Chainsaw query

[Sigidi]

So all those wiser ones out there....

I have a 372 which compliments my milling, the other day I was trying to dock some rounds to length and found she had no top end at all, reved well on maybe a quater of throttle, but couldn't move the chain on full throttle (and this wasn't while cutting , this was no load)

I thought my fuel was a bit old, so I turfed it and mixed a new batch, still same thing, anyway perservered and got done what I had to. Came home took the carby apart and cleaned it up thinking maybe some remnants from fuel still causing issues. Still no solution.

My fencing mate says to me its the mixture at top end, get out the little jewellers screwdriver and play with the 'H' screw when she's at operating temperature....

Well it fixed the problem, she revs out fine at full throttle now - so after all that, my question How does the saw become 'untuned' or how does the 'H' screw move from it's position? I was using the saw fine and then she didn't want to play anymore. What circumstances cause this?

TIA to everyone else out there.

[bobsreturn2003]

not sure ,sometimes a tiny piece of gunk gets stuck i guess and winding in and out seems to fix it . also mix and different oils make a difference .try and buy a saw you can access the screws ,and you shouldnt have to pull carby . good cutting bob

[Calm]

A lot of this can be caused by a dirty air filter as the dust collects in the filter - less air same fuel - too rich. Does the filter need cleaning often. The filter is not an oil or fuel soaked filter is it?

The initial setting for most saws is screw them fully in then out 1 1/2 to 2 turns out. This gives you a starting point adjust the idle speed and low jet then hold the saw on full throttle with the engine running adjust the High screw until the saw uns at best revs then turn it out almost another 1/4 turn. This gives a bit extra fuel for the load. If the low jet is too lean the saw tends to hesitate when you rev it up.

Hope that helps.

[Outbackrr]

Adding to the causes above: The carb diaphragms get weaker with age; losing a bit of compression over time also affects settings; and the springs that 'secure' the idle screws will also weaken over time and allow settings to change.