Stihl saws kickback on starting

[scruffy808]

Hi there, New to this forum but might have some info to help here.
It seems many have problems with Stihl saws kicking back on starting, hard to start or causing injury or at least shyness on new pull!!
Appears for some models like MS660 there are different later part number coils available that have ignition retard and/or advance built into the design (?).
Can relate to aftermarket ignition coils certainly affecting ignition timing, also the air gap between the coil armature and flywheel magnets is most important.
Too small a gap appears to advance the ignition timing although not by much.
One solution using the ignition coil that promotes kickback is to retard the timing.
Method: Its nothing fancy - a trial and error method to see what works for your saw in its condition, state of tune and with your starting technique.
Step 1 - Procure a timing light preferably an automotive strobe type using a 12V battery. Pull saw down to get at entire flywheel area.
Step 2 - Remove spark plug, fit up timing light to determine timing- use existing flywheel rim markings or make your own ink pen marks for a true TDC .
Step 3- Turn engine over slowly in normal rotation direction- use a drill or power screwdriver but not too fast to simulate pull starting speed. (Be mindful flywheel retaining nut may unscrew dont use impact driver.) Using strobe light , mark on casing where the ignition point is - relative to TDC mark.
Most likely this will be well before TDC hence the kickback tendency. Some of these problem saws are 20 degrees BTDC with this test!!
Step 4- Pull flywheel off, discard woodruff key. Retard flywheel position on crank, a small amount reassemble recheck timing.
Only a few degrees may be needed to stop kickback - sorry did say trial and error!! Try saw now on starting kickback tendency -no good go again.
Just prempting those against discarding the key- The woodruff key does NOT hold the flywheel in place ONLY aids in getting a reproduceable factory timing easily.
Tightening the flywheel retaining nut properly AND the flywheel will stay where its place forever. The tapers on the parts are self locking. Yes would be a better press fit joint without the keyway in the flywheel buts thats what we have to work with.
Welcome comments - try this out it will work just a lot of D and A required plus its hard to get timing "correct" again if flywheel is pulled.
Maybe someone reading this can tell us how to do that also how much retard works on which models?? Thanks for reading, Scruffy808

 

[angelo c]

Post an update on saw performance after said mod please...many here do the same with a BGD(base gasket delete) and a muffler massage and get positive " affordable" gains...without serious lathe expenses

 

[angelo c]

Lots of us open up the "port" on the decomp button as well. Or swap to the 395xp blue button as it seems to have the largest opening

 

[leaf]

Hi there, New to this forum but might have some info to help here.
It seems many have problems with Stihl saws kicking back on starting, hard to start or causing injury or at least shyness on new pull!!
Appears for some models like MS660 there are different later part number coils available that have ignition retard and/or advance built into the design (?).
Can relate to aftermarket ignition coils certainly affecting ignition timing, also the air gap between the coil armature and flywheel magnets is most important.
Too small a gap appears to advance the ignition timing although not by much.
One solution using the ignition coil that promotes kickback is to retard the timing.
Method: Its nothing fancy - a trial and error method to see what works for your saw in its condition, state of tune and with your starting technique.
Step 1 - Procure a timing light preferably an automotive strobe type using a 12V battery. Pull saw down to get at entire flywheel area.
Step 2 - Remove spark plug, fit up timing light to determine timing- use existing flywheel rim markings or make your own ink pen marks for a true TDC .
Step 3- Turn engine over slowly in normal rotation direction- use a drill or power screwdriver but not too fast to simulate pull starting speed. (Be mindful flywheel retaining nut may unscrew dont use impact driver.) Using strobe light , mark on casing where the ignition point is - relative to TDC mark.
Most likely this will be well before TDC hence the kickback tendency. Some of these problem saws are 20 degrees BTDC with this test!!
Step 4- Pull flywheel off, discard woodruff key. Retard flywheel position on crank, a small amount reassemble recheck timing.
Only a few degrees may be needed to stop kickback - sorry did say trial and error!! Try saw now on starting kickback tendency -no good go again.
Just prempting those against discarding the key- The woodruff key does NOT hold the flywheel in place ONLY aids in getting a reproduceable factory timing easily.
Tightening the flywheel retaining nut properly AND the flywheel will stay where its place forever. The tapers on the parts are self locking. Yes would be a better press fit joint without the keyway in the flywheel buts thats what we have to work with.
Welcome comments - try this out it will work just a lot of D and A required plus its hard to get timing "correct" again if flywheel is pulled.
Maybe someone reading this can tell us how to do that also how much retard works on which models?? Thanks for reading, Scruffy808

