New saw compression

[Deleted member 135597]

Wanted a baseline for compression readings for my new ms461r. What's an average reading for a saw that's not fully broken in yet? I'm getting about 105 after about 5 pulls. Seems low to me?

 

[jmssaws]

Your Guage is broken

 

[earlthegoat2]

It is typical for a saw to gain compression readings after 5 or so tanks of fuel. I would say if it starts and runs fine (which I imagine it does) then yeah, your gauge is broken.

Do you have any other saws you can use that tester on?

 

[Deleted member 135597]

I will get another gauge. What's a good reading for a new engine? It starts very easily, and runs good but I never ran a saw this big so not sure what to expect for power. I could start it fairly easy without the decompression valve.

 

[Marshy]

Generally speaking, most new saws have 140-150 ish compression. Elevation pending.

 

[Ryan'smilling]

A 461 should be over 160 once broken in. 105 would be way way low. I can start my 460 without the decomp quite easily also, so that shouldn't be concerning.

 

[jmssaws]

I'm thinking 170 on a 461

I rarely see a saw gain much if any from new to broke in. I think when done right that rings seat very quick like in the first few cuts.

If it starts good and idles you don't have compression problems

 

[Gypo Logger]

Does Stihl offer different thicknesses of base gaskets for this saw? If so, I'd get the thinnest or delete it all together.

 

[cgraham1]

I'm getting about 105 after about 5 pulls. Seems low to me?

Keep pulling until the gauge stops climbing. Also, does your gauge have a Schrader valve in the tip?

 

[sunfish]

I'm thinking 170 on a 461

I rarely see a saw gain much if any from new to broke in. I think when done right that rings seat very quick like in the first few cuts.

If it starts good and idles you don't have compression problems

I usually see 10-15 psi.

 

[jmssaws]

I usually see 10-15 psi.

Do you oil the piston and rings when you assemble?

 

[sunfish]

Do you oil the piston and rings when you assemble?

Yes, but where I've seen the largest gains was in new saws, mainly the 346xp.

 

[7sleeper]

... does your gauge have a Schrader valve in the tip?

Best tip sofar!

7

 

[Deleted member 135597]

Here's where I'm at. I trust your guys word that the compression is higher than what I'm seeing but..... I know my air compressor line pressure at work is around 120psi give or take. I took a blow gun and blew into the tester end that threads into the cylinder and the gauge read 125psi. I retested the saw and max reading is 110. Yes there is a Schrader valve in the hose tip and there's one at the gauge to release the pressure. I could let the 110 psi reading sit and it stays there so the only leak source could be the fitting to cylinder connection or the cylinder is only producing 110 psi compression. Again it runs good and has no problem with a 25 inch bar in oak. What gives?

 

[Deleted member 135597]

Also I pulled the dual port muffler cover back off and took a peak, the piston looks perfect, rings look good, but when I put piston at bottom of stroke and look at the cylinder wall I do see some streaks ( scoring). Never looked at a chainsaw cylinder so I'm not sure if it's normal or not. Should the cylinder look perfect like the piston does? Another observation is the muffler cover is a grayish white at exhaust. This is what the plug looks like

 

[Deleted member 135597]

You think there's anyway I could have scored this new cylinder? Right now the high screw is about 1 1/8 turn out. The max rpm I've ever seen with the tach is 13600. I'm using stihl ultra oil 50:1 with avgas. I've run about a gallon of fuel through the saw so far.

 

[Karla]

If you can see scoring, then there is definitely something going on inside the engine, both the piston and cylinder should be pristine on a new chainsaw. If your looking thru the exhaust port with the piston all the way at the bottom of its stroke, then that means your looking at the intake side of the cylinder wall. It will be very difficult to see the intake side of the piston unless you remove the carburetor, and carburetor induction boot to cylinder wall. Scoring on the intake side could be due to a lean mixture or improper carburetor adjustment. If you suspect that you have scoring or can definitely see it, I would recommend taking the chainsaw to a Dealer, unfortunately scoring will Not get better, it just keeps getting worse until the engine won't start. Just my thoughts, and two cents.

 

[Deleted member 135597]

I have no clue how it could have gotten scored but it def looks scored to me. Like I said max rpm I ever saw was 13600. I think I will cut what I need to cut, put the stock muffler and untrimmed limiter caps back in and tell dealer it's not performing and I only have 110psi compression.

 

[Deleted member 135597]

Bins of dead stihls

 

[Big_Wood]

you've only seen your max RPM that high because the stock ignition is limited to that. one thing i found typical of the 461 is intake skirt wear from debree ingestion. weird how the 660/460 could inhale huge chunks and happily put out for years but the 461 gets a little bit of fines and the intake skirt looks like it got hit with 60 grit sand paper. add it to the bin of dead ones and go buy new