The clutches on a Diablo are made by Salsbury. I wrote Salsbury once looking for information and this is what they said:
Dear Bruce:
Thank you for your letter and the Service Bulletin. Salsbury Industries sold the torque converter line of its business in 1993. As such, there are no parts available as all items were transferred during the sale 15 years ago.
Best of luck to you.
Sincerely,
Michael L
SALSBURY INDUSTRIES
Los Angeles, CA 90001-1598
Oh well, it was worth a try.
The primary clutch is Salsbury series 700. This clutch is common on snowmobiles in the late 60’s and early 70’s. Salsbury made the same clutch for several applications by changing the tapered bore accordingly. Typical bores are 30mm or 25mm on the wide end of the bore. The Hirth 54R Special used in the Diablo 500 & 502 along with the Hirth 190R used in the Diablo 503 all have unusually small tapers on the motor. They are about 24mm on the wide end. The bore of the clutches is about 23.50mm at it’s widest point. This is what makes these clutches so special and rare.
If you blow up your clutch, you may be able to find another 700 series clutch and use parts from it to fit your own. Whatever you do, don’t break the stationary side of the clutch as that is the piece with the uniquely small taper.
Clutches from the factory have no threads in the bore. If you need to remove the clutch, you need to tap the bore of the clutch and then use a jacking bolt as shown. Any other method of removal almost guarantees damage to the clutch or crankshaft. The tap and puller are shown below. A impact wrench can be used to thread the clutch, just go slow and steady and keep the tap as straight as possible.
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How it works – The faster the clutch is spun, the more centrifugal force applied to the roller weights which move the clutch plate in closing the gap and grabbing the belt. If you were to watch it operate at high speed, you would see the belt move toward the outer edge of the Primary Clutch while at the same time, moving down into the Secondary Clutch. The clutch cover is a ramp plate and is also important to operation as the rollers roll against it forcing the inside belt plate to move. Guess that is why they call it a “Ramp Plate”.
These clutches are fairly hardy. Not much to go wrong with them. Common problems:
The faces get oxidized – Being very careful while the engine is running and having the belt removed, I span a piece of emery cloth across the face and it polishes up nicely. Do this at your own risk.
Ramp Plate screws bust off. Does your Primary Clutch have allen headed screws or hex headed bolts? If you have screws, those are original. If you have bolts, your clutch has been updated with a Service Bulletin. I suggest not to reuse the screws and replace them if you remove them. When you put them back in, the torque spec is 2 foot pounds or 24 inch pounds.
If you have screws and they are too tight to get out, you can cut a 3/8″ nut in half and place it over the screw head and weld it together. The heat will loosen the screw and the 3/8″ nut gives you something to grab on to. .
Clutch springs can break and the pins can get worn. Spring/pin kits are available.
Lubrication – I’m use a Comet Clutch Lubricant on the springs and rollers. Light oil or graphite would work too.
The Secondary Clutch is also a 700 Series.
These clutches are also fairly hardy, but if anything, the alignment pins come loose and that can be a problem. Looking at the above left picture, you can see the peened over rivet end of the spacer at 2:00 and 6:30. However, not the rivet at the 11:00 o’clock position. The rivet peen is coming apart and this rivet is loose. Pins can be replaced using shoulder bolts and once installed, cutting off the head.
To pull the clutch apart, push down the cup and remove the snap ring. If you don’t have a jig for this or another good technique, ask someone to push down the cup while you remove the snap ring. Otherwise it will pop off and hurt you.
Once apart, it can be easily cleaned up and lubricated.
If the clutch faces have cracks in them, best to locate a replacement. If the pins are loose or broken, they can be replaced with a shouldered bolt.
If you have a Secondary Clutch that is frozen on the gearbox shaft, that is a problem. I have tried spraying penetrating oil on them almost daily for 6 months and still could not get them to budge. Another enthusiast shared this method of using a 1/2″ plate in a press and it was successful getting a few clutches off that would have not come off any other way. On a few other clutches even with this method, I had to put some strong heat on the exposed clutch shaft (where the spring is) and they popped loose. However, this wrecks the spring.
Before cutting a clutch off, breaking it or wrecking springs and parts, be sure you have a replacement option. Better to know that before you break something that you cannot find a replacement for.
The original drive belt for all Diablos is a Bolens 180-1047. As this belt is no longer available and no current manufacturer makes a match for this belt available at retail outlets, Go Go Diablo contracts directly with Gates to reproduce the Trail Runner 6014 Snowmobile Belt.