

[Fruecrue]

Pulled the jug, good amount of carbon.
Round chamber, mahle.
Squish was .029”
Base gasket is .020”
Need to clean the chamber.
Intake and exhaust ports are good and wide.
I didn’t time it. Piston looks excellent other than some carbon.
The plan at this time is to get the squish around .016”-.018”, whether I sand a bit out of the chamber or find a suitable gasket is yet to be determined.
I will also advance the timing.

 

[RI Chevy]

Seems like a small factory squish band. These 460s are good running saws!

 

[Fruecrue]

 

[Fruecrue]

 

[mdavlee]

I'd set the timing on intake, exhaust, and flatten the transfers and call it good.