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  • Ryobi flywheel fix...

    Did not want to interrupt the other ryobi thread any more with repair issues after already littering it up with my diagnostics,,,

    anyways - flywheel key was sheared, and it's simply an aluminum (or was) protrusion of the flywheel material itself that fit into a .125" crank key cut out (kinda half moon) in the crank itself ---

    so the big dilemma was the fact that on each side of the original flywheel key sides for some reason ryobi has a vacant as seen in pic... probably to try to stop HSM guys from just broaching in a .125" slot in the flywheel and installing a regular key like normal people would have done in the first place...




    so I had to go oversize on the keys flywheel side - way oversize like .250,,,


    so I built me up a ryobi broach;



    chucked er up




    locked the brake (don't laugh the bungie works just fine although I could have used some help getting it back off)



    and the rest was shall we say history, oh - not quite - had to build the damn key...

  • #2
    So start broaching - cut like butter .010" a pass and pumping the quill makes quick work...



    get it to where I want it and call it good,,, don't have to go too deep, not like the things going to be holding a chevy front end together and if it did it would just be another recall anyways...



    removal of the flywheel reveals some nice verification "curlers" from my 15 degree rake of the home brew broach tool...



    as far as the keyway --- we don't want to talk about that too much as after machining it the fun stopped and skin is a little thin around the thumb and index fingers from the grinding wheel and then the hand stone...




    but; get it all back together and third pull she fires off and would not quit,,, would have started first pull but was all loaded up on fuel from improper ignition timing...

    Lot's of procedures to go through just to save a dang weedeater,,, but weedeaters are needed, so the resources saved with not too bad an effort and really nothing that I did not already own I think it time well spent...

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    • #3
      Hey nice fix AK, thanks for including the pics, helps explain the setup very well.
      Good diagnosis and thanks for saving the dump from taking in another fixable little orphaned engine that just needed some TLC from someone that cares.

      Sometimes I think the OEMs go out of their way to make things more difficult to repair only so that the public will buy a new one. The general public isn't as fortunate as most of us in our ability to save what most throw away. Hard to justify the cost to a paying customer, but for personal use it always makes me feel good being able to save something like you did.
      Home, down in the valley behind the Red Angus
      Bad Decisions Make Good Stories​

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      • #4
        I doubt it's an intentional embuggerance - there's probably a minimum specified radius on the mold, and having a clearance on either side of the keyway was probably the only way to guarantee the bore was clear for the corners of the key, without an additonal machining op on the bore.

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        • #5
          Originally posted by Sun God View Post
          I doubt it's an intentional embuggerance - there's probably a minimum specified radius on the mold, and having a clearance on either side of the keyway was probably the only way to guarantee the bore was clear for the corners of the key, without an additonal machining op on the bore.
          That plus the cutouts or clearance makes fora good shear pin effect, so it is just a cheap casting that breaks.
          Amount of experience is in direct proportion to the value of broken equipment.

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          • #6
            Originally posted by Sun God View Post
            embuggerance
            Excellent manufactured word..... will have to borrow that for future use... I can confidently expect it will have application.
            1601

            Keep eye on ball.
            Hashim Khan

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            • #7
              Thanks Willy, this thing had me starting to doubt myself but persistence paid off eventually,

              I triple checked everything and ignition timing was the only thing left but to tell you the truth the reason I didn't immediately go there is because I knew the basic layout, and first off weedeaters rarely stall out instantly and in fact they cant as they will just snap the line if it wraps, then there's the fact that they have a clutch that will allow them to slip if they ever did, then there's the fact that the flywheel is on the drive side (unlike most lawnmowers) so no stored momentum from the flywheel gets transmitted through the crank (or key) --- still - had to verify and glad I finally went into that end to check...

              Im in agreement with you that so many things are not only designed to fail but intentionally designed not to be fixed easy after failure, all you have to do is spend a little time in the bizz and you cannot ignore this obvious fact...

              but In this particular case Im also in agreement with SG as I think it more of a mold process in production, although it's an incredible amount of overkill clearance on each side of the key-form,,,

              I think the key wears as the flywheel gets a little loose even though the clutch drive is designed to keep tightening with direction of load,,, it was not on all that tight, therefore my conclusion is that the power impulses from the engine itself "fretted" away at the integral flywheel key till there was a release, talked to the bro last night and he verifies this, said it just quit running - no catastrophic stall out of any kind...

              welp - the "orphaned" weedeater hangs on the wall ready for use...

              NEXT! lol

              Comment


              • #8
                That's nice work!

                The key isn't for "driving" though - it's just to initially index the ignition/flywheel. You can just leave them out - clean dry taper, clean dry flywheel and correct torque is all it takes. Can be tricky to align (hence the key), and you should tap it with a socket to lock it before torque.

