038 Magnum normal compression numbers?

[Ranchero50]

Got one from a friend of a friend who thought the air filter was suposed to only be the wire mesh. Needless to say the sparkplug had wood dust around the insulator and it doesn't like to start cold at all. Compression barely made it to 145psi with the throttle wide open after a bunch of pulls.

Recommendations?

BTW, found out that Stihl will send you manuals for saws for free from their website. I got one for my MS310 two days after requesting it.

Jamie

 

[jensen 32000]

145 actual compression (calibrated gauge) is plenty. I hear all kinds of readings from 120psi to 180, but who can actually test their gauge? Every time it gets dropped or bumped it could (could is key) jump a tooth inside the gauge. We have a documented "Calibration Lab" at work, and I can check my guage. That said I have an 044 with approx 120 psi that starts 3-4 pulls sitting for days to weeks, 1 pull warm, and cuts strong. It a little easyer to pull over than a new MS440 but still runs real good. I have 3 low hours 038 magnums, and the old rule of thumb applies, from 009's to 090's, if it (the power head) drops slowly on its own weight hanging on the pull cord, the compression is probably good. Probably your carb is choked with saw dust. Mike.

 

[Ranchero50]

ok, thanks, just didn't want to invest a lot of time in someones saw without getting results. The drop test worked out fine. Owner said he always had to pour gas down the carb to get it started, but three pulls with the choke set and there is fuel in the bore. Like I said the plug was trashed. Getting a new one and filter in a day or so and hopefully it'll come to life easier.

Jamie

 

[blsnelling]

I'd start with a $10-15 carb kit.

 

[Lakeside53]

More interesting than the compression (which is a bit low) is the piston skirt wear. After a bad air filter - you'll hear it slapping at idle... Expect more spit-back though the carb, rougher idle etc but it will likely work o.k.


If the carb kit and fuel filter doesn't solve your problems, look at the impulse hose, then the seals...

 

[jensen 32000]

Also there is the issue of; if the gauge has the shrader valve in the tip or the extention hose. Which again, "pascal's law" states "pressure is equal through out". I own 30 to 40 Stihls, several low hours saws, I have Not seen much past 155 psi and these saws run great and some have less than a dozen tanks through them, What gives?

 

[1953greg]

with my gage w/ shrader valve, 165-170 is bout all i can consistantly pull w/o a decompression valve. my muff modded stock low hours ms440 shows 170-175 and often rips the handle out of my hand. it also rips w/ 20" bar. whs II ms460 shows bout 190-195 and is practically impossible w/o the decomp.

so according to your data, i would say that my gage is bout 15-20 lbs heavy.
i always thought my numbers were surprisingly hi.

i had a 70 chevelle 384 cu in small block cc'd and calculated 10.8:1 compression and i think i remember it showed bout 170-175psi. i cant imagine 2 cycle engines having more than that.

but what do i know.

well, i know i sure would like to have it back

 

[Ranchero50]

Ok, thanks for the interesting replies. I already inspected the fuel and inpluse lines and they were fine. With a new air filter and Bosch spark plug and one turn out on the jets, two pulls with full choke, it started the next pull with half choke. It does buck and spit more than I'd like, but it pulls through wood just like my 041 super. I ended up with the idle jet about 7/8 turn out and it was smooth and started easily warm.

Jamie

 

[Mike mike]

with my gage w/ shrader valve, 165-170 is bout all i can consistantly pull w/o a decompression valve. my muff modded stock low hours ms440 shows 170-175 and often rips the handle out of my hand. it also rips w/ 20" bar. whs II ms460 shows bout 190-195 and is practically impossible w/o the decomp.

so according to your data, i would say that my gage is bout 15-20 lbs heavy.
i always thought my numbers were surprisingly hi.

i had a 70 chevelle 384 cu in small block cc'd and calculated 10.8:1 compression and i think i remember it showed bout 170-175psi. i cant imagine 2 cycle engines having more than that.

but what do i know.

well, i know i sure would like to have it back

 

[Mike mike]

Is 198psi a lot on the spark plug port on my sthil 038 Magnum
It a non decomp. Cylinder it's crazy hard to start
gasket cyl delete and pop up piston. First start is a ***** you have to do a drop start. Insane compression after ran for a while starts pretty easy.