Tuning

[shiggins]

hey

I'm after some advise on tuning my dolmar ps410.

I just put a new fuel hose in and the carby now needs adjusting. Any advise? I followed some instructions that are in the oleo mac thread but I'm not sure if I can do the same with this saw.

Cheers.

[shiggins]

I've got it cutting well.

I backed the high and low out 1 and a half turns but needed the low to be only one turn out for it to run. The filter was clean as well as the carby screws.

I then followed the instructions in the oleo mac thread from @joe_indi .

"clean Lean setting of H and L screws. Turn them out 2 turns from the stop (that should raise some eyebrows)
start her up.
If it starts up blip the throttle without holding high revs for too long. One the engine is warmed up, tighten the idle screw so that the engine idles without your hand on the throttle.
With screwdriver in place on H screw, take it to full revs and turn in the screw till the  four stroking just stops, leave the throttle and back out the H screw by a little less than a quarter turn.
Turn in the idle screw to its stop to get a fast idle. Screw in L screw till idle increases. Back off the screw a bit. Set idle screw to a bit faster idle."

now with the 4 stroking i screwed the h screw in until it revved high and then tried the stall. I then backed it back so it would;t blubber (stall) so it was revving high and then backed it off a tad more, about a quarter turn. is this going to be ok? any advise will be appreciated, especially if its going to help the saw. is it worse having it revving to high or to low? or are both bad?

[John Mc]

I'm no mixture setting expert, but something to consider if you are not sure, or while you are waiting for advice from someone more knowledgeable than I am:

If you are going to be off on the high mixture setting, it's generally better to be off a bit on the rich side (screw backed out) than to be too lean. A bit too rich might foul a plug, but at least it won't burn up your saw like being too lean can.

I'm not sure what you mean by "stall", but the saw should blubber a bit when run at wide open throttle under no load (don't do this for extended periods), and then "clean up" when cutting. If it keeps blubbering in the cut, you are too rich. If it doesn't blubber when out of the cut, you're on the lean side.

It's also best to set the saw when warmed up and running the fuel you will be using. For example, don't set the mixture when running non-ethanol gas, then switch to ethanol gas (E10) when working - you may be OK, but the mixture will change slightly with the change in fuels.  Without changing the mixture, as saw will run a bit leaner on E10 gas than it will on non-ethanol gas.

Remember to listen to your saw when working. It will talk to you. If the tone changes, or the power seems off, you might be developing a problem.

[shiggins]

I'm no mixture setting expert, but something to consider if you are not sure, or while you are waiting for advice from someone more knowledgeable than I am:

If you are going to be off on the high mixture setting, it's generally better to be off a bit on the rich side (screw backed out) than to be too lean. A bit too rich might foul a plug, but at least it won't burn up your saw like being too lean can.

I'm not sure what you mean by "stall", but the saw should blubber a bit when run at wide open throttle under no load (don't do this for extended periods), and then "clean up" when cutting. If it keeps blubbering in the cut, you are too rich. If it doesn't blubber when out of the cut, you're on the lean side.

It's also best to set the saw when warmed up and running the fuel you will be using. For example, don't set the mixture when running non-ethanol gas, then switch to ethanol gas (E10) when working - you may be OK, but the mixture will change slightly with the change in fuels.  Without changing the mixture, as saw will run a bit leaner on E10 gas than it will on non-ethanol gas.

Remember to listen to your saw when working. It will talk to you. If the tone changes, or the power seems off, you might be developing a problem.

Thanks for the advise mate. Defiantly understand the saw talking to me. It realy does let u know when something's wrong. By stall I mean it eat to much gas when u have the throttle open and it stalls. The engine stops. Yeh?

[John Mc]

Understood.  If the saw it stalling on you as you describe, that's way too rich.  You jus want a little bit of blubber -- the tone changes a bit.

Check out the "saw tuning" link on Madsen's Saw Maintenance page  They've got a good audio file of a saw running rich, then lean so you can hear what folks are talking about with the "blubber". (I couldn't hear it very well until I switch to a computer with better speakers.)

[shiggins]

thanks mate