ms170 compression

[anlrolfe]

 

[rd35]

Well....looks like I'm gonna have to order me a side tensioner kit! Nice video! Learnt somethin' new today!!!

 

[anlrolfe]

Side tensioner is SOooooo Sweet

 

[Nathan Graff]

Now, I'm going to have to pop the bar off of the saw, and see if that will fit. I know I'll have to drill the hole though. Side cover doesn't come with one in it. I was actually wondering about getting the side and screw, etc for the tensioner for a 181 on it.

 

[MOOSETRAX]

So, I took the muffler and the carb off the saw. The impulse hole on the carb was plugged. So, I cleared that out, and cleaned up the mating surfaces. The piston and rings were fine. Put the saw back together. It started on the 6th or 7th pull. Really good considering that if the saw had no gas in the line, it would be a half hour ordeal to get it going previously.

Seems to be cutting faster with the muffler opened up, and the newer carb tuned in.

Hey
Though Older thread, my 170 starts brief & dies, shows 130psi compression @ closed throttle. I cleaned the carb. I see good spark, Piston seem fine though not sure. I wonder what setting that screw in carb is supposed to be at (under the cover). It loosens by turning clockwise mine is set at roughly 12 full turns. I guess that the only adjustment at the carb. Any replies appreciated.

 

[MOOSETRAX]

NVM found a manual & says bottom out (ccw) & 2 turns cw for standard setting. PDF Manual here if anyone needs..
https://static.stihl.com/api/BaOnli... 05ZBA/0458-207-8321-B_ZBA_05_02.pdf

 

[Vintage Engine Repairs]

Can’t remember the setting but 130 psi is low. I’d suggest taking the muffler off and seeing if the piston is toast.

 

[Backstage]

Surprised no one jumped and pointed this out. You’re spraying in carb cleaner to help it start? You use that stuff to test for leaks because it prevents combustion.

 

[Okie]

So it's running good with 80-90 psi compression that you previously indicated?
Do you know if your gauge reads correctly on a chainsaw?

I seen a 170 that a guy brought me to check, he said he found it laying beside the road in a ditch. The saw would drop to the end of the pull rope with it's own weight. felt compression was really weak. I told him it's probably not going to run. Saw with compression that weak.
I squirted some prime into the carb throat and it briefly started on 2nd pull. Added fuel and it started and ran great and cut great.
Seen the guy about year later and he said it's a good saw in the firewood lot for trimming.

Sure wished to this day I had checked the compression on that little saw.

 

[MOOSETRAX]

Can’t remember the setting but 130 psi is low. I’d suggest taking the muffler off and seeing if the piston is toast.

hmm interesting Some say 110-150 psi is normal for the chain saw. Still thinking should i invest in a pistion & ring kit.

 

[Vintage Engine Repairs]

hmm interesting Some say 110-150 psi is normal for the chain saw. Still thinking should i invest in a pistion & ring kit.

That is a huge span. That covers everything from running perfectly fine to not even starting.

 

[Okie]

AND he indicates his 170 is now running fine at 80-90psi AS INDICATED ON HIS COMPRESSION GAUGE.

That is why I previously asked if he knew for sure that his compression gauge indicated correctly when testing a chainsaw. I seen several compression testers that would not read correct, usually a low readings. Even seen guys install new pistons and cylinder and their gauge read even lower afterwards and the saw still not run due to other problems such as bad carb/weak ignition, vac/pressure crankcase leak, bad spark plug.

 

[a. palmer jr.]

Some of the older 2 stroke engines will run on a lower compression, the ones with reed valves. I believe the newer engines all are piston ported and require around 150 to run right. The 170 is a piston ported engine..

 

[stihltech]

And I this is why we don't use a compression guage on two stroke saws. The starter handle test and visual inspection is what you need.

 

[Okie]

And I this is why we don't use a compression guage on two stroke saws. The starter handle test and visual inspection is what you need.

Read my post #29

That 170 would drop by it's own weight doing the rope/handle test.
Could not believe how easily it started and had good power in the cut.

The reason I did not check the compression it was not my saw and when something is working good FOR OTHER PEOPLE I leave it as is. (let a sleeping dog lay)

The guy actually brought me 2 170's at same time the other one was normal on the rope drop test.
The 3rd a guy had installed new piston and jug and still no run. (he said they tested the compression as still weak on his automotive gauge)
It had a bad carb.

 

[stihltech]

This is why STIHL has diagnostic charts. No compression reading on it.