 

[leaf]

It would be great somehow to start a little "movement" that would force any company making and marketing any chainsaw to show / print the designed / factory "installed" / "intended" ignition timing profile in the published manuals regarding any saw. This may seem like a "nothingburger" to many of the people on this forum, BUT a) in fact it is now common to have timing electronics within saw ignition modules (the black lump from which the plug wire emerges) b) it is a bit of a pain to measure chainsaw ignition timing (start saw w/ cover/ take cover off / point timing light / make marks, play with degree wheel etc.) and somewhat imprecise c) often the electronics aren't fundamentally that "sturdy" -- (RC circuit / trigger, etc. style). I have a couple of saws and have seen a few, but one doesn't know from the beginning when some saw that has "problems" approaches whether it (like some Huskys) starts at relative ignition retard, or it is designed for some "push" at advanced -- and also is that way from the start (some Stihl) ... or even can usually be "helped" to get more "zap" in use (e.g. Husky top handles)

Anybody / Everybody can join in -- and when talking to any saw "reps" / customer "service" people, etc. etc. people at trade shows, just say "Stop being pigs.... and put the timing in the book." (If it really works... well, then they can publish port timing, too... hunh)

 

[scruffy808]

It would be great somehow to start a little "movement" that would force any company making and marketing any chainsaw to show / print the designed / factory "installed" / "intended" ignition timing profile in the published manuals regarding any saw. This may seem like a "nothingburger" to many of the people on this forum, BUT a) in fact it is now common to have timing electronics within saw ignition modules (the black lump from which the plug wire emerges) b) it is a bit of a pain to measure chainsaw ignition timing (start saw w/ cover/ take cover off / point timing light / make marks, play with degree wheel etc.) and somewhat imprecise c) often the electronics aren't fundamentally that "sturdy" -- (RC circuit / trigger, etc. style). I have a couple of saws and have seen a few, but one doesn't know from the beginning when some saw that has "problems" approaches whether it (like some Huskys) starts at relative ignition retard, or it is designed for some "push" at advanced -- and also is that way from the start (some Stihl) ... or even can usually be "helped" to get more "zap" in use (e.g. Husky top handles)

Anybody / Everybody can join in -- and when talking to any saw "reps" / customer "service" people, etc. etc. people at trade shows, just say "Stop being pigs.... and put the timing in the book." (If it really works... well, then they can publish port timing, too... hunh)

Fully agree ignition timing seems to be a secret no chainsaw manufacturer I know off publishes. Guess they reckon its not something that can be adjusted so no need to know. Like someone to tell us how some of these ignition coils actually retard and advance timing, there must be an explanation out there some place.

 

[leaf]

Yuh, but Dr. Scruffy... a) as you correctly describe, it IS something that can be adjusted, easily "in gross" (all forward / back) and (with a bit more messing) "in detail" (by changing values of timing function / one module or another, b) AND it affects ... 1) ease/ difficulty of starting 2) so-called starting "kickback" 3) temperature during combustion 4) head temperature and exhaust temperature 5) "knocking" (combustion rate and pressure propagation), 6) "flywheeling" and other RPM change properties 7) power 8) exhaust gas and "emissions" qualities (from unburned hydrocarbons to NOX, etc.) and 9) the many things that those things affect (temperature changes lubricating oil performance... etc. etc.)

I do NOT claim to know, but I would guess that the way the modules work is pretty simple. Ignition coils are ignition coils, pulse makes pulse (low voltage in one set of (some) turns of wire around a core becomes induced high voltage in another coil of many turns when input current is quickly "broken") Timing is thus about "operating the switch" at some moment. Choices for "switch" are either darlington pair, or FET, or IGBT some other (very similar) semiconductor (transistor type). The switch is "switched" by some "trigger circuit" hopefully that has some noise immunity and some hysteresis AND is stable (at least as intended) across a range of circuit voltages. I'll guess that typical "timing" as timing is not more sophisticated than "charge on a capacitor." (A lot of the timing varying circuits would "detect RPM" by voltage -- magnet on coil voltages increase w/ speed. For example, I believe - but do not know - that Husqvarna starts w/ the retard at pull cord speed, and then moves to normal advance at idle and up -- and probably does that by sensing voltage as the magnet passes. Often, as you get going closer to really fast -- max RPM -- you want to stop advancing -- for heat and control and other reasons.)

