Swing arm bolt torque spec???

[MichiganBrian]

On this B+ project, when I tighten swing arm bolt, swing arm won’t move. I have To loosen it considerably in order For swing arm to move. Is there a torque spec for bolt?
Brian

[Bullfrog]

On all Hodakas up through the Model 96 (toaster tank) Dirt Squirt, the swing arm pivot design uses a "unitized" 3-part bushing at the swing arm pivot. There is an outer steel sleeve which is a (tight) press fit in the frame bosses. Then a firm rubber sleeve which is "welded" to the outer steel sleeve AND the inner steel sleeve. Flexing of the rubber provides for ALL of the intended movement of the swing arm. Finally, there is an inner steel sleeve which is meant to be "pinched" between the frame and the "end caps" mounted on either side of the swing arm at the pivot point.

When all parts are working properly, ALL up/down rotational movement of the swing arm happens by "rotational flexing" of the rubber sleeves "welded" into the bushings. As a result, when the swing arm pivot bolt is properly tightened (ie, tight -- and no, I don't have a torque spec. for you), the swing arm will stay in position when you remove the shocks. You will find that the swing arm will move (rotate) up and down if you grab the axle end plate and put some force to it. The swing arm will not drop down freely. This is normal on your Hodaka.

Ed

[MichiganBrian]

Thank you for info. Pretty primitive technology no?? I assumed it was a bearing of some kind, so I bought new bushings. Obviously not needed.

[Bullfrog]

. . . also maintenance free.

[JPark]

The same sort of system is used in car suspension arms. Trouble can occur if you tighten the bushings down when the arm is dropped outside its normal range of motion thereby causing it to distort the rubber more than it is designed for.
I'm of the opinion that the bushings should be tightened down with someone sitting on the bike so that the rubber is normally relaxed as you are riding.

There may be some merit to a theory that the reversal of distortion is not good and that tightening with the shock extended is a better way. What amazes me is how so many of these bushings can be still functional after a half century, but they are encapsulated in steel and only exposed on the faces.

On a bike this light, rubber can work really well, but with more weight and power it seems that bearings and all the lubrication and corrosion hassles that go with them are the only way.

[Bullfrog]

Good review of features/characteristics. Additionally, longevity tends to indicate the swing arm bushings are operating well under stress limits for the rubber deflection. Also, really good riders can feel the "flex" inherent with this type of bushing . . . I can't discern it. (Which tells you something about my level of riding expertise.)
Ed

[dirty_rat]

Late 1960's and early 1970's Maico's had a similar set-up for their swingarm. The biggest difference was that the bushings were installed in the swingarm itself and the axle bolt tightened the frame inward to give the proper flex to the bushings.

[Stever]

"Post by Bullfrog » Thu Jun 18, 2020 7:13 pm

. . . also maintenance free."

Yes indeed, and even after years of sitting! When it does the job, simple is beautiful.

-Steve R.