Clutch/primary drive/starter quandary

You have been following Beldrivemans numerous posts on other forums, ignore them and concentrate on setting up the bronze plate clutch by the book. I did this and no more slipping, on a mk3 you need 20/50 oil in the primary so the chain tensioner has a better chance of working.

There have been lots on this topic. But the outcome always remains the same. if you are refitting your sprag then use the correct amount of 20/50 oil. My Mk111 has 20/50 in the chain case I have no clutch slip and still have an intact sprag (for now)

And read and file Peter Strand's excellent post on improving the starter and sprag. Dynodave does an upgraded starter motor if you do not want to go the 4 pole conversion.

Well the bronze clutch works well when you adjust the stack height by the book, the diaphragm spring has a varying pressure which you can use to get it high when engaged and then lowering as you disengage, so your clutch will not slip and be 2 finger operated. You also need a good clutch cable, PTFE lined with stainless wire is best.

Having owned two 850 Commandos (Mk 1A and Mk 3)over the past 40 years I can reiteratethe above comments. Always used 20/50 oil in the primary up to the level screw ,andwith clutch adjustment maintained as per the manualthe clutch doesn't slip.Clutch operation can be made very light using a quality cable routed to give no abrupt bends. If clutch slip does develop after a large mileage, cleaning off the bronze plates and readjusting according to the book normally cures it - if slip continues theplatesprobably need replacing.

Alsohave always stayed with the standard triplex primary chain which has an extremely long life.

I can vouch for Andy the Chainmans products, I have one of the Merc duplex chains ready for my T120R and 2 of his pre-stretched cam chains for the 850 and the Combat. A quick comparison old to new shows how much better engineered they are.

Previously allan_walker wrote:

Thanks John and James.

Original-type bronze plates all in good order, and I have a new Venhill cable to fit.

I'll take care to set the stack height, because I've never had a light clutch with this bike (although my memories of my Mk2A bought new suggest that a light clutch is possible!)

James, dare I ask how your sprag fared on 20/50? Also the primary tensioner?

It's interesting to hear that you (James) recommend topping-up to the level screw. I've seen lots of info (disinfo?) on other forums that suggest the measured quantity of oil recommended in the manual brings the level considerably below the level plug.

The sprag and tensioner need all the oil they can get, so I'll go with your recommendation.

I've no desire to change from a chain primary drive. Too much expense on top of what I've spent so far. If the chain has tight spots, I may replace it with one of the Mercedes duplex chains supplied by Andy the Chainman.

Never had a problem with the sprag but then again I never used the electric starter as my Mk 3 always started easily on the kickstart - both when it had the original points ignition and after fitting Boyer.

Filling primary chaincase with 20/50to the level screw has neverbrought upany obvious problem.As a matter of routine , whenever I had the primary cover off I'd always take outclutch plates and give them a good cleanwith petrol before readjusting as per manual.

Regarding heavy or light clutch lever action, also check the clutch actuating lever that the cable pulls on. It only needs to wear a small flat to change the lift ratio as it pushes on the roller.

Norm.

With the latest bronze friction plates, there is only a thin strip of bronze around the outer edge of the plate. This means that there is a huge amount of steel plate not doing anything but adding weight. I put my steel plates on the lathe and removed a broad ring of steel that was not doing anything other than wearing out the gearbox mainshaft bearing. I'm also toying with drilling some holes in the friction plates inboard of the friction material in an effort to reduce weight.