Improving Auto-Clutch Grip?

Discussion in 'Whizzer Motorized Bicycles' started by Hal the Elder, Dec 23, 2008.

  1. Hal the Elder

    Hal the Elder Member


    I've got my auto-clutch removed from the bike for changing the rear belt.

    While I'm at it, I plan to de-glaze the shoes and then mount the clutch drum in my lathe to give the inner shoe-contacting surface a better grip by giving it a slightly rougher surface with emery cloth or sandpaper.

    Is this a bad idea?

    I rely on you experts for your comments, as my wife doesn't want to commit to an opinion.


    Attached Files:

  2. Slippery Clutch blues!

    Hi Hal, I would simply remove the glaze, where present. The goal is to simulate the old practice (yeah I did the brake shoes for the '39 Merc I drove to High School) of "Arc Grinding" the shoes, so they matched the ID of the newly turned drums.

    Admittedly, I do not remember how to set up the Brake Lathe to do this BUT Arc Grinding would be the right technic (Tek-Neek), I would NOT remove, nor rough up the clutch drum, I would NOT want to increase it's diameter, as that is counter-productive. Simply match the Shoe OD to the Drum's ID.

    Yeah, I too am getting old........

  3. Hal the Elder

    Hal the Elder Member

    Hey Enginebike Mike:

    The 1939 Merc was the first Mercury to be built by FoMoCo.

    Up until then, it was only Ford and Lincoln.

    (We don't wanna talk about the Edsel, do we?) :icon_cry:

    BTW...Should I wait for my replacement Hi-Flow or bore out the baffles in my stock muffler?

    Last edited: Dec 24, 2008
  4. n8ygn

    n8ygn Member

    Hal, I don't have an answer but an observation. It does look as though your clutch pads are touching the drum unevenly in the picture you sent. Maybe just the shoe would be best, to get full contact with the drum. Let me know what you do I was considering doing the same thing. Dane
  5. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Hal, First a question....... Is that a seal or a bearing still sitting on the bearing race? It also looks like the bearing race is becoming worn.
    I just completed rebuilding the last 40 hubs in stock and discovered a 100% failure rate with the current production hub [you don't have the current version]. Because my rebuild price was based on a "rebuildable hub" exchange program, I won't be able to credit the current production hub after Jan 2009. The reason the current version can not survive the rebuild process centers around 2 major engineering glitches. For some reason, which I don't understand, the current version has deepened the bearing cavity and added additional spacers and bearings on both sides of the hub. Adding additional #6901Z bearings is something I am puzzled about, because I have never replaced the #6901Z bearing unless someone over-tightened them and caused the center to crush the outer bearing housing. I asked Whizzer to install a hard spacer between the bearings on the early clutch to avoid damaging the bearings during the installation process, sadly they used some kind of soft peice of tubing that didn't help. Because the current version offers more bearings seperated with some type of spacer which will not help if over tightened during the install process either. One serious problem surfaced because the bearing area was increased to allow room for the extra bearing and spacer, but also reduced the hub area that was needed to support the bearing race shaft and the hub. Although difficult to explain, the following result will hopefully make sense. When I pressed [by hand only] the two sides of a new clutch together, the center bearing race broke loose from the hub. During a later rebuild on one of the current versions the hub snapped off during the process of pressing on the new hardened bearing sleeve. After 2 problems in a row, I took a closer look and the reason the center was breaking from the hub is because of the deeper bearing pockets. There is only approx. 1/8" of metal connecting the bearing ramp and hub. I will attach a picture to show the contact area.
    The next problem concerns the change in the pulley on the hub. In the past the pulley was part of the actual hub, however it is now a seperate part and attached via 2 roll pins, it is important to note the roll pins only extend into the holes in the hub a very small amount, and during testing the pulley worked loose and enlogated the small holes. I haven't measured the depth of the holes, but I would gess less than 1/8" [.125"]. The only problem with this system is when the pulley loosens, it spins on the hub, and the motorbike stops its forward motion.

    As far as you cutting the inner drum, don't be real sure the bearing ramp, center hole, bearings, and inner hub are in correct alignment. On some of the hubs I just finished I found several where the bearing surface wasn't parallel, so I advise you to use a dial indicater on the bearing surface for alingment prior to cutting the hub.

    Merry Christmas,

    Attached Files:

    Last edited: Dec 25, 2008
  6. Hal the Elder

    Hal the Elder Member

    I'm sorry, but I don't know if that was a seal or a bearing on the bearing race of my clutch drum. The clutch is back on the bike now.

    Also, my intention was not to do any "cutting" or machining of the inner drum shoe contact area, but only to abrade it with emery cloth to give it a slightly rougher, more friction-producing surface to mate with the clutch shoes.

    I bought new belts for Oscar, but I bought an A-27 for the primary belt, like the stock belt, but I noticed on one of your photos that your primary belt is a COG belt, which is an AX-27, not an A-27.

    Should I return the plain belt and get a cog belt? My secondary belt is an AX-62 cog belt.

    Gates belts are not available anywhere in my High Desert area.

    Even the local Gates distributor has no AX-62 belts in his order catalog, so I went to a Bearing/Sprocket/Belt Industrial Supply House and he said that Goodyear belts were every bit as good a Gates belts, so that's what I bought.

    That picture of the clutch drum looks like a total disaster!

    Thanks...and I hope you had a Merry Christmas!
    Last edited: Dec 25, 2008
  7. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Hal, The AX27 belts I have in stock are from NAP auto parts but were made by gates. The AX series are notched belts, and will work much better.

    Have fun,

    Attached Files:

    Last edited: Dec 25, 2008
  8. Auto clutch

    After 2 failed autos Quenton rebuilt mine with the hardened race. It still slipped a little (sorry Q) In desperation I did the deed of dual. The deed. I put the manual lever back on, so it would idle without engaging the auto. Then before installing it I lightly sandblasted the inner housing / you could get the same result by lightly sanding with emery. It then became a different animal.. This beast engages like it was born to run. Sorry if I gave away any dirt track secrets, and maybe it will decrease the life of the shoes but I'm happy now. It WORKS>>>>>for me.
  9. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Zomby, The shoes will most likely last longer because they will slip less during engagement. Because of quality control issues almost all the clutches are slightly different, but the secret is to have the hardened sleeve and have 90% or better of each shoe contacting the hub. I like the idea of using a sandblaster on the inner hub and will try it on my next personal clutch setup. I also have the clutch lever and cable still hooked up on my 1999 model.

    Have fun,
  10. btr

    btr New Member

    Hey Zomby, I had the same problem of slower take offs during last 3 rides which was getting worse. Motor was revving strong but no movement at take off which I had 200 miles ago. Cruising low and top speeds are still great. I just sanded the shoes and hub which was like a mirror inside. I’m testing it tomorrow but did sandblasting last for a while? If sandpaper doesn’t work well I may take it to a place to get it sandblasted. Need to get this done to ride to “scooter & other motorized bike show” in downtown Atlanta next month.
  11. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Sandblast the inner hub! Be sure to remove any ledge left by the edge of the shoes. The ledge can cause the shoes to seat improperly. If you don't have access to a sandblaster use a Dremel grinder and create a rough cross pattern inside the hub.

    Have fun,