Cam buckets

blab

blab

Hero member
Location
Adelaide South Australia
Can anyone enlighten me ( maybe with a picture) as to what is acceptable wear on the outside of cam buckets.Between bucket and head.
Mine have quite a bit of wear, perhaps this is normal. I thought the head would wear, not the bucket.
Also what causes the cam to show wear and blueing between the bum and lobe.
 
Shouldn't really be able to see wear on buckets - needs measuring (or experienced feel!). Blueing on the cam lobe suggests inadequate lubrication -> overheating....maybe that has also affected bucket(s)?  Couple of pages from 1000/1200 workshop manual may be of interest.
 

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Rub the top of a bucket lightly on a flat surface of 400 wet & dry.  High/low spots imediately show up.  Using overly worn buckets might well damage the cam lobes in the long run.  Shouldn't be able to detect wear ridges by running a thumbnail across the surface.  Circular ridges form first, then crack-like lines from the centre... high time for the scrap bin. :D

Blueing is definitely a sign of over-heating.  Check if oil exits from ALL cam bearings when engine is cranked.  Excessive application of gasket goo somewhere on the cylinder base or head surface can block the oil travelling up the stud bores.

I like the statement "should be in perfect condition".  As if this were a perfect world! ::)

piet
 
Wear on side sides of the buckets means IMHO that the buckets aren't turning. It's a fact that the buckets are, or shouldn't have a flat top surface, if they do the buckets will just bounce up and down. But when they have a slight dome they turn slightly as the lobe runs over the top surface of the bucket. Therefore spreading the wear evenly.

:o Man, it almost sounds like I know what I'm talking about!
 
dja982 said:
Mmmmmmmm I think you might just have made that up.
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Mmmmm, don't think so. I'm not saying they spin at a rate of knots, just that they turn slightly. Pull the cover off, make a mark on one, run motor for a bit and check mark position. Then clean up the oil mess  :D
 
chrisk said:
Wear on side sides of the buckets means IMHO that the buckets aren't turning. It's a fact that the buckets are, or shouldn't have a flat top surface, if they do the buckets will just bounce up and down. But when they have a slight dome they turn slightly as the lobe runs over the top surface of the bucket. Therefore spreading the wear evenly.

:o Man, it almost sounds like I know what I'm talking about!
Click to expand...

Theoretically, that's correct.

From an engineering pov, it is easier to make the buckets dead flat and grind the cam lobes at a very slight angle, which forces the buckets to rotate as the cams spin.

High-mileage Laverda buckets are rarely even close to dead flat.  Usually, dished, circular wear patterns are found.  Cam lobes will most probably no longer be angled at this point either, normal wear and tear taking its toll.  Add excessive/inadequate clearance, you may find signs of hammering or siezing.

Another method of rotating buckets is to have the lobes acting on them off-centre.  This works even when both components are worn.

Buckets are available in several over sizes.  Head requires careful setting up to machine the bores to size.

piet
 
chrisk said:
Oh, and if lobes are getting that hot that they blue, then you ain't got enough oil to allow the bucket to turn. Catch 22 I'd say.
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Blued cam lobes/buckets?? :o :o :o Can't imagine that's a good sign or has long to go... :o :o
 
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