Stihl FS 46 String Trimmer Problem

[Fish]

I had a new block that the crankshaft was off @ 90 degrees, so I sent the customer another, plus some freebies for his trouble. I told him to keep the old block for parts. I was curious about the internals of the block, but not enough to pay the return shipping.

 

[DustGrind]

Timing is the problem. There is nothing else out there. Process of elimination. Fish also knows what he is doing.

I'm sorry. Just read where someone was going to send you a new flywheel. Thought that was very generous of him, then read where you said it may not run.
I'm just learning here. Sorry.
Didn't mean to offend you.

 

[Wood Doctor]

I had a new block that the crankshaft was off @ 90 degrees, so I sent the customer another, plus some freebies for his trouble. I told him to keep the old block for parts. I was curious about the internals of the block, but not enough to pay the return shipping.

Well, there is no shipping involved here. My curiosity and time is the only price I have to pay. If it all fails, I'll keep the parts. Heck, I imagine a Stihl dealer already quoted him a $200 repair price or condemned it.

 

[Fish]

well, popping on a brand new block for $30, he could hopefully handle.

 

[backhoelover]

i might have a good used flywheel can you send a pic? you can have it of course

 

[backhoelover]

that flywheel fits 45 different models anything mm fs hl km fc 55,38,45 will work

 

[Wood Doctor]

I suppose what worries me most is safely removing the flywheel after I pull the engine from the case. I've done this many times with chainsaws but never with a string trimmer engine. I'm assuming that there is a timing key for proper positioning that is likely sheared off.

 

[Fish]

First thing will be the clutch drum.

 

[Fish]

Then the clutch, I just clamp it in a bench vice and turn the flywheel.

 

[Fish]

Then I use a deepwell socket on the clutch, and whack it with a hammer to dislodge the flywheel.

 

[AVB]

For flywheel removal on of these and other 2 cycles I use one of these flywheel knockers. I had two of these made for the two different thread patterns that I commonly run into. So much better than banging on the clutches. Less chance of striking the crankshaft end with a hammer. With either method you back about one turn from seated to allow room for the flywheel to unseat.

 

[Wood Doctor]

I note that Fish left on the carb after removing the fuel tank. Makes sense because the carb is secure and the fuel lines can be removed together with the tank.

I have a 3-arm device that can pull the flywheel slowly. I'l try that first after removing the clutch drum and clutch. Those might be tougher than removing the flywheel.

Looks like there is a timing key on the shaft. It will be interesting to see if that sheared in this engine or if another mechanic failed to tighten the nut and set up the flywheel slippage or never even thought about the timing issue. I'll be sure to post results. Give me some slack on this because I want to be careful and take a few good Pics.

 

[Fish]

I tear down @ 1 of these a week in the summer months..
Takes 5-10 minutes. I just snapped pics of various blocks, the carb/tank still on thing was purely by chance, no plan involved.
I just yank off the part needed to ship, I have a chitload of blocks/parts laying about.

 

[AVB]

I have a 3-arm device that can pull the flywheel slowly.

I believe once you try the flywheel knocker you'll find it works much better than a puller. Besides on many chainsaws you simply can not get a puller in there to even grip the flywheel. I use a 2# brass and the knocker and it only takes a few taps to jar the flywheel loose , usually one or two. Sure saves taking all the cover off.

 

[Fish]

I have always been a BIG fan of knockers!!!

 

[Termitebuffet]

I have always been a fan of BIG knockers!!!

Fixed [emoji2] [emoji2]

 

[Fish]

Fixed [emoji2] [emoji2]

Just took a little playing with......

 

[Wood Doctor]

OK, guys, here's the latest on the FS 46. I decided to remove the carb while working. I pulled the engine and removed the flywheel. Yes, the index timing key was sheared off. I used what was left on the flywheel keyway to align the flywheel. I was careful not to let the engine move while I tightened it back up.

I tightened the clutch a bundle, making sure that the engine, flywheel, and drive shaft did not shift. Note that with the ignition module mounted to the engine, this is a must. On chain saws, the IM is secure to the case along with the engine and a flywheel nut moves to tighten it. That luxury is not available here.

Engine started and ran, a little shaky at first, but then it smoothed out. It still has some shaking at low speed, so I may be off the ideal timing angle a few degrees. Top end power and speed is excellent, and it accelerates up rather nicely. This line trimmer has now been saved from the landfill. The owner will probably be in shock that the engine runs again.

Oh, and BTW, the hardest part of the job was reassembling the plastic top with all the controls (wires, throttle, trigger, springs, etc.). Awkward as all get out, I figure that doubled my work time.

 

[Fish]

That is why I sell the bottom half and all of the innards as one part [except for the throttle cable] ....

 

[Wood Doctor]

That release that allows the bottom trigger to work (and the fast idle catch) is a real gem. It pops up loose too easily and its own spring will knock it right out. The other real monster turned out to be the trigger itself and yet another spring that enjoys coming loose. If either of those two small springs fails or is not installed right, the whole mechanism will not operate properly.

Then the two switch wires on the trimmer I worked on were supposed to travel along the top right edge where barely enough clearance was available. And, all of this had to be done with the engine and long pole in place. I used a small C-clamp to help out, but that seemed a bit make shift.

After it was all over, I was thankful for a night time Aleve tablet.