Help w/ replacing "ignition module" on Jonsered 70E

[zuren]

Tonight I began working on my dad's old chainsaw. It was diagnosed with having a bad electronic control unit and I was able to find one, so I started taking the thing apart until I got stuck...

Here is the carnage taking place...

Here is where I got stuck. I believe the cylinder on the shaft is part of the clutch mechanism, is it not (circular part centered in the pic)?

The nut holding it on was torqued quite tight. My question is: how does it come off......pull straight up with a gear puller?

I can't see any fasteners that look to be holding it on, so I wanted confirmation before moving forward.

Thanks for any help!

 

[bama]

I have pulled the flywheels off a 621 and a 920. They are different in appearance than this one, but it looks like yours has some threads beside the recoil springs(like mine did). If it is similar to mine, then you find a metal plate(3/16" thick and about 3-4" square works well) and drill holes that match up with those bolt holes(there should be three of them). This plate will rest flat on top of the crankshaft(above the flywheel). Next, you need to find(purchase) three bolts that match the threads of those holes(in the flywheel) and extend all the way through the plate(except for the boltheads) and into all of the threads of the holes in the flywheel. Don't get too long of bolts or you will puncture something behind the flywheel.

As you draw down the tension in these three bolts, that will pull the flywheel up and off. It will probably give a "pop" and then it will be released. The concept is the same on many of the old Briggs motors I have worked on.

I hope this makes sense. It would be much easier to show than to write it down. I know that you are to never use a puller on a Briggs motor(or bad things happen), so I would assume you should not use one on this saw. Otherwise, you will be looking for a new flywheel as well.

Good Luck.

 

[bama]

Just wanted to clarify that you should use the three holes CLOSEST to the center of the flywheel.

 

[Chris J.]

I haven't yet gotten into my Jred 70, but that flywheel is nothing like the ones in my 670s or my 801. Keep us posted on your progress.

 

[zuren]

I'll have to clean those holes up toward the center of the flywheel and see if they are threaded. I've been using a heavy duty paperclip opened up to probe and clean saw dust out of tight places, and I don't remember feeling any threads there.

bama - Your directions were very clear and make complete sense! Basically, what you are describing is the same motion as a gear puller, only you are using bolts and the holes provided to keep the force more centered, rather than on the edges.

 

[bama]

If there aren't threads on those holes, then I could only guess that you would use the threaded holes on the outside of the flywheel(looks like there are four?). But, before I would do that, I would post that question again to get confirmation.

Glad the instructions made sense. Keep us posted on how it turns out.

 

[zuren]

Keep us posted on how it turns out.

I got some 1/4" welding plate steel from Lowe's and some hex head screws from the corner hardware store. I was able to use M5x20 (.80 pitch) but I would use M5x25 next time, the 20s barely reached the threads. To drill, I marked each spot, used 3-in-1 oil as a cutting lube and knocked 3 holes in the plate. Using a socket and 1/4 turns, the flywheel came off perfectly with little resistance! I'll post pictures later this evening.

 

[bama]

Sounds like it worked the way it was supposed to. Save that plate! I use my plate for other saws and just drill different holes to fit each one. It saves tool space(for someone as cheap as me). I'm glad it turned out for you.