SOHC.co.uk Forums > CB750
Points Cover Oil Leak
SeanFD:
I have a considerable leak from my points cover - CB750 K2/4.
Having read related posts it seems the issue is either the crankshaft seal or the o-ring on the advancer shaft or both.
O-ring replacement is relatively easy, but there is debate as to whether the seal, which has an outer lip, can be replaced without splitting the cases.
Now FASTURD posted on the US site on his similar experience a while back and concluded with this:
http://forums.sohc4.net/index.php/topic,71635.msg868522.html#msg868522 - Go down to post No 22.
Having just replaced the head gasket, I do not want to take the engine out again, so I am going to try to check where the leak is coming from and then if necessary try to replace the seal with a non-lipped one as described above.
I can get a seal with the correct dimensions, one single-lipped and the other with two lips - internal I think. The second lip is I believe a dust seal.
https://simplybearings.co.uk/shop/advanced_search_result.php?search_in_description=1&keywords1=30&keywords2=42&keywords3=8&
Does it matter which one I use and if so which one should I go for?
McCabe-Thiele (Ted):
If it was me I would go for the double lip if it's no thicker in depth.
Others here will have an experienced view.
Skoti:
I think it's an engine out and split the cases job to renew that oil seal.
I'm sure the oil seal has outer ridge that locates into grooves on the cases, but somebody else will be along shortly to confirm or correct me on that.
But you won't have to touch the top end to change that seal, just pull off the side casings and remove all the gubbins, then turn the engine upside down and spilt the cases, remove the cam chain tensioner so you can ease the crank up a bit to remove the seal.
Any way good luck with that.
Skoti
K2-K6:
Some time ago (at least a year or two) we discussed exactly this but can't find the thread immediately.
After much debate, the upshot was that it wasn't that difficult to change it successfully in situ from what I recall. Memory says it was someone in Australia that was doing it or referenced something from there.
More searching may find it, obviously ;D but I can't with logical search phrases seem to locate it.
McCabe-Thiele (Ted):
--- Quote from: Skoti on September 20, 2022, 10:54:01 AM ---I think it's an engine out and split the cases job to renew that oil seal.
I'm sure the oil seal has outer ridge that locates into grooves on the cases, but somebody else will be along shortly to confirm or correct me on that.
But you won't have to touch the top end to change that seal, just pull off the side casings and remove all the gubbins, then turn the engine upside down and spilt the cases, remove the cam chain tensioner so you can ease the crank up a bit to remove the seal.
Any way good luck with that.
Skoti
--- End quote ---
I think that is only the case if you use an original seal the link appears to show a replacement that worked without splitting the crankcases.
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