In any event, it would be very reasonable for different people using a given saw to want different ignitions in it, depending upon whether they start the saw a lot, or start it once and need major power, or need to make sure they don't get it too hot...

AND, it would be great for the sake of fixing saws (rather than throwing them out ... which enough of the people in -- particularity the "landscaping for rich people" business -- seem to do... if a person could know what the intended timing / RPM was and use it helpfully in saw owning / managing...

 

[scruffy808]

Yuh, but Dr. Scruffy... a) as you correctly describe, it IS something that can be adjusted, easily "in gross" (all forward / back) and (with a bit more messing) "in detail" (by changing values of timing function / one module or another, b) AND it affects ... 1) ease/ difficulty of starting 2) so-called starting "kickback" 3) temperature during combustion 4) head temperature and exhaust temperature 5) "knocking" (combustion rate and pressure propagation), 6) "flywheeling" and other RPM change properties 7) power 8) exhaust gas and "emissions" qualities (from unburned hydrocarbons to NOX, etc.) and 9) the many things that those things affect (temperature changes lubricating oil performance... etc. etc.)

I do NOT claim to know, but I would guess that the way the modules work is pretty simple. Ignition coils are ignition coils, pulse makes pulse (low voltage in one set of (some) turns of wire around a core becomes induced high voltage in another coil of many turns when input current is quickly "broken") Timing is thus about "operating the switch" at some moment. Choices for "switch" are either darlington pair, or FET, or IGBT some other (very similar) semiconductor (transistor type). The switch is "switched" by some "trigger circuit" hopefully that has some noise immunity and some hysteresis AND is stable (at least as intended) across a range of circuit voltages. I'll guess that typical "timing" as timing is not more sophisticated than "charge on a capacitor." (A lot of the timing varying circuits would "detect RPM" by voltage -- magnet on coil voltages increase w/ speed. For example, I believe - but do not know - that Husqvarna starts w/ the retard at pull cord speed, and then moves to normal advance at idle and up -- and probably does that by sensing voltage as the magnet passes. Often, as you get going closer to really fast -- max RPM -- you want to stop advancing -- for heat and control and other reasons.)

In any event, it would be very reasonable for different people using a given saw to want different ignitions in it, depending upon whether they start the saw a lot, or start it once and need major power, or need to make sure they don't get it too hot...

AND, it would be great for the sake of fixing saws (rather than throwing them out ... which enough of the people in -- particularity the "landscaping for rich people" business -- seem to do... if a person could know what the intended timing / RPM was and use it helpfully in saw owning / managing...

Thanks Leaf your explanation how the ignition electronic controls alter timing is excellent, feel sure many readers (and me especially) will benefit from that. All my suggestions were just around the kick back problem- I know saw owners who have given up on a perfectly good large saws and bought a new saw just because of hard starting and kick back. Fully agree changing timing will affect power, temperatures, emissions etc but none of this matters if you cannot start thing safely!!
Thanks again perhaps we can close down on this kick back issue- like to hear from any others how much ignition retard was needed - even if an estimate- to help with starting kickback problems. Especially on older saws lacking all the electronic advance/retard features.

 

[Okie]

Speaking of timing on a chainsaw and electronics I had 4 of the Nova II reversible polarity chips that were designed for doing away with the points and condensers on chainsaws.
Each chip of the same design part number would cause the same chainsaw to have different timing and one of the chips required it be connected for opposite polarity input to the chip. After seeing this first hand I suspected the chips were most likely not made in the USA and my testing confirmed were of poor design quality. When I consulted the vendor about my findings they made a complete refund and indicated they were going to stop selling the Nove II chips because of complaints of failures.
I've used some of the old NLA atom chips with good results.
Point being if the electronics trigger circuits being installed by the manu, (transistors, etc, of not of good quality you are just rolling the dice.

I was going to check the ignition timing using the inductive 12vc timing light method you suggested with one of the 4 chips that the saw started easy and ran really good but the chip failed before I got to the test. I just went back to the old points/condenser for reliability.

