Stihl FS45 trimmer flywheel woodruf key

[Rein]

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?

 

[billyboy]

@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.

 

[pioneerguy600]

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.

 

[Rein]

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!

 

[frank_]

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

 

[Rein]

@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.

 

[Rein]

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.

 

[farmhard]

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!!

$10-15 on fleabay. I have lots of them but I'm in Canada right now and the shipping is way too high vs domestic. They aren't bad to change.