Author Topic: 357XP out of tune?  (Read 829 times)

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Offline John Mc

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357XP out of tune?
« on: July 22, 2012, 10:07:01 pm »
I fired up my 357XP today, after 2 or 3 weeks of sitting idle.  It started normally ran OK at idle (maybe a bit rougher than I remembered it?).  I had just put fresh fuel mix in it, which ran just fine in my Jonsered 2152.

When I tried to cut with it, it seemed slow... not cutting with it's usual speed (chain had just been sharpened).  After 4 or 5 cuts, I shut it down and went back to my 2152.

When I got back home, I put a tach on it.  It was maxing out between 11,000 and 11,500 RPM (no load). Air filter looks fine.  I adjusted the high speed mix by ear (which I'm still not the greatest at, but getting better), then checked with my tach. It was right at about 14,300 RPM.

What I can't figure out is what could have changed to throw it off that far in a couple of weeks.  It was running normally last time I used it.  I'm concerned that if whatever happened somehow undoes itself, I'll be running very lean.

Should I be concerned? Any ideas what to check?

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Offline man of stihl

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Re: 357XP out of tune?
« Reply #1 on: July 23, 2012, 04:52:12 pm »
That doesn't sound odd to me. I carry my little screw driver with me every time i get a saw out. Air temp, humidity, and different fuel mix effects the tune.
Ron

Offline Cut4fun .

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Re: 357XP out of tune?
« Reply #2 on: July 23, 2012, 05:06:48 pm »
Guess with all this new autotune saws we will never have to worry about this stuff in the future.   ;D

We will just have to worry about chasing a air leak we dont know we have because the autotune will adjust for it and run erratic.  ::)
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Offline John Mc

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Re: 357XP out of tune?
« Reply #3 on: July 24, 2012, 11:32:46 am »
That doesn't sound odd to me. I carry my little screw driver with me every time i get a saw out. Air temp, humidity, and different fuel mix effects the tune.

I know at least a little bit about how temp, humidity, and mixture affects an engine from my days as a flight instructor... I had to be able to explain some of the effects to my students.  What surprised me here was not that it changed, it's that it changed by several thousand RPM.  A few hundred RPMs I could understand.   

Temps were within 10˚F when I last ran it and this time around.  Humidity was probably not hugely different (just judging by my comfort factor. I did not actually check humidity levels.)  I was cutting in the same area, so altitude change was not an issue.  THe fresh fuel was premium ethanol-free, (as was the old fuel).  Even if the old fuel was E10, I would expect an effect similar to richening the mix when going from E10 to E0 gas.  I've just never had to adjust things to correct a 3000 RPM change before

Offline Cut4fun .

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Re: 357XP out of tune?
« Reply #4 on: July 24, 2012, 01:54:30 pm »
John I did have a difference of over that not to long ago in the heat on a 272. I traded the saw off running 32:1 100% synthetic and 93 octane. It came back to me with hardly any power in the cut. He was using that stihl orange bottle dino oil 50:1 and fuel octane ( I dont remember).
I started it and you could here the fat 4 stroking sound and test cut no r's or clean up in cut. Checked with tach 9k. When that saw left a few weeks prior it was 13k.  Seemed to take about a half turn leaner  H clockwise or more to bring her back around to right r's and in the cut power with his mix.

My 357 used to be erratic too. What I used to check 199 carb acting up, plastic clamp intake boot, tank vent, worn impulse line, fuel line. 
Friend has 357 now local that has erratic carb symptoms too  even at idle.
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Offline 660magnum

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Re: 357XP out of tune?
« Reply #5 on: July 24, 2012, 02:45:27 pm »
Every time I use my 357, I have to go through the carb needles again. And then it performs very well.
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Offline John Mc

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Re: 357XP out of tune?
« Reply #6 on: July 24, 2012, 03:32:19 pm »
I've had this 357 for 4 or 5 years. This is the first time I've seen such a dramatic shift.  I have had the plastic clamp replaced.  I thought the carb troubles were supposed to affect it at idle, not WOT.  At any rate, it's running OK now.  I'll check fuel and impulse lines to be sure... but wouldn't a problem there be more likely to make it run lean, rather than rich?

Thanks for the pointers...

John

Offline Cut4fun .

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Re: 357XP out of tune?
« Reply #7 on: July 24, 2012, 03:35:33 pm »
Yep.  But still make it a bear to tune with a pin hole or **** line.
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