Some of the older 4 cycle small engines (Tecumsehs and Gravelys for example) timing could be changed by rotating the points plate on the small Tecumsehs and if the timing got too much advanced and the engine would start and run the rod would go south. A hint that timing was too far advanced was hard kickback when trying to start and with some you could detect/hear the spark knock.

 

[scruffy808]

Great feedback Okie, I have a Stihl 031 with an Atom "brown" color electronic module conversion replacing the points. When original coil failed I fitted an aftermarket item, saw never ran good then- backfiring thru carby, flat sounding and little response to carby tuning needles. Suspecting retarded timing sure enough it was badly retarded firing well after TDC using automotive timing light. The earlier thread I wrote with moving flywheel to advance timing and discarding the woodruff key was the fix. BTW the Atom module has to be well over 35 years old, as you say no longer available wish they were they were good modules.

 

[Okie]

Great feedback Okie, I have a Stihl 031 with an Atom "brown" color electronic module conversion replacing the points. When original coil failed I fitted an aftermarket item, saw never ran good then- backfiring thru carby, flat sounding and little response to carby tuning needles. Suspecting retarded timing sure enough it was badly retarded firing well after TDC using automotive timing light. The earlier thread I wrote with moving flywheel to advance timing and discarding the woodruff key was the fix. BTW the Atom module has to be well over 35 years old, as you say no longer available wish they were they were good modules.

I've got a list filed on my computer of the different model number and color of the old NLA Atom chips. They were made to be equipment/motor specific by model and color code. You can still find this color and model number for eq use info on-line with little bit of searching.

I keep one or two Atom chips within easy reach in my chainsaw tools just to test a points type chainsaw as a bypass test of the points/condenser if I suspect that is the saws start/run issue W/o having to first pull a flywheel.
A guy gave me a old Homie sometime back not running and it had a old Atom installed. The ignition was Ok, had bad carb. After getting the saw carb running I installed new points/condenser and SAVED the cherished Atom chip as a future test tool.

 

[oldercut]

I've got a list filed on my computer of the different model number and color of the old NLA Atom chips. They were made to be equipment/motor specific by model and color code. You can still find this color and model number for eq use info on-line with little bit of searching.

I keep one or two Atom chips within easy reach in my chainsaw tools just to test a points type chainsaw as a bypass test of the points/condenser if I suspect that is the saws start/run issue W/o having to first pull a flywheel.
A guy gave me a old Homie sometime back not running and it had a old Atom installed. The ignition was Ok, had bad carb. After getting the saw carb running I installed new points/condenser and SAVED the cherished Atom chip as a future test tool.

Hi; my question is can any of these chips ( used to replace the points & cond ) be used with out changing the flywheel ? My saw is originally points/cond and I have seen somewhere that to change to electronic ign. requires a different flywheel
Also, thanks to Scruffy for the comments on changing the timing
and to Okie for comments on coils & timing.
My 031 is still not running as I suspect a bad coil. The primary & secondary resistances check out but I suspect a fault.
Thanks to all .

 

[Okie]

Just to let you know that I do not know the answer to your question about your STIHL 031.

I can tell you this much about my OLD Stihl saws that use points/condenser ignition plus some other old saws I have that are points/condenser. If I can get parts within reason to repair the ORIGINAL type points/condenser ignition systems I repair them as is instead of going to electronic. WHY, because i have some old 028's and other brands/makes of saws that are 40 to 50 years old and still have the OEM factory ignition systems and none of the parts have even been replaced.. I'm only referring to chainsaws. I do the Briggs electronic MAGNETRON coil convert on small briggs engines with excellent results but I'm not a fan of aftermarket electronic ignition systems. (and I'm a electronic tech and journeyman electrician)

On Homelites EZ's the electronic MAGNETO coils require a opposite polarity flywheel.

The NOVA chips that have 2 terminals that replace points condensers do not require opposite polarity flywheel normally because you just reverse the connection to the chip to reverse the polarity. (but I do not like NOVA chips for long term reliability) The old NLA Atom chips were the better ones (more reliable) but one size does not fit all with those

If you ever install a replacement flywheel or magneto and the saw won't start a quick way to tell if the polarity of the flywheel magnets is wrong take the spark plug out and ground it good and then take a variable speed drill and spin the engine in both directions and one of the directions the spark will be stronger and if the spark is stronger when going opposite direction to the NORMAL direction that saw runs, it wants a opposite polarity flywheel or it has the wrong magneto for that flywheel.

