Engine sprocket wear

[Phil C]

I've always got a question, as you'll have noticed.

Attached are photos of my (1965 B40F) engine sprocket. It looks, would you agree, like the RH side is more worn than the other? I've just bought a new chainwheel and a new primary chain, but before fitting them I'm just wondering if the engine sprocket wear is evidence of some misalignment. You'll also see there are signs of a bit of wear and tear here and there, eg on the crests of some of the teeth. Any advice, please? (This is new ground for me.) 

Thanks very much.  Phil

[Phil C]

By the way, when I say RH side I do of course mean the inboard side (just noticed the photos are not all the same way round, sorry.)  Phil.

[Phil C]

Further to my previous posts on this, a bit more information: I see that the crankshaft oil seal is running on what I believe is a spacer, marked "C", which I think (having read Rupert Ratio) is the thickest of three available (back in the day) spacers (sorry photo is a bit dark.) I'm not sure whether the wear on the sprocket suggests that's too thick or too thin. And of course I don't know when the wear occurred, before or after the spacer was fitted. Phil

[Phil C]

By the way, when I say RH side I do of course mean the inboard side (just noticed the photos are not all the same way round, sorry.)  Phil.

Sorry, I meant outboard, the side with the boss.

[Phil C]

Anyway, I'll see what the alignment looks like with a straight edge (steel rule.)

[Phil C]

Putting a six inch rule across the engine sprocket and the chainwheel, they look well aligned if the rule is below the teeth on the sprocket. Of course that's not the case if I try to line up with the rule on the actual teeth of the sprocket, because of the wear on the teeth. Except for the wear I think there's pretty good alignment. Do I need a new engine sprocket?  Phil

[DAVE BRADY]

Hi Phil,

As you have new clutch drum and primary chain you may as well go for the full set.  The worn front sprocket will cause the chain to wear a bit more quickly and in turn this will wear your new clutch drum a bit more quickly.  Also, for the sake of few more £s get some new clutch bearing rollers.

Dave.

[Phil C]

I'm happy to do that but do you think having a new engine sprocket will mean the "C" spacer is no longer the right one and the alignment is out?  Phil

[idie]

If the wear is the side the spacer is, then I would say that the spacer is to thick pushing the sprocket over.

[Phil C]

No the wear is on the outboard side, furthest from the spacer.

[Phil C]

I'm happy to do that but do you think having a new engine sprocket will mean the "C" spacer is no longer the right one and the alignment is out?  Phil

Anyone?

[idie]

I still think the spacer is to thick.

[DAVE BRADY]

Hi,

I would put the clutch drum and front sprocket on with the spacer that you have and see how much out it is.  Lining up below the teeth is probably more reliable and it needs to be as perfect as you can get it.  The difference between the spacers will only be in several thou.  It looks like you may need the slightly thinner one to take the sprocket in a bit.
Also, use a longer straight edge so that fully engages on both sprockets.  The back of a hack saw blade is quite good and measure any gap that you see.
What does RR say about this?

Dave.

[Phil C]

RR (vol 1, p.119) says use a 12" rule to check the outer edges are perfectly in line. (The illustration shows a 6" rule, but anyway whatever.) RR goes on to say if they're not perfectly in line then attend to the spacer by fitting a thinner one or shimming. He also says that if the crankshaft oil seal is fitted then removal of the spacer is very difficult. Anyway, I'll order a new sprocket tomorrow (and roller bearings) and hope the alignment is spot on because I don't know how to get the spacer out.  I'll let you know.  Thanks again.  Phil

[DAVE BRADY]

Hi, 

Have you got a couple of strong magnets?  If so you may be able to tease the spacer out.

Dave.