I have been reading about changing ignition timing on saws on this site yet I haven't a clue on how it is done on a chainsaw. Can somone please explain how it is done? does it involve relocating the keyway on the flywheel or does changing location of the coil do the trick. These are the only two things that I can think of that would change timing. I would really like to know.
Ignition timing for chainsaw
- Thread starter rutterb
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On modern saws, ..yes.
Some have made a "split key" on the flywheeel and advanced the timing a half key width.
Others have removed the key and fastened the flywheel in a new position without a key.
The magic numbers are somewhere between 28 - 32 degrees total advance.
Some modern ignitions have an advance curve built into them
The top dead center position has to be found with a piston stop as half the distance between the piston stop positions in both directions.
The timing position has to be found with a timing light and then the difference is measured with a degree wheel
Advancing timing too far may cause the chainsaw to over heat.
To advance the timing beyound 25 degree BTDC shows only slight gains and to go beyond 32 degrees often creates trouble.
If the timing is advanced very far at all at idle, the chainsaw will kick like a mule to try to start it.
Others have removed the key and fastened the flywheel in a new position without a key.
The magic numbers are somewhere between 28 - 32 degrees total advance.
Some modern ignitions have an advance curve built into them
The top dead center position has to be found with a piston stop as half the distance between the piston stop positions in both directions.
The timing position has to be found with a timing light and then the difference is measured with a degree wheel
Advancing timing too far may cause the chainsaw to over heat.
To advance the timing beyound 25 degree BTDC shows only slight gains and to go beyond 32 degrees often creates trouble.
If the timing is advanced very far at all at idle, the chainsaw will kick like a mule to try to start it.
If you time the saw without using the key, make sure you tighten the flywheel good and mark it. It'll save you a lot of grief if you have to remove the flywheel for anything.
A lot of the saws I've messed with are timed at about 30 degrees before TDC.
You can use an automotive timing light to time them, at least in some instances. I've taken off the flywheel cover, removed the spark plug, and used an electric drill to turn it over. I had to use a lawnmower battery to power the timing light. If you have a points system you can just use an ohm meter to set the timing. Most saws don't need this, I was experimenting on an Echo that I couldn't find ignition parts for.
A lot of the saws I've messed with are timed at about 30 degrees before TDC.
You can use an automotive timing light to time them, at least in some instances. I've taken off the flywheel cover, removed the spark plug, and used an electric drill to turn it over. I had to use a lawnmower battery to power the timing light. If you have a points system you can just use an ohm meter to set the timing. Most saws don't need this, I was experimenting on an Echo that I couldn't find ignition parts for.
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Changing the timing gets into some deep thought and disappointments sometimes because some coils have a built in advance, some coils have a retard and then back to the original position etc. Some coils do not advance or retard.
You never know what you have until you get into it.
It is best not to fiddle with timing or switching coils unless you are prepared to ferret out what is going on and can always return the chainsaw into its original configeration.
You never know what you have until you get into it.
It is best not to fiddle with timing or switching coils unless you are prepared to ferret out what is going on and can always return the chainsaw into its original configeration.
Ian rogerson
New Member
Hey guys i have just built a farmertec 070 saw and am not sure about ignition timing, looks to be a electronic module and coll set up, there is adjustment slots on base plate but net sure how to set it up
Metallichg
ArboristSite Operative
I did it on some of my 090 stihl saws. Had to buy a static timeing light and needed to mount a dial indicator in the spark plug hole. Was not easy and setting the points prior to rotating the stator was a pain too, but when you get the timeing right on, it really comes to life. I only know 090 saws, so can't comment on anything else.
Ian rogerson
New Member
I used the dial gauge to find TDC then marked fan wheel with a dot of white paint then marked it again at 12th (about 4 degrees) BTDC on dial guage. Connected timing light and started saw, mark showed about 1 inch before 4 degree mark?. Tried adjusting base plate but didn't make much difference. Timing mark did advance a little when motor reved. Saw seems to start and run good. Any ideas on this? guys.
Metallichg
ArboristSite Operative
I never used a timeing light on a static timed 090. I would get a static timeing light (not a test light or continuity testor). you have to take into account the high voltage that goes across the points as the arc needs to be accounted for as it will alter the timeing. I think the manual calls for 10mm btc for the points to open.
All of the old McCulloch saws were 26 degrees before top dead center. Kart engines had a flywheel with an additional 5 degrees advance.
If you alter it to near zero advance it will run in either direction, but poorly.
Mark
If you alter it to near zero advance it will run in either direction, but poorly.
Mark
I think you're good to go!
What is the diameter of the flywheel?, or model & make of the saw? 1" is anout 19 degrees on a 6" FW.
The charge capacitor will actually advance the timing a bit on an electronic type ignition when the rpm increases, due to the faster charge/discharge voltage rate.
Also in the post above about "advanced timing too far causes overheating" is wrong, it's retarded timing that will cause a gas engine to overheat...
Yes, phi times the diameter divided by 360 gives you inches per degree.
I used to plot out timing tapes using 'puter aided software.
Handy when you want to set timing on a 427" Chebby to get 36 degrees (initial plus centrifugal) all in at 2700 rpm.
I used to plot out timing tapes using 'puter aided software.
Handy when you want to set timing on a 427" Chebby to get 36 degrees (initial plus centrifugal) all in at 2700 rpm.
Ian rogerson
New Member
Re farmertic 070 timing. I have checked timing again with a digital timing light. TDC mark showed at crank angle of 33 degrees. Was advised for a 105cc to measure 3.1 mm BTDC with dial guage and mark case. When checked with timing light mark was in same place as before around 33 derees crank angle. Saw starts and runs good. Will cut timber and see how it performs. Thanks guys.
