The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Crossrodes on July 06, 2010, 07:08:15 PM
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I'm just in the process of disassembling the engine to remove the crank thrust washer and replace it on my '79. Since I've removed the timing chain (marked the sprocket) I've ordered a kit from Motobins.
My current chain looks OK and the guide looks good but the tensioner looks worn...but I'm replacing them anyway. What does look odd are the teeth on the crankshaft. The teeth on the camshaft sprocket have rounded tips whereas the teeth on the crank sprocket are almost pointed. My question is: Is this normal on a '79 or do I have to replace the crank sprocket too (assuming it it replaceable)?
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Pictures may be necessary to gauge whether they are sharp from wear, or were originally formed that way. It is common for the smaller of the (2) gears on any chain drive aparatus to wear faster than the larger one, but if the other doesn't look worn at all then I'd doubt that the sprocket wore itself out without showing wear on the other.
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I just took a look at the pictures of sprockets on the Motobins website and judging by what I see there I think my sprockets are OK. Thanks for the feedback.
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Mike,
Keep in mind the crankshaft sprocket has to have exactly half the teeth of those on the cam sprocket. The crank sprocket makes two revolutions for every one rev done by the camshaft gear. Simply put, the crank gear has double the mileage as does the cam gear. The smaller cam gear does have teeth that are a bit more "pointy" since they have to fit a certain number of teeth around a smaller circumference.
Really badly worn sprocket teeth may also have a slightly "hooked" appearance.
Wish I had a pair of new gears on hand for comparisons...
Monte