# Stihl FS45 trimmer flywheel woodruf key



## billyboy (Jan 9, 2022)

Usually started fairly easily, then it wouldn't, seemed like the closest thing to starting was a backfire. well the the woodruf key in the fly wheel is sheared. Is there a fix other than getting another flywheel. These are the molded in place type key. Very nice design!!


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## Chevboy0167 (Jan 9, 2022)

I'm sure it could be repaired with some machining work and finding a woodruff key. That would probably take more time and money than just buying a used OEM.









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## billyboy (Jan 9, 2022)

I did order a used one off ebay but i thought i saw a post about some guy filing a grove in the flywheel and jaming a wooden dowl in it. I agree trying to machine it would be spendy. Don't really want to take it all apart too many times either. Maybe the dam thing wasn't tight enough and it gave way. "Cheesey" best describes this key.


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## frank_ (Jan 10, 2022)

billyboy said:


> I did order a used one off ebay but i thought i saw a post about some guy filing a grove in the flywheel and jaming a wooden dowl in it. I agree trying to machine it would be spendy. Don't really want to take it all apart too many times either. Maybe the dam thing wasn't tight enough and it gave way. "Cheesey" best describes this key.


i needle filed a few, lightly fitted them, and drove a nail down the hole and cut the leftover nail off
mainly the mower ones that have an alloy shear key that avoids the crank bending if the blade hits a tree root or brick ,but also did a stihl sheared one


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## billyboy (Jan 10, 2022)

@frank_ pics or video the next time you do that, would be interesting, thanks


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## pioneerguy600 (Jan 10, 2022)

There is an actuall broaching tool to make a keyway in a flywheel but a hacksaw blade wrapped on one end with a ball of taspe works very well and quite quickly.


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## billyboy (Jan 10, 2022)

my dealer needed $90 for a flywheel but I got a used one coming for $14. Don't see how I can even stop to think about it for that kind of money. The hacksaw blade sounds good but I couldn't get my head around matching the divot in the shaft. Doesn't look big enough to hold more than a couple tears. Suppose a guy could make some sort of shaped form with wax. Last time I ran it was with plastic cutter blades and I try to avoid hard objects. Maybe I need to stick to line with it.

On another note, I have a FS90 and I would like to know if the valve cover is supposed to be air tight. Was going to adjust the valves and don't know if I should put new cork gasket in it or maybe some gasket sealer. Any help would be appreciated. Thanks


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## pioneerguy600 (Jan 10, 2022)

Since the keyway is only there to align the flywheel to the crankshaft for ignition purposes no key is actually required to hold the flywheel in place. The flywheel will stay where it is seated on the tapered crankshaft if tightened down properly. When I advance timing I often leave the key out of the equation, when swapping coils, modules and wiring in chips the timing for spark is often in need of adjustments. Once the proper timing is found then that is where I often cut a new keyway in a flywheel. In your case all you need to align the flywheel to the crank is a center punch, mark the flywheel, mark on the crank stub.


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## billyboy (Feb 5, 2022)

Can someone tell me what the resistance should be on this coil? I get 294 on the primary and 2182 on the secondary. Is there a substitute for the 4140 1303A coil?
I have replaced flywheel and carb and still no joy.


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## Chevboy0167 (Feb 5, 2022)

billyboy, look here....









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## billyboy (Feb 5, 2022)

Thank you


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## Chevboy0167 (Feb 5, 2022)

Yeppers. To add, using a multimeter ohm test alone on an electronic coil will not work. There is a transistor and capacitor inside that coil that need energized and triggered to operate. 

Now on an older saw with points and condenser, an ohm test works on the coil and the condenser.


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## billyboy (Feb 5, 2022)

I have a good blueish spark with the ground opened pretty wide on the plug and all I get is a what seems like a backfire. The legs of the ignition module are over the magnets at TDC. Don't know what else to do but try a coil.


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## frank_ (Feb 6, 2022)

billyboy said:


> I have a good blueish spark with the ground opened pretty wide on the plug and all I get is a what seems like a backfire. The legs of the ignition module are over the magnets at TDC. Don't know what else to do but try a coil.


i usually check the timing with a strobe, to avoid it being a moneypit
also i had one last year that would cough but not run, but ran ok with the muffler removed (was blocked)


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## billyboy (Feb 6, 2022)

I had the muffler off and flames shooting out 2 inches or more. Very low use on this machine. Pristine P&C. Got it out last spring and wouldn’t run. Took it to a Stihl dealer. He thought it was flywheel. Don’t have a timing light. Sparks very good with plug grounded on cylinder and with inline spark tester. Floods easy if choked too much.


