Mk 3 sports chain size

[Ray Dodds]

Hi, Can anybody tell me the correct chain size i am getting a clanking from the front sprocket on take off i am suspecting its the chain worn but i dont want to buy the wrong one i have checked the links on the rear sprocket and can lift somewhat at the centre of the run i think that is the accepted method of checking for strech? or does any body have other ideas of my clanking noise, Regards Ray

[Doug]

Ray,

According to the spares book, the rear chain for all Mark series (excluding Plus and Comp. models) was 1/2 x .305, 116 links, standard sprockets of 19 and 60 teeth. For checking wear in the chain, the handbook states 3/4 inch up and down play midway between the front and rear sprockets, with the wheels on the ground (not on the center stand.) If you can pick the links off the rear sprocket, that is not a good sign! The clanking could be the chain slapping against something. If the chain were jumping the front sprocket (and I have seen a very worn front sprocket so know they can be run down right to nubbins!) you should be reporting a lurching sensation too as the drive was interrupted. Though unlikely, ditto if you were over-riding the shock absorber cam but more violently so. However either of these is indeed most likely when taking off and torque to the rear wheel is at the highest.

If you had said it clanked after you went over a bump I would suspect the center stand bouncing against the frame because the retaining clip is weak or missing.

-Doug

[eddie]

Ray,
        It is quite easy to check whether the final drive shock absorber is 'jumping'. Remove the cover and undo the centre nut (1/2" BSF), remove the end plate, spacer and spring. Slowly turn the rear wheel while holding the shock absorber cam in place by hand. When the cam rides over the top, the centre boss should be proud of the splined sleeve - if not, add a spacer washer to the boss of the cam. Reassemble, and fully tighten the centre nut - it should be tight, it is not there for adjustment. Road test to see if there is an improvement.
      Your problem of the drive jumping may have been caused by a mismatch of parts - Mr Douglas produced 2 lengths of splined sleeve, and over the years, the sleeve may have been replaced by the longer version.
                             Regards,
                                    Eddie.

[Ray Dodds]

Many Thanks Doug and Eddie i have checked the shock absorber thats good and as you sugest it is at the first movment of the chain that i get the klanking at about the right speed of the chain over the front sprocket so i am going to try a new chain the renold list has it as a 110046 is that corect Regards Ray

[Doug]

Ray,

Some Renold chain numbers and sizes covered here:

https://www.douglasmotorcycles.net/index.php?topic=1301.msg4515#msg4515

including 110046.

-Doug