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Re: Engine shock absorber

It's interesting that they show part no.116 in the wrong position on the exploded drawing...It fitted onto the crank first, followed by part no.56 etc....

The spacer itself is approx. 1/4" thick and should have some clearance between its outside diameter and the crank cases...

The exact thickness of the spacer can be deduced when the engine sprocket and clutch sprocket are in alignment...Ian

email (option): ian@wright52.plus.com

Re: Engine shock absorber

The one on my B33 was 12mm thick.

Re: Engine shock absorber

I don't see the locking washer in Peter's photo which sits in the splines and which once you have tightened the nut you fold back into the recess of the nut to stop the whole plot undoing itself which if not done can then gives rise to the sprocket riding over and eliminating any drive to the clutch. It also gives rise to the nut punching its way through the outer chain case.

As a point of interest there are 2 lobe and 4 lobe engine sprockets together with the corresponding other part i.e. 2 lobe or 4 lobe. There will of course be a reason for this but I am not aware of it - Ian will no doubt advise. Thanks.

Re: Engine shock absorber

I never fit the fiddly lock washer #59. I use Loctite. Ron

email (option): ronpier@talk21.com

Re: Engine shock absorber

As a matter of interest, has the nut ever been known to put a hole in the outer chaincase? I'd have thought that drive would've been lost well before the nut got to that position.

Re: Engine shock absorber

The drive is lost when the nut comes undone, but the engine still keeps going and I've seen serious damage to the cup in the chain-case. Ron

email (option): ronpier@talk21.com

Re: Engine shock absorber

Ron Pier
The drive is lost when the nut comes undone, but the engine still keeps going and I've seen serious damage to the cup in the chain-case. Ron
Yes indeed one of the M.20s I had in the early 1970s managed to seriously damage the outer chaincase when the nut came undone. As Ron says the engine keeps running but all drive is lost and the nut will rub against the inside of the outer chaincase and punch a hole through it.

As a matter of interest I tried to get the damage repaired by brazing the damaged area of the chaincases. The guy that did it said the metal was very poor quality and that without the paint it was in fact porous.

Re: Engine shock absorber

Yes mine had been badly damaged it it's past life and repaired with thick body filler. Ian gave me a knackered post war cover, from which I removed the cup and I got it TIG welded into my own cover. Ron

email (option): ronpier@talk21.com

Re: Engine shock absorber

We all know that the main nut has to be done up tight, but back to the spacer at the inside of the splined shocker carrier. Some have this spacer built into the carrier some don't as the one in this thread. At least without one you can fine tune the primary chain line, i make a wide spacer and trim it to size by using a steel rule across the sprockets to get them in line. Good thing is the new spacer does not need to be hardened as if the shocker nut is done up tight this spacer should never move. If the shocker nut is run loose this spacer along with the large spacer between the 2 main drive side bearings will wear and reduce their thickness bringing the main bearings closer together and the primary chain will be out of line.

Re: Engine shock absorber

The 2 lobe sprockets,cam and spring were introduced on later post war models...Springs for the 4 lobe set up were wound from flat wire and from round wire for the 2 lobe set up...The pressure exerted by the two spring types is quite different so parts should not be mixed...The spring nut also differs slightly...
The 4 lobe cams are quite pointed and do not move against each other readily when force is applied to them, so a lighter spring was used for these...The 2 lobe cam had far larger radii and was altered to smooth out the cam action...As a result the cams move against each other more easily, so a heavier spring was used for these to compensate for that...
As a point of interest there are two versions of the 4 lobe cam...Later 4 lobe cams had the width of the faces of the cams increased to reduce wear...

Engine sprocket carriers with the spacer machined as part of the carrier have the advantage that if the nut does come loose they are not subject to resulting wear as the whole carrier is hardened...If I make spacers up for the 'separate' spacer types I make them from silver steel and harden them....The main bearing spacer within the crank case is also better for being hardened IMO as that removes the potential for wear in the case of a loose nut...

When the 'one piece' sprocket carrier is fitted chain alignment is adjusted (if required) by the use of spacer shims..These are .005" and .010" thick....Part numbers for these shims are 66-1707 and 66-1708...Ian

email (option): ian@wright52.plus.com

Re: Engine shock absorber

Thanks for the replies about the nut punching a hole. I'd have thought that when the drive's lost due to the nut loosening & the vehicle comes to a clanking stop an operator would turn the bloody engine off? I can see of course that if the engine is kept running the nut will unscrew to the point of damaging the case. I suppose strange things happen to old motorbikes over their lifetimes.

Re: Engine shock absorber

A correction to my earlier post...The alignment washers 66-1707 and 66-1708 are .032" and .064" respectively...Not the figures I originally quoted...
Additionally, whilst on the subject, the 'flat wire' shock absorber spring used with the 4 lobe set up that was standard on all WD models should be 1 5/8" long when new and is considered not fit for further use at 1 15/32" long or less..

Another useful tip...If there is enough thread exposed when the crank shaft shock absorber nut is fully tightened a spare big end crank pin nut can be fitted as a locknut....Ian

email (option): ian@wright52.plus.com

Re: Engine shock absorber

Thanks guys for help. To sum up I need either 66-1707 or 66-1708 to make proper alignment plus part #116. What are its dimensions to make it or what is the part number to buy it?

email (option): petroucios@gmail.com

Re: Engine shock absorber

The part number of the spacer is 65-2540...Draganfly Motorcycles are probably the best bet as a source...Ian

email (option): ian@wright52.plus.com

Re: Engine shock absorber?

The most serious consequnce of the nut undoing is potentially to the crankshaft and flywheel. If the nut loosens the drive will slip but might still "get you home". When stripped for repair there may be play like main bearing wear on the shaft. Turns out the shaft is now loose in the flywheel as the rivets holding the two together have lost their grip because the whole assembly has rattled about. I found this out the hard way in an earlier life as a teenager. Since then I 've used the lockwasher AND Loctite and made sure the nut is very tight.

email (option): jb25@gmai!.com

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