                If the flywheel was "loose", it may no longer have a valid taper. I'd toss it and get another (cheap). At 10-14k rpm, you don't want anything "loose".

                Keys have gone on most low end outdoor power tools now - usually there just a crude "nub" cast into the flywheel align with a slot in the crank.
                Last edited by lakeside53; 06-03-2014, 11:31 AM.

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                • #9
                  I would not trust it if it were not keyed - "large" part of taper starts out at a mere 1/2" diameter and the tapers length is only about a half inch deep...

                  every time you pull the cord to start you have to transfer this energy into the crank from the flywheel,,, and these little four strokes have quite a bit of compression,,, then once running think of all those little power strokes working on the flywheel through the crank... a good key is set it and forget it.

                  and then there's things like frequency migration, were as the flywheel will indeed move tighter onto the taper over time, but without a key and yet under consistent load think of it as spiral more than linear...
                  Last edited by A.K. Boomer; 06-03-2014, 11:56 AM.

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                  • #10
                    I've pulled a few thousand of weed-eater/chainsaw etc flywheels. It's amazing how tight they are on from the factory (especially the "short-fat tapers") if torqued down correctly; some come off with a "bang". The trick is clean clean clean. When we had a busted cast-in key, checked the fw for cracks and if ok, just lined it up "by eye", and torqued it down again. Why do they break or get loose? imo.. (ignoring the occasional factory f/u), because someone as in there at some point, levered it off with screwdrivers and never put it down at the correct setting. If it on right, the fw is actually "stretched" onto the taper.

                    It's "common" to leave the key out if you are messing with the factory timing. Lots of keyless "hopped up" chainsaws out there. Might even have one downstairs myself
                    Last edited by lakeside53; 06-03-2014, 12:05 PM.

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                    • #11
                      Originally posted by lakeside53 View Post
                      I've pulled a few thousand of weed-eater/chainsaw etc flywheels.
                      Dang --- you got me there, you know you could have chimed in in the other ryobi post when I stated I found the sheared key, I did think about heating it up some and throwing it back on with just loc-tight sleeve retainer but my luck would be that I would get it running and then find out the seal behind it was leaking and needed to be replaced lol

                      oh well - it's done and it's not coming uncorked for nuthin...

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                      • #12
                        Originally posted by Willy View Post
                        Sometimes I think the OEMs go out of their way to make things more difficult to repair only so that the public will buy a new one. The general public isn't as fortunate as most of us in our ability to save what most throw away. Hard to justify the cost to a paying customer, but for personal use it always makes me feel good being able to save something like you did.
                        Everything is built to a price point and that helps determine the ease (and cost) of repair vs replace.

                        Example: lot of Beechcraft Barons- a nice light twin engine aircraft- when to the scrap heap when the engines wore out. A full overhaul cost more than a newer aircraft.

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                        • #13
                          Nicely done A.K.. Doesn't your spindle brake lock by camming it up/down?

                          I thought I was the only cheap stard that would salvage something like that. lol.
                          I bought a complete chainsaw (in pieces) off of ebay for $12 that was listed "for parts only" because I have another one just like it. I figured it would provide at least a few good spare parts. When I got it i was thrilled that it still had good compression and wasn't seized up! Then I figured out why it was in pieces. The previous owner had run the saw with all of the mounting bolts loose that held the engine inside the case. It shook so bad that it broke off the ends of the mounting bosses on the engine cases. It also snapped off one of the cooling fins on the flywheel, which might have been the source of the original vibration problem. Chicken or the egg.....

                          I thought what the heck, why not? I built up the broken and wallowed out bosses with TIG and installed heli-coils to provide the new threads. Also built up a new cooling fin on the flywheel and shaped it with hand files. While it was apart I rebuilt the carb with a new kit as well. Dog gone thing runs better than the saw I was buying the parts for.

                          Last edited by Highpower; 06-03-2014, 01:14 PM. Reason: spelling

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                          • #14

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                            • #15
                              Originally posted by CarlByrns View Post
                              Everything is built to a price point and that helps determine the ease (and cost) of repair vs replace.

                              Yes Carl I very much agree and am aware of price point objectives and goals as far as marketing is concerned. As I said, a repair like AK performed, while very effective in restoring a product back into service is not viable from cost/benefit perspective when done commercially.

                              It's certain design features as well as the incorporation of security screws and certain assembly methods that thwart the average consumer from even having a look. They want you at the checkout buying a replacement, not at a parts counter buying a fuse.
                              Home, down in the valley behind the Red Angus
                              Bad Decisions Make Good Stories​

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