Dished buckets. 180 Jota

TheWrongTrousers

TheWrongTrousers

Senior member
Location
South London
Well, its time to adjust my valve clearances. Been a while, I must admit. So it seems as if two of my buckets ( both exhaust and intake on middle cylinder) are a bit dished on the top and will need to be replaced. The other four buckets are showing signs of wear but not too bad I would say. The cam shafts both look in good condition considering the bike has done 50,000 miles or so.

I wonder why it is that this has happened on my middle cylinder only. It could be a co-incidence but then again this might point to something more worrying. It's all swimming in oil up there, or so it seems anyway.

Any thoughts anyone ?

I don't suppose anyone in the UK has any buckets they are willing to part with for a fair price ?
 
Three possibilities: heat, inferior bucket metallurgy and/or lack of bucket rotation. Do you see a circle pattern on the bucket face indicating rotation? How far out is the valve lash on the center cylinders vs last adjustment?
 
Just been through this whole journey whilst recommissioning 1981 Jota #7606. 3 different size buckets, hard to get. I got a set from Wolfgang. Dam laverda and Redax none in stock.
Thinks to check:
Oil pressure coming out of pump
Oil flow through oil cooler
Oil flow to Cam blocks
Cam blocks fitted right way around
Buckets not seizing in bores
Buckets not bottoming out

Went to lots of trouble to build equipment to test flow, and have a special hose made for an oil pressure gauge adapter. Worth it for peace of mind
 
perhaps, in the past, the top face of the TAPPET has been ground down to gain the vital valve clearance and this his caused the thickness to go below a safe and stable dimension.

I did it in the past as a stopgap, but it didn't run like that for vary long, due to another failure elsewhere. Funny thing is, when I did it, I thought that the offender would "bow" out, not in!
CLEM
 
Here they are. Picture worth a thousand words. You don't really get an impression of the dish effect from the photos taken from above. Hopefully the pictures will give an impression of the wear pattern on my buckets. The dishing is on both buckets on middle (2) cylinder. The others are worn in varying degrees but not concave in any way.
 

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You say 1+3 not too bad - all comprehensively mullered, I'd say!  Reckon your cam lobes will be showing signs of distress too? In addition to previous suggestions, poor quality/contaminated oil and/or changes ignored?

4C cams give the valve train a hard life, but wouldn't expect to see that even at 50,000 miles.

OCT stock buckets.
 
Fair comment Rob, and I can see how looking at the photo's one might think that a lack of oil changes/poor oil is the culprit. But I have always been pretty good with the oil changes and have never used cheapo oil, so I would be a bit surprised if that were the cause.
 
laverdas said:
Clearance to small and pinking that will act like a ballpein hammer 🛠 on your bucket.
Regards Andy
Click to expand...
the reason for the above quote is it happened to me but i just kept riding and in the end I did three valves buckets, three valves and the cams.
The bike started pinking going over the high alps and i should have stopped and done something about it but that's another story.
Regards Andy
 
I have always been pretty good with the oil changes and have never used cheapo oil,
Click to expand...
OK - just a thought.  So back to the other possibilities then. 

Some light marking is to be expected - a circular pattern shows bucket is rotating as it should. Something like this
1615088_orig.jpg


And this is what happens when clearance disappears
 

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Hmm, yes i see.  My gut feeling is that I may have caught this in time and perhaps with some new buckets, all will be well. The bike never pinks if I use good fuel and it generally starts on the button, runs really well and fuel consumption is not high. Plugs a reasonable colour.

Andy, you were very unlucky. Not a lot you can do about things in the high alps. Keeping going probably seemed like an option at the time.
 
All tappets (:D) are knackered and not fit for re-use (well, I wouldn't...).

I'd check the cam lobes for damage as well, seems the engine has run a long time with incorrect valve clearances.  Might well be signs of rounding off at the lobe tip.

I have a limited number of NOS tappets in stock, these are of the later, shorter, thinner-walled and therefore lighter type.  I also have a few re-conditioned originals, these have had a very slight skim to the tappet top surface.

Drop me a line via PM if interested.

piet
 
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