I tried both types of sprocket on an engine I have on the bench and found they both have float on the crank, however when I put the retaining bracket on and tightened it up the sprocket (the one with the recessed teeth it locked solid to the case). Greg I think you should try the same thing, it won't explain the wear on the clutch but would on the case, its a puzzle this one.
Al.
Rebuilt engine seized
Hi Greg, my evil twin in UK could be on the right track I reckon. I looked at the pictures again and you have the raised type sprocket which, I think, should go with the shorter type retainer. Maybe you used the longer retainer on the build and it caused the sprocket to "cock over" and caused the damage to both sides. I also have an engine on the bench so I'll take a look at it tomorrow. I'll be taking a look at my other built up engines today and let you know what I find.
Cheers, Brian.
Hi Greg, I checked four of the engines and they are all OK, so I went to the engine I am currently building and started taking readings with the two different sprockets. That didn't reveal much apart from the fact that there is more clearance between the rotor face and sprocket on the flat faced type. (0.060" compared to 0.020" on the raised sprocket).
My conclusion is that as long as the radial play on your sprocket is not excessive, then use the correct "stopper" for that sprocket. ie. Short for the raised type and long for the flat type. I reckon we tend to overthink things sometimes. By the way Graham, back to basics is always good. Nice pickup on the barrel flatness. There we were overthinking again! Cheers, Brian.
Thanks Brian/Al
I did have the newer sprocket fitted with the older keeper so almost certainly this was why the sprocket was rubbing on the cases. What I am not quite sure about is whether the new sprocket is compatible with the older rotor, my testing suggests not but I am getting an old sprocket to check with the old rotor to be sure there is not an individual problem with my old rotor. Greg
Looks like you might have it sorted out Greg. As Al pointed out, just a bit of axial play on the sprocket with the rotor and sprocket installed is what you are aiming for, then install the correct keeper.
Regarding the oil seal installation into the case and whether you use sealant. People will disagree with me but I always put a very thin layer of silicon sealant around the seals when I install them and have never had an issue. The point is to use very little and it make sure that it's not going to get into any oilways. Check that the seals have not moved when the cases are tightened up. Cheers,Brian.
Brian/all
I now have an older flat faced sprocket and this looks fine with the older rotor and the correct keeper. I get the same measurements as you in that the total width is the same but the older flat faced sprocket has a deeper shoulder for the sprag clutch to work on which keeps clearance between the back of the clutch and the sprocket. The only difference is that I did not measure any clearance when using the newer ridged sprocket and the older rotor ( though this was measured off the engine with no keeper in place). So to conclude I think you need either the older sprocket, older rotor and older keeper or the newer ridged sprocket, newer keeper and cb72(L) rotor and any mix between the 2 sets could cause problems. I had the worst possible combination of old keeper and rotor with new sprocket! Ps I think there might be a third version of the sprocket, that is the early one with a plain brine bush rather than a groves one but dimensionally this will be an ‘early sprocket’. So time to put it together again.... Greg Greg
Good investigation and useful to all of us who build bikes from odd parts... G
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F
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