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Too much transfer duration

David Young

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How do I know if I have too much transfer duration.

Runs like crazy. If I bury bar noodle and really push it will stall out but it sounds like the saw is flooding out. Also fuel consumption is rather progressive. How do I recover more blowdown? Or is it tfb?
 

Wigglesworth

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How do I know if I have too much transfer duration.

Runs like crazy. If I bury bar noodle and really push it will stall out but it sounds like the saw is flooding out. Also fuel consumption is rather progressive. How do I recover more blowdown? Or is it tfb?

Gonna need a bit more info. What saw? What timing numbers? Tuned correctly?

Transfers are funny sometimes, at least to me. Sometimes the difference between running, and running like a bastard is just a misshapen corner, or a couple degrees. Too little duration and they act lean, too much duration and they can act lean as well.

It takes fuel in the chamber at exactly the right time to make maximum power...
 

David Young

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Gonna need a bit more info. What saw? What timing numbers? Tuned correctly?

Transfers are funny sometimes, at least to me. Sometimes the difference between running, and running like a bastard is just a misshapen corner, or a couple degrees. Too little duration and they act lean, too much duration and they can act lean as well.

It takes fuel in the chamber at exactly the right time to make maximum power...


Ms310
126 duration
ex. 160


runs like a scalded dog until I really push on it.
 

Al Smith

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I assume you are talking about a stock saw .Firstly if I recall correctly a 310 is a clamshell designed like a 290 .Also I believe the carb has fixed limiters on it .

What you likely have has not one thing to do with the duration of the transfer cycle but more to do with fuel delivery .If said saw cannot deliver the fuel in a heavy cut it will falter .As designed small saw or no it should be able to hang tough with the bar buried .

Now if you've got into it and fiddled with the port timing all bets are off on what I said .
 

David Young

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Consider it fiddled.

I assume you are talking about a stock saw .Firstly if I recall correctly a 310 is a clamshell designed like a 290 .Also I believe the carb has fixed limiters on it .

What you likely have has not one thing to do with the duration of the transfer cycle but more to do with fuel delivery .If said saw cannot deliver the fuel in a heavy cut it will falter .As designed small saw or no it should be able to hang tough with the bar buried .

Now if you've got into it and fiddled with the port timing all bets are off on what I said .



Yeah I messed with it a little. I had the timing advance and ended up backing it off a bit.
http://m.youtube.com/watch?v=ZYB-4UCoR4s.
 

Al Smith

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Contrary to popular belief it doesn't always help to jack the ignition timing .A standard Stihl is around 27 degrees advance already .Now I've had success on McCullochs' which are 26 advance but they have a slightly lower compression ratio than most Stihls .

I was talking about altering the port timing like raising the exhaust port .
 

naked arborist

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Yeah I messed with it a little. I had the timing advance and ended up backing it off a bit.
http://m.youtube.com/watch?v=ZYB-4UCoR4s.

Try this:
Choke the muffler back up just a bit. Finer mesh in the screen should do it or add one back on the larger exhaust port. The 029 has the same problem at 125. You need to put the back pressure on it with the bigger bar buried. Seems like most of those carbs loose the vacuum signal when pushed to their limits. Zama just can't hang with a good old fashion Walboro that low in the R's. Let me know if that works out for you.
 

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