MS171 tune changes daily

[tricky74]

Yes it does appear to have a limiter.
If I run it richer it four strokes.
Running it on 98 RON fuel at 50:1
The revs are a lot higher since I opened up the muffler.
Took me ages to find the air leak at the white ring between motor and carb.
Pushed it pretty hard yesterday and it seems pretty good.

 

[John_Mc]

Yes it does appear to have a limiter.
If I run it richer it four strokes.
Running it on 98 RON fuel at 50:1
The revs are a lot higher since I opened up the muffler.
Took me ages to find the air leak at the white ring between motor and carb.
Pushed it pretty hard yesterday and it seems pretty good.

Four strokes while in the cut? if so, that is too rich. Ideally, it should four stroke a full throttle out of the cut, then "clean up" under load.

Running significantly higher than the recommended octane does nothing other than cost you money, unless you have also modified the saw for higher compression (A muffler mod does not change the required octane.) It can make sense to buy a couple points higher octane as a safety buffer, since the octane rating of fuel can drop over time as various components of the fuel evaporate off while it is stored. For example, if the saw requires a minimum of 89 octane, it can make sense to buy premium (91 or 93 octane, depending in what is available in your area). Buying 100 octane racing fuel is generally a waste of money for a saw with stock compression.

 

[ericm979]

Also if you're pumping from a blender pump (one hose for multiple grades), the first gallon or so is whatever the previous customer pumped. I fill the 5 gallon fuel container for the saws with 91 figuring that it will average out to at least 89.

 

[yomax4]

Also if you're pumping from a blender pump (one hose for multiple grades), the first gallon or so is whatever the previous customer pumped. I fill the 5 gallon fuel container for the saws with 91 figuring that it will average out to at least 89.

Never dawned on me. now I'm kinda pissed. Sometimes I only buy 2 gallons of Non Ethanol and am probably getting E10 from the last guy that pumped. Won't happen again.

 

[tricky74]

Most of the fuel near me is either E10 or 98 the E10 is 94 RON not MON that USA states it in.

Yes I richened it up and it runs like **** and while in a cut I leaned it up until it cleaned up.
It is probably still too rich. It was either four stroking or on limiter pretty much.
Maybe I should lower the depth gauge another 5 thou and retune it again.

 

[John_Mc]

Also if you're pumping from a blender pump (one hose for multiple grades), the first gallon or so is whatever the previous customer pumped. I fill the 5 gallon fuel container for the saws with 91 figuring that it will average out to at least 89.

I buy my non-ethanol (E0) fuel from a station that sells 91 Octane E0 fuel from the same blended pump as their 87 and 89 octane 10% ethanol fuels. When filling cans for my small engines, I use the 91 octane E0 and pump the first couple of gallons into my car.

 

[ericm979]

Maybe I should lower the depth gauge another 5 thou and retune it again.

Depth gauge is different from tuning. I'd leave the gauges at a reasonable level. This is a small saw which will be cutting small stuff. deep gauges gets grabby on small stuff.
(If the teeth have been filed back a ways you might want to check with a progressive depth gauge checker. And make sure the gauge teeth are rounded on the top, not filed flat.)

If it's not cutting well enough with the normal depth gauge setting then the teeth need to be sharper.

 

[yomax4]

I buy my non-ethanol (E0) fuel from a station that sells 91 Octane E0 fuel from the same blended pump as their 87 and 89 octane 10% ethanol fuels. When filling cans for my small engines, I use the 91 octane E0 and pump the first couple of gallons into my car.

Good program. I'll be doing the same !

 

[tricky74]

Depth gauge is different from tuning correct but as it now revs so freely it was on limiter most of the time in a cut.
If I richen it up any it runs like a dog.
This is no longer what we would call a stock saw.

 

[yomax4]

I'll have to look up the rev limiter feature. I wonder what the rpm's are when the limiter kicks in. No limiters on any of my saws as far as I have noticed. All have muff mods and re-tuned. When I did the muffler mods all that was needed was about a 1/8 turn counterclockwise on my high screw and then adjust idle. Yours seems haunted.