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## billyboy (Feb 6, 2022)

*@chevyboy0167, Are you sure the 1305 will substitute for the1303A. One of the listings I found on eBay said it wouldn’t. Thanks*


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## Chevboy0167 (Feb 6, 2022)

Sorry Billy, I can not confirm it will. Was just what I found on the bay with a quick search. Somebody with Stihl IPL access could maybe confirm?


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## billyboy (Feb 6, 2022)

Oky dockie, found a used 1303A with a bit more searching, Thanks


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## billyboy (Feb 11, 2022)

Update here, I got a used coil off ebay and it started with a couple cranks. Put the old carb back on and it ran on it too. All that mucking around and all it needed was a coil. Dang. It would have been so easy just replacing the coil first. Oh well, $40 in new and used parts and it lives. And I have a new spare carb sitting here for it.


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## Rein (Feb 25, 2022)

billyboy said:


> Update here, I got a used coil off ebay and it started with a couple cranks. Put the old carb back on and it ran on it too. All that mucking around and all it needed was a coil. Dang. It would have been so easy just replacing the coil first. Oh well, $40 in new and used parts and it lives. And I have a new spare carb sitting here for it.


So how is it running with what you described as a sheared key? Did you just align the flywheel with the crank slot and tighten it down?


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## Rein (Feb 25, 2022)

pioneerguy600 said:


> Since the keyway is only there to align the flywheel to the crankshaft for ignition purposes no key is actually required to hold the flywheel in place. The flywheel will stay where it is seated on the tapered crankshaft if tightened down properly. When I advance timing I often leave the key out of the equation, when swapping coils, modules and wiring in chips the timing for spark is often in need of adjustments. Once the proper timing is found then that is where I often cut a new keyway in a flywheel. In your case all you need to align the flywheel to the crank is a center punch, mark the flywheel, mark on the crank stub.


I have a Poulan 3314 which kicked back on pull starting a lot, although I did manage to get it running sometimes. I swapped out the flywheel with no success. I found that although the cast in key was intact with no marks of any kind there was about 5 degrees of play between the flywheel and the crankshaft. I've since relegated that saw to my parts box but some day I'd like to revisit it and solve that one problem. I did confirm the magneto was working (used it on another saw I sold running in excellent condition). Do you know of any specific YouTube videos which show some or any of what you just described? When you advance timing are you doing it by trial and error or some other more sophisticated method? Are you using a degree wheel, timing light or machinist's tools for any of that work? How do you cut a new keyway?


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## billyboy (Feb 25, 2022)

@Rein, I got a used flywheel off eBay. Which wasn’t my problem with getting it running. It Was my coil that was defective. From what I have read on arboristsite the guys that advance timing are cutting about .020 off the key. I have seen guys on YouTube use a timing light on a saw. I think that the magnets on the flywheel need to line up with the legs of the coil. As pioneer 600 said above mark the key way on the shaft and the key on the flywheel and your good to go. Make sure both surfaces are clean. I used a socket and gave it a few light wacks to seat it. Screwing the clutch down might move it otherwise with no key. Most guys use a degree wheel . Have you checked to see if it’s flooding as that might give you what seems like a kickback. I have read here that sometimes you can’t pull a saw over if It’s flooded real bad. Porting and messing with timing is a bit beyond my wheelhouse. Hope this helps.


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## pioneerguy600 (Feb 25, 2022)

Rein said:


> I have a Poulan 3314 which kicked back on pull starting a lot, although I did manage to get it running sometimes. I swapped out the flywheel with no success. I found that although the cast in key was intact with no marks of any kind there was about 5 degrees of play between the flywheel and the crankshaft. I've since relegated that saw to my parts box but some day I'd like to revisit it and solve that one problem. I did confirm the magneto was working (used it on another saw I sold running in excellent condition). Do you know of any specific YouTube videos which show some or any of what you just described? When you advance timing are you doing it by trial and error or some other more sophisticated method? Are you using a degree wheel, timing light or machinist's tools for any of that work? How do you cut a new keyway?


