Hi Hal,
Here is a lot of important information on the Whizzer automatic clutch. It is possible to acheive "quick" and "total" lock [my dirt track Whizzer will easily pull wheelies, ask around for pictures], but that isn't the way it normally works. Because of the design, the clutch "slides" into lock, and normally slips when first engaged. If you advance the throttle quickly before the shoes are mated with the hub it will glaze the shoes and the only fix is to remove the glaze [Dremel grinder with a sanding drum] from the shoes. Problem is, once the shoes are glazed it will continue to slip. There were many different version of the shoes used in production, however the object remains the same. The more of the shoe you get to mate with the hub, the better the engagement. My hi-performance Whizzers have 99% to 100% contact, and some of the production clutches start out at less than 15%. I will tell you how I speed up the mating surfaces, but I don't suggest you do it this way. I lock the brakes, open the throttle until the clutch "smokes" a little, then re-surface the shoes [remove only the glazed area on each shoe], and repeat this process until most or all of each shoe is glazed, I then remove the glaze, and the clutch works really well. I would guess if done easily [not my way] it might take 20 or more times to reach 75% contact on some versions of the clutch. It is also important that you don't use my method on some of the earlier versions of the clutch because it could end up with undesired results. On the very early [all out of warranty by now] versions of the clutch, the shoe pivot pins didn't go all the way through the hub [hub was cast iron], and some of the pins could pull out of the hub, and I don't need to go into detail about the possible end result. The next version still used the cast iron hub, but the pins were pressed all the way throught the hub, but some still ended up with loose pins because of the way the pins were "peened" on the hub [most, if not all, are now out of warranty]. The next version still used the cast iron hub but the pins were flattened at the exit point on the outside of the hub [most, if not all are now out of warranty], as far as I know none of the shoe mounting pins ever worked loose on this or any future version. If the pins are loose on the earlier versions, a simple fix is possible. I am still using one of the earlier versions on my 1999 Whizzer that I modified to correct the loose pin problem. If the version doesn't have the holes all the way through the hub, drill the hole through with a 13/64" drill [can get away with using a 3/16" in a bind], then thread with a 1/4" X 20 tap. Next purchase 1/4" shoulder bolts, so that the shoulder matches the length of the hole in the shoe [may need to open the hole in each shoe if the fit is too tight to pivot], then thread the bolt throught the recently cut threads, and use a 1/4" X 20 nut to "lock" the bolt in place, cut off any extra threads extended past the jam nut. If the holes are already through the hub with loose pins, you just skip the part about drilling the hole through. Next I will cover the shoes used during the process, but it must be noted many of the similar style clutches [not Whizzer] with shoes on a pivot didin't have any material on the shoes, but were metal to metal contact. The shoes on the earlier Whizzer clutches had a very thin, but wider contact surface bonded [glued] to the shoes, the later versions added a thicker contact material, but weren't as wide. Some of the shoes had material attached with a taper cut, and some were cut even, therefore some took longer to "mate" with the hub than did others. It is important to note that my 1999 model is using the shoes with the thin, but wider shoe material, and it "hooks" up really well [over 68 MPH on a dyno]. The clutch on my dirt track racer uses the later clutch with the aluminum hub, and the shoes with the thicker but narrow material, and it can pull wheelies [works very well]. Another important change in the Whizzer clutch system concerned the bolt that mounts the clutch to the arm, the early version used regular threads, but early in production the mounting bolt was changed to reverse threads. It is very important that you know which version is used because if over tightened the bearing centers could be crushed and destroy the bearings [#6901Z available from any bearing company], Whizzer installed a sleeve between the bearings, but it isn't strong enought to overcome the power of a good socket wrench [not their fault we are so strong]. Later versions of the clutch added more bearings [some used as many as 5 instead of 2], however I prefer the version with only 2 bearings because the hub structure is more solid on both ends of the bearing sleeve area, and I now have a couple in my collection with the bearing race snapped from the hub [ a problem I doubt many will ever see]. Most of the Whizzer automatic clutches used a 3 section bearing and a seal on each end [my favorite version], but the latest editions removed the seals, replaced the 3 section needle bearing with a single one-way version, and installed a larger caged bearing on each side. Recently I modified 51 clutch hubs [installed a rockwell 58 rated bearing sleeve on each], and found the bearing surface in many different configerations. Some of the bearing surfaces were cast iron with no bearing sleeve, some had a bearing sleeve installed, but looked like it was cut on a lathe [rought tool marks], and one had a hardened bearing sleeve. All of the clutches I rebuilt were out of warranty, so I will gladly furnish the needed information if anyone wants to upgrade their own clutches [as a few have already done]. The bearing sleeve is 38.5 MM long, the O.D. is 30 MM, and the I.D. is 25 MM and needs to be high quality, highly polished, and rated at rockwell 58. On the hubs with sleeves installed, the sleeve needs to be removed [slow process on the lathe], but an additional 1 MM must be cut from the remaining surface in order for the new sleeve to be installed. The fit needs to be at least .002" interference and should be installed with a high grade retaining loc-tite [I use # 620 or #640]. It is also necessary to shorten the sleeve on both ends prior to pressing it on the hub [reduce from 38.5 MM to 36 MM].
One of the most common problems is the clutch not engaging during forward movement of the rear wheel. If the one way bearing dosen't lock on the sleeve it is impossible to start the motor [unless you own a Ambassador with the electric starter]. I have found several reasons for the clutch to "forget" to lock the one-way bearing. The most common is the bearing sleeve, the second is a defective one-way bearing, and lastly the single section one-way bearing slipping inside the aluminum hub [only on versions with the caged outside bearings]. I suggest the bearing sleeves be replaced on all versions of the clutch [problem #1 solved], replace the defective 3 section bearing with a new one [problem #2 solved], and remove the single section one-way bearing from the aluminum hub, using a sharp punch, dimple the area inside the hub where the bearing normally resides about 20 or 30 times, install red or better loc-tite, press the bearing back into the hub, be careful to insert correctly or the bearing will work in reverse [problem #3 solved]. These upgrades can be arranged through your local machine shop, some Whizzer dealers, or check in the vendor section for other options.
Because of the changes during production, it is impossible to expect all versions to react exactly the same, but It is very easy to like the way it works with the flat head Whizzer motor.
This post is not intended to discredit any company, person, persons, suppliers, or vendors in the USA or any foreign country, but as information to aid in adding longer life to some automatic clutches.
Have fun,
Quenton
