Clutch

For primary chain, chaincases, clutch domes and covers click here; for cables and cable adjusters click here. See the notes (click here) if trouble is experienced with the clutch rubbing on the chaincase on swinging arm machines. The clutch fitted to all Ariel models, like the gearbox, is made by Burman, 3 designs being fitted over the years, all listed as ‘dry’, although they will run in oil. Similar but different clutches are used on the R, T and H gearboxes fitted to the Colts, we can help with a few parts for these, please ask.
1926-32 as fitted to the ‘Q’ gearboxes and fitted to most models, the exception being the few models fitted with Sturmey Archer gearboxes and the Colts. Large diameter plates, 5 springs, rubber cush drive and 1/4” x 15/64” rollers, mounts directly to a taper on the gearbox mainshaft, push rod adjustment in the pressure plate.
1931-35 as fitted to all models with CP and BA gearboxes. Same design as the ‘Q’ clutch but using smaller diameter plates and only 4 springs, push rod adjustment in the pressure plate.
1936-58 fitted to all models and unique to Ariel. The bearing is now made of loose needle rollers in a brass cage and the large diameter plates fitted, 5 springs again but no cush drive. On the CP and BA gearboxes the clutch is mounted on a shoulder of the shaft that prevents replacement of the gearbox sprocket without dismantling the gearbox but this becomes a loose adapter on the GB gearboxes. All models have 3 friction plates except the civilian 350cc that has 2. To counteract the tendency for the internal mounting splines of the centre to wear the length was increased in 1948 by forming a boss in the centre of the centre! In 1957 the tags at the rear of the centre were removed allowing the plates to fall off the back, the addition of friction lining on the basket prevented them going too far and increased the friction surface. The centre nut started out as a reasonable size with a thick washer for support but was changed in 1950 for one with a huge hexagon and a lock washer; the more convenient earlier version can be fitted if preferred. Adjustment of the push rod free play is made at the kickstart end of the gearbox.
All these clutches are good designs and work well providing they are in good condition. Most problems are down to missing thrust washers, worn splines and distorted plain plates, which must be flat. Problems in use are usually confined to the centre nut becoming loose and the 6 set pins trying to work their way through the centre.Burman introduced alterations at the start of the calendar year and not in September so there is usually some overlap between the years, the most noticeable being the introduction of the GB gearbox in January 1952, some 3-4 months into the 1952 model year, that started in September 1951.

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