Author Topic: Metal shavings in oil  (Read 1076 times)

Offline berger

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Re: Metal shavings in oil
« Reply #30 on: 26.07. 2019 13:27 »
Owain this is the offending item that never seized but the result of glaze busting the bore with an excited honing person. the other bore deglazing was ok and so was the piston but this one tormented me with clanging about for over a year.

Online chaterlea25

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Re: Metal shavings in oil
« Reply #31 on: 27.07. 2019 00:13 »
Hi Owain,
I would go for new pistons
With a sidecar attached I would go for 0.005in. clearance
Theres nothing wrong with the modern pistons even though some had dodgy rings but I think this problem has been sorted
Make sure the carb is sorted before you go for any long runs, and start off with short trips and keep checking the plug colour
Make doubly sure the ignition timing is as near perfect as possible and the same on both cylinders

John
1961 Super Rocket
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Online RDfella

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Re: Metal shavings in oil
« Reply #32 on: 27.07. 2019 20:39 »
Nowadays things aren’t as simple as they were. We know what the bore size should be, and manufactures make pistons to achieve the correct clearance. BSA etc will also specify what the clearance should be. But what we don’t know is whether modern pistons are metallurgically similar. Do they have the same coefficient of expansion as originals? If they expand more, we’ll need greater clearance, but how much is anyone’s guess. Whilst I wouldn’t recommend it for road use, but I always used to bore motorcycles that were to be raced .003” over recommended size. Same for a certain make of turbo marine diesel that came through my workshop frequently in the 70’s. The latter were almost guaranteed to seize at standard spec. and at ten grand a piece .003 was cheap insurance. Actually .005” over standard was needed for the hotter version of that engine (causing lots of blow-by when cold). Those uprated engines really needed oil-cooled pistons.
Getting back to the BSA – the oil pump will need to be stripped and checked – I’d be amazed if the teeth didn’t show signs of pumping debris. And make sure the ignition isn’t retarded, as that causes overheating.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online ironhead

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Re: Metal shavings in oil
« Reply #33 on: 27.07. 2019 23:17 »
I'll post some more pictures of the pistons after lunch.

HI Owain.
 Have you fished lunch yet? *razz* Could you post some pictures of the uncleaned piston from all sides.
Score marks in different places tell stories.
SA

Offline owain

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Re: Metal shavings in oil
« Reply #34 on: 30.07. 2019 09:06 »
Thanks for the tips RDfella, I'll be sure to strip down the pump for an inspection and clean. Fortunately I have a spare pump laying around somewhere as well, which might be usable for parts if the pump is showing signs of wear.

Sorry about the delay with the pictures, I've attached some more pics of the pistons now. I've cleaned one up and left the other one as I found it (new pistons are on their way!).

I've also cleaned the sludge trap but I was a bit heavy handed when wrapping the new sludge trap plug (plus I wrapped directly on the threads, rather than either on the crank or plug itself). I wish I did a cleaner job and it'll be a bugger to remove during the next strip down, then again I wanted to be sure that the plug was totally secure :/
Sweden & North Wales
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Online Greybeard

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Re: Metal shavings in oil
« Reply #35 on: 30.07. 2019 09:32 »
I've also cleaned the sludge trap but I was a bit heavy handed when wrapping the new sludge trap plug (plus I wrapped directly on the threads, rather than either on the crank or plug itself). I wish I did a cleaner job and it'll be a bugger to remove during the next strip down, then again I wanted to be sure that the plug was totally secure :/
Bit confused about the word 'wrapped'. I don't think you have wrapped the thread with plumbers tape. Are you are talking about using a centre punch to lock the thread?

Offline owain

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Re: Metal shavings in oil
« Reply #36 on: 30.07. 2019 11:17 »
Maybe it's a term I've made up. I always thought people would say to 'wrap' the thread? haha using a center punch to lock the thread is what I mean though.
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Online ironhead

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Re: Metal shavings in oil
« Reply #37 on: 30.07. 2019 11:37 »
Thanks for the tips RDfella, I'll be sure to strip down the pump for an inspection and clean. Fortunately I have a spare pump laying around somewhere as well, which might be usable for parts if the pump is showing signs of wear.

Sorry about the delay with the pictures, I've attached some more pics of the pistons now. I've cleaned one up and left the other one as I found it (new pistons are on their way!).

I've also cleaned the sludge trap but I was a bit heavy handed when wrapping the new sludge trap plug (plus I wrapped directly on the threads, rather than either on the crank or plug itself). I wish I did a cleaner job and it'll be a bugger to remove during the next strip down, then again I wanted to be sure that the plug was totally secure :/


Hi Owain,
Looks like tight bores as the others have suggested.  Heavy scoring on the side of the piston & not much or none on the skirts usually means a bent rod or bore mis alignment but yours look like heavy scoring all over. *eek*
SA

Online RDfella

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Re: Metal shavings in oil
« Reply #38 on: 30.07. 2019 12:05 »
Heavy scoring? That's moderate to light. See pic below for heavy scoring. Note too over 1/2 inch has melted off the piston crown (which then went out the exhaust to weld up the turbocharger)..
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline Swarfcut

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Re: Metal shavings in oil
« Reply #39 on: 30.07. 2019 12:34 »
RD  Nice one for the great mechanical disaster album.

 Owain. Are your new pistons another oversize?  The machinist you used may have bored and honed to published figures, and assumed the pistons were smack on for dimension. They may have been not quite right and it is always best to double check by measuring the piston, allowing a clearance and boring to that. In effect the freshly bored cylinder is like a big nut, only at the correct bore at the bottom of the " thread ".  Honing attempts to make the sharp peaks of the thread into a plateau, and is done with various methods, not all ideal, such as...fixed stones in a rotating carrier, adjustable for fine increases in cut, stones on a three legged carrier, pressed onto the bore by centrifugal force, and abrasive balls  bonded onto what looks like a sweep's  flue brush. Some of these are more suited to breaking the glaze, rather than accurately honing to a finished size.

  Ask to see the hone....you need them to use one that has some form of incremental adjustment if you are going to use your new pistons in that old bore. The existing bore needs accurately sizing to the new pistons give an adequate running clearance.

 Don't just dump the old pistons...They have some value.

 Swarfy.

 

Offline muskrat

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Re: Metal shavings in oil
« Reply #40 on: 30.07. 2019 21:25 »
 Don't just dump the old pistons...They have some value.

 Swarfy.


Yes I cut'em in half and make trophy's for the bike show.
Cheers
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Online morris

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Re: Metal shavings in oil
« Reply #41 on: 30.07. 2019 21:36 »
Don't just dump the old pistons...They have some value.
 Swarfy.


Yes I cut'em in half and make trophy's for the bike show.
Cheers
Cut them in half horizontally at the height of the gudgeon pin hole . Upside down they make a nice little ashtray...  *smile*
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Online RDfella

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Re: Metal shavings in oil
« Reply #42 on: 30.07. 2019 21:40 »
Not if they're 10:1 morris ..........
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Online duTch

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Re: Metal shavings in oil
« Reply #43 on: 30.07. 2019 22:34 »

 
Quote
Maybe it's a term I've made up. I always thought people would say to 'wrap' the thread? .......

 Maybe they meant 'rap' ?  *conf2*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
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Offline Minto

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Re: Metal shavings in oil
« Reply #44 on: 31.07. 2019 02:20 »
Don't just dump the old pistons...They have some value.

 Swarfy.


Yes I cut'em in half and make trophy's for the bike show.
Cheers

Muskrat
What do I need to do to win one of those, they’re lush!
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