Author Topic: Metal shavings in oil  (Read 984 times)

Offline owain

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Re: Metal shavings in oil
« Reply #15 on: 25.07. 2019 12:36 »
Update: I've removed the engine and split the crankcases (at least, managed to remove the drive-side as I haven't managed to take the sprocket off timing side yet...).

I pulled the roller bearing off the drive side and the suspected shim was intact...but look at the state of these brand new pistons! (see attachment). As I mentioned the motorcycle has done less than 200 miles. Surely, this is not pistons should look like whilst running in the motorcycle?? I should also mention that during the first 100 miles, I had a few partial engine seizures whilst riding on the motorway. Although, could the huge amount crank end-float (0.021") have caused this amount of piston wear? 0.021". Irregardless, the bores on the cylinder don't look too bad (can't feel any scoring when running my finger nail down the cylinders) or maybe I'm letting my optimism blind me...Reckon the pistons are salvageable?
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Offline bikerbob

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Re: Metal shavings in oil
« Reply #16 on: 25.07. 2019 13:51 »
Your end float is about 10 times what it should be also with pistons like that I would checking to see if the bores were bored to the correct tolerances seeing as you say you  experienced what you suspect was partial seizures whilst running in.

Offline coater87

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Re: Metal shavings in oil
« Reply #17 on: 25.07. 2019 16:16 »
 I am taking it that "motorway" means 70 mph? Like our interstates? *eek*

 I think your break in procedure might be on the quick side.

 
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Offline Swarfcut

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Re: Metal shavings in oil
« Reply #18 on: 25.07. 2019 17:53 »
Forget the endfloat for now, go down to your reconditioner and ask him to give the bores a light hone. The bore is a shade too tight, the pistons need a light "polish" but should be OK to try again before spending on another set. Bear in mind  air cooled engines need a bit more TLC in the break in/running in period. Suggested bore clearance measured from the piston are listed in the BSA Service Sheet 701. For your engine 3 to 5 thou at the bottom of the piston skirt is the published figure.

 Swarfy.

Online Triton Thrasher

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Re: Metal shavings in oil
« Reply #19 on: 25.07. 2019 18:19 »
The bore that caused that needs a bloody heavy hone, rather than a light one.

Offline owain

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Re: Metal shavings in oil
« Reply #20 on: 25.07. 2019 19:02 »
I think you're right that I was a bit rough on it breaking it in, Although I still experienced partial engine seizures whilst riding on the back roads in N.Wales. 

I took the pistons and the cylinders to a machinist this afternoon. They said it was difficult to tell with the amount of scoring on the pistons but found it to be around the ballpark of 0.003". They too said that the pistons were 'usable' but advised me to get a new pair and to come back for them to remeasure and hone the cylinders to the correct size.

Also removed the sludge trap. An absolute mission but it appeared to be pretty clean inside. I'm not hugely keen to be spending another £100 on a set of pistons though. Then again, these ones do have a decent amount of scoring all the way round and I don't fancy knackering my cylinders (even if the next rebore would entail sleeving the cylinders).

It is also possible that my motorcycle was running too lean and getting too hot I suppose? Then again the pervious machinist was kind enough to join the crankcases together without me asking and without considering the end-float tolerances, so I'm too impressed tbh.

Either way, this seems like peanuts compared to those ignition problems that were plaguing me for months!  *beer*
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Offline Swarfcut

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Re: Metal shavings in oil
« Reply #21 on: 25.07. 2019 19:27 »
Owain.... Advised to get a new pair!!!!! Yes, 'cos they are in the business of selling pistons!  OK, a "reasonable/heavy" hone  (Thanks TT) may be more appropriate, but you will not damage the bore further. Try those pistons again, but do your research as to bore clearance....those folks do not realise what is involved and the reason for your problems...... Ignorance  of published data.

 Swarfy.

Offline RDfella

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Re: Metal shavings in oil
« Reply #22 on: 25.07. 2019 20:38 »
As an experienced engine builder, I wouldn't even consider using those pistons. If none were available it might - as a bit of a bodge - be possible to linish them, but then you're going to have excessive clearance = piston slap & oil consumption. They have seized. They're toast I'm afraid.
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Offline Swarfcut

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Re: Metal shavings in oil
« Reply #23 on: 25.07. 2019 20:56 »
RD..In an ideal world I would agree with you. But for a back on the road fix, it is well worth giving them another try. A little bit of slap and rattle may be perfectly acceptable rather than true perfection, bearing in mind the use the bike will have. OK, if it rattles and clanks too much, then a further investment is necessary, but for the sake of a few gaskets it is worth a try.

Owain... Just make sure the rings are free, and that the lands and skirts are nicely polished. Well worth another try with the bores honed to suit.

Swarfy.

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Re: Metal shavings in oil
« Reply #24 on: 25.07. 2019 21:57 »
3 thou would seize solid skirt pistons, I’m pretