Part Five: Ignition Timing

[mdavlee]

This saw is not ported, maybe on one of my ported ones (they have about .020).

Have you tested .020/.025 against .035???

I did years ago. Can't really remember but I go farther than .020" on all of them still.

 

[Stump Shot]

In and of itself a timing advance does not as much good unless a expected rise in RPM is expected. So I believe it's part of the whole package and helps everything work together kind of a thing. As the faster an engine goes the more advance is required.

As a side note, I am working on a fast, simple, easy and accurate way to measure actual timing in a modern power saw(modulated coil). If proven correct and true, I will share it with all you guys.

not yet, if someone knows where to get one please et me know.

Figured that I better make good on my promise at the beginning of the thread, to come up with an easy way to check the timing on a power saw. I believe that this is as best that I could make it.

First take the top off and install a dial indicator in the spark plug hole. Find TDC and mark flywheel. I used a pointer, another mark lined up is just as good.



Fire up the saw and find out where you are at. This 266 came in just under 26 degrees of advance. This only took a matter of minutes to accomplish as I did not have to tear the saw down more to use a degree wheel. Not that there is anything wrong with that, just takes a little more time is all.


This is a Bosch digital advance timing light - FIX 7529, purchased at O'REILLY'S Auto parts. Has 2 and 4 cycle capability. Has a tachometer feature. Says it is good to 9,999 RPM. When I exceeded this it just started over again at 1, or 10,001. The timing light never did go out on this saw.

@tree monkey this may be the light you are looking for, I don't have anything as fast as your saw's to test it on though. Lol

I hope that this helps some folks with checking the timing of a power saw. SS

 

[Stump Shot]

Thought I would mention the new Bosch digital timing light was $89.99 at O'Reilly's. Which I did not think was too bad compared to the prices I saw online of $120.00 and up.

 

[Dub11]

Figured that I better make good on my promise at the beginning of the thread, to come up with an easy way to check the timing on a power saw. I believe that this is as best that I could make it.

First take the top off and install a dial indicator in the spark plug hole. Find TDC and mark flywheel. I used a pointer, another mark lined up is just as good.

View attachment 72943

Fire up the saw and find out where you are at. This 266 came in just under 26 degrees of advance. This only took a matter of minutes to accomplish as I did not have to tear the saw down more to use a degree wheel. Not that there is anything wrong with that, just takes a little more time is all.

View attachment 72944
This is a Bosch digital advance timing light - FIX 7529, purchased at O'REILLY'S Auto parts. Has 2 and 4 cycle capability. Has a tachometer feature. Says it is good to 9,999 RPM. When I exceeded this it just started over again at 1, or 10,001. The timing light never did go out on this saw.

@tree monkey this may be the light you are looking for, I don't have anything as fast as your saw's to test it on though. Lol

I hope that this helps some folks with checking the timing of a power saw. SS

Were did you get that dial indicator holder at?

 

[Stump Shot]

Were did you get that dial indicator holder at?

MAC Tools, back in time so far I can't remember. Used units can be found on Flea Bay, other manufacturers as well.

 

[Dub11]

MAC Tools, back in time so far I can't remember. Used units can be found on Flea Bay, other manufacturers as well.

Whats it official name?

 

[Sty57]

Whats it official name?

Do a search for "top dead center dial indicator"

 

[srcarr52]

You can always use a piston stop and mark the case or flywheel in both directions... then half way between them is TDC.

 

[Stump Shot]

You can always use a piston stop and mark the case or flywheel in both directions... then half way between them is TDC.

Excellent! Another great way and easy to do. If your young and talented you could probably use a straw from McDonald's and get the feel for TDC. My main idea though was to not have to tear the saw half apart just to check it. I'm sure people will be able to add their own twist on this to suite their needs.

Also for the record, I really did/do like the new timing light, it far exceeded my expectations. Worth every penny for me, and I'm not accustomed to saying this about new things.

I did look on Flea Bay they do have new affordable units, a lot for dirt bikes. Just make sure you have the right thread size and be careful to not slap the piston on it so as to bend the indicator arm, they are OK, I have a set up like that as well. For just finding TDC it is all you need, the angled ones to line up with the stroke are for a more accurate measurement when setting point style ignitions. Not really done much any more, except by a few relics like me.