If you are not getting a ignition run on your saw or spark you could get a 2 terminal Nova chip for less than $20 and just remove the wire coming from under the flywheel from the points and install it onto the chip and test and if you get a run you then know your points/condenser is PROBABLY bad or if no promise to run using both chip polarities then replace the magneto.

My old 028's require a special tool to gap the replacement points (I think) because the points lobe is on the flywheel. (if my memory has not failed me again)

I'm wondering why you do not want to remove the flywheel and look?
If you are not getting any spark you can take a ohmmeter and test the points for make and break with the kill switch off and slow rotate the engine flywheel by hand. (see the points make and break on the ohmmeter as very low ohms, one ohm or less)
I've seen old points magneto's check good on a ohmmeter (and on a coil tester) but not run most generally due to arc over carbon trails inside.

 

[scruffy808]

Hi; my question is can any of these chips ( used to replace the points & cond ) be used with out changing the flywheel ? My saw is originally points/cond and I have seen somewhere that to change to electronic ign. requires a different flywheel
Also, thanks to Scruffy for the comments on changing the timing
and to Okie for comments on coils & timing.
My 031 is still not running as I suspect a bad coil. The primary & secondary resistances check out but I suspect a fault.
Thanks to all .

Hey again oldercut, See my other reply to you- my 031 ran its original flywheel WITHOUT the points using the Atom Brown "computer ignition" module. Ran for many years no problems as Atom (Australian designed) was sold as a dropin replacement module. Different colors depending on application, brown for chainsaws. My problem started when aftermarket coil was fitted. Somehow timing now badly retarded. You could well be correct- some electronic modules require a different flywheel, but can 100% say it will work fine BUT combination of coil characteristics and electronics can change timing.

 

[KASH]

I have installed several Nova knock offs from Princess Auto that have been in service for 5 years or better.I like the Kawasaki ones best I am going to try a couple that I know are good from Partner chain saws.
Kash

 

[Okie]

Lots of info on-line about converting the 031 to electronic and/or using a module to replace the points/condenser.

 

[chy_farm]

-----------
Step 4- Pull flywheel off, discard woodruff key. Retard flywheel position on crank, a small amount reassemble recheck timing.
Only a few degrees may be needed to stop kickback - -----------------

Good evening Scruffy, thank you for this information.
One question is, which way do you mean retard?
Most of our saws spin counterclocwise when we see flywheel. So my thought is that this retard means you spin the flywheel clocwise a little.
Is this right?
Thank you in advance,

Chy

 

[leaf]

Good evening Scruffy, thank you for this information.
One question is, which way do you mean retard?
Most of our saws spin counterclocwise when we see flywheel. So my thought is that this retard means you spin the flywheel clocwise a little.
Is this right?
Thank you in advance,

Chy

"spin" is an odd word in context. If the flywheel is mounted on the crankshaft so that the magnets in the flywheel get to the coil assembly sooner in the rotational path, then the timing is advanced. If the magnets get to the coil later, retarded. (Do remember, the spark occurs at some time before top dead center.) So, yes, given a certain rotational position of the crankshaft if the magnets are more clockwise after adjustment, the timing is retarded.

 

[Old2stroke]

I have been modifying timing for many years in attempts to make non-oem coils work on various saws and my "ballpark" experience would say that timing at low rpm that gives up to 15 deg BTDC should not cause any kickback issues when cranking, once you get over 20 deg there could be some kickback but a lot seems to be dependent on the particular saw, many older saws with fixed magneto ignition were set close to 30 deg BTDC and didn't seem to have kickback issues. Just to clarify a point, electronic coils cannot advance the timing. The maximum timing is determined by the position of the FW magnets relative to the coil and TDC, the coil can only retard the timing from this point. To retard the timing the FW must be moved clockwise when looking at the FW. Of all the after market components available for saws, the coils have been the most frustrating, they seldom have a timing curve that matches the OEM ones.

 

[chy_farm]

Thanks Leaf and Old2stroke, appreciate your info. My project is Stihl 084, an old one. Her ignition did not make sparks so tried to fabricate another one on my own. This new unit works good so setting the timing will be next job to me.