 Sorry on the Youtube video`s, I never watch them. I use both degree wheel, timing light and a top dead center stop along with the published spark timing from the manufacturers.The keyway can be re cut with a simple hacksaw blade and file but there is a professional re broaching setup that can cut a keyway with precision. Even stock manufactured flywheels have some slight timing error and then couple that with modules with timing retard for starting, then advancing as the RPM builds they can be off several - many degrees.


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## Rein (Feb 28, 2022)

pioneerguy600 said:


> Sorry on the Youtube video`s, I never watch them. I use both degree wheel, timing light and a top dead center stop along with the published spark timing from the manufacturers.The keyway can be re cut with a simple hacksaw blade and file but there is a professional re broaching setup that can cut a keyway with precision. Even stock manufactured flywheels have some slight timing error and then couple that with modules with timing retard for starting, then advancing as the RPM builds they can be off several - many degrees.


Thanks very much for that info! I never heard of broaching before but did a little YouTube searching and turned up several videos, like this -  - which, although somewhat DIY, does show how it's accomplished and the tools involved. I've always wanted a manual press like that so maybe I'll start asking on FreeCycle and Facebook channels to pick up a used one as well as investigate where to purchase broach tools specific to most of the keyways for chainsaws, lawnmowers, etc. I'm also going to search "using a timing light on a chainsaw" on YouTube since I haven't seen that operation yet. I've watched plenty of guys showing the use of degree wheels, piston stops, etc., so my knowledge is growing, little by little, to understand this whole process and the theory of operation for small engine timing. I have watched a lot of videos dealing with kickback and causes in various categories of machines. It seems like ones with the timing slightly off is one of the more common causes (due to the engine being stopped violently for one reason or another) and the reason is invariably due to the keyway becoming misaligned to the flywheel. Thanks again!


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## frank_ (Feb 28, 2022)

Rein said:


> Thanks very much for that info! I never heard of broaching before but did a little YouTube searching and turned up several videos, like this -  - which, although somewhat DIY, does show how it's accomplished and the tools involved. I've always wanted a manual press like that so maybe I'll start asking on FreeCycle and Facebook channels to pick up a used one as well as investigate where to purchase broach tools specific to most of the keyways for chainsaws, lawnmowers, etc. I'm also going to search "using a timing light on a chainsaw" on YouTube since I haven't seen that operation yet. I've watched plenty of guys showing the use of degree wheels, piston stops, etc., so my knowledge is growing, little by little, to understand this whole process and the theory of operation for small engine timing. I have watched a lot of videos dealing with kickback and causes in various categories of machines. It seems like ones with the timing slightly off is one of the more common causes (due to the engine being stopped violently for one reason or another) and the reason is invariably due to the keyway becoming misaligned to the flywheel. Thanks again!



i spin them with a drill and marker pen to test the timing light personally, the electronic coils are usually 0 deg at cranking speed


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## Rein (Feb 28, 2022)

billyboy said:


> @Rein, I got a used flywheel off eBay. Which wasn’t my problem with getting it running. It Was my coil that was defective. From what I have read on arboristsite the guys that advance timing are cutting about .020 off the key. I have seen guys on YouTube use a timing light on a saw. I think that the magnets on the flywheel need to line up with the legs of the coil. As pioneer 600 said above mark the key way on the shaft and the key on the flywheel and your good to go. Make sure both surfaces are clean. I used a socket and gave it a few light wacks to seat it. Screwing the clutch down might move it otherwise with no key. Most guys use a degree wheel . Have you checked to see if it’s flooding as that might give you what seems like a kickback. I have read here that sometimes you can’t pull a saw over if It’s flooded real bad. Porting and messing with timing is a bit beyond my wheelhouse. Hope this helps.


Thanks. Yes, I checked to make sure I wasn't flooding, which can cause the engine to vapor lock. That's a good idea to use a socket to seat the flywheel securely before tightening down and I may do that to start, just to see if I can move the timing enough with no keyway/key modifications. I want to go a step further than that though - see my reply to pioneerguy600.


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## Rein (Feb 28, 2022)

frank_ said:


> i spin them with a drill and marker pen to test the timing light personally, the electronic coils are usually 0 deg at cranking speed


Thanks! I haven't watched any timing light videos yet so I'm drawing a blank, but as soon as I do I'll remember what you said and see how that applies to the process.


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