 

[Sty57]

Excellent! Another great way and easy to do. If your young and talented you could probably use a straw from McDonald's and get the feel for TDC. My main idea though was to not have to tear the saw half apart just to check it. I'm sure people will be able to add their own twist on this to suite their needs.

Also for the record, I really did/do like the new timing light, it far exceeded my expectations. Worth every penny for me, and I'm not accustomed to saying this about new things.

I did look on Flea Bay they do have new affordable units, a lot for dirt bikes. Just make sure you have the right thread size and be careful to not slap the piston on it so as to bend the indicator arm, they are OK, I have a set up like that as well. For just finding TDC it is all you need, the angled ones to line up with the stroke are for a more accurate measurement when setting point style ignitions. Not really done much any more, except by a few relics like me.

I had one at one time for my sleds.........But it grew legs.
This one had a little wheel on the end of the indicator arm so it would roll on the top of the piston. I believe I got that one through Ski-doo or maybe it was FAST I can't remember anymore.

 

[Stump Shot]

I had one at one time for my sleds.........But it grew legs.
This one had a little wheel on the end of the indicator arm so it would roll on the top of the piston. I believe I got that one through Ski-doo or maybe it was FAST I can't remember anymore.

Have an old Merc-O-Tronic made mostly for snowmobiles. Here I am using it on and old Stihl with points.

 

[Chainsaw Jim]

I'm sure people will be able to add their own twist on this to suite their needs.

All you need to do is look at the piston through the spark plug hole or exhaust port to watch it peak out. Center up the dwell if it's measurable.

 

[Stump Shot]

All you need to do is look at the piston through the spark plug hole or exhaust port to watch it peak out. Center up the dwell if it's measurable.

Awesome, one more way to find TDC. This further shows just how easy it is to find TDC without the aid of a degree wheel. None of which is new or revolutionary, and if done right is not corner cutting, but rather time saving.

 

[Dub11]

Do a search for "top dead center dial indicator"

Thanks

 

[srcarr52]

Awesome, one more way to find TDC. This further shows just how easy it is to find TDC without the aid of a degree wheel. None of which is new or revolutionary, and if done right is not corner cutting, but rather time saving.

Degree wheels and piston stops are much more accurate than a dial indicator due to the dwell at TDC.

 

[Stump Shot]

Degree wheels and piston stops are much more accurate than a dial indicator due to the dwell at TDC.

Well I did fail to mention that the dwell does need to be worked out, but is reasonable and a standard procedure for lots of other especially older motors. So I decided to see what I could do with piston stops, it turned out too far and difficult on this application to be practical. So I scratched that idea for now, and tried out a gauge at the same angle as the spark plug. I came up with the same answer as the angled one. Also tried using just a big Allen wrench down the spark plug hole, and was able to work it out that way as well. It does take a little bit to get the nack, once you have it though, it is pretty easy and accurate.

 

[MattG]

Just found this - I'm not sure whether you guys have covered this stuff yet.

Is the guy saying that one coil adjusts the advance as revs rise, but the other one always keeps the same advance angle throughout the range?

 

[MustangMike]

Yes, some coils advance (really they retard for idle) and others are fixed. Most modern ones advance, I'm surprised the 360 coil did not.

 

[MattG]

Yes, some coils advance (really they retard for idle) and others are fixed. Most modern ones advance, I'm surprised the 360 coil did not.

Indeed yeah...(thought I'd heard him right).

Regards the modern coils, I suppose that that is a plus point of the limited coils, is despite having the limiter circuitry, some may be well have a better dynamic performance - i.e. more optimal for idle, high revs/low load, medium revs/high load (?)

 

[paragonbuilder]

Indeed yeah...(thought I'd heard him right).

Regards the modern coils, I suppose that that is a plus point of the limited coils, is despite having the limiter circuitry, some may be well have a better dynamic performance - i.e. more optimal for idle, high revs/low load, medium revs/high load (?)

Yes I know on the dolmars 6400-7900 series, there are a few coils. All are limited, but the high limited one isn't as strong in the cut. Different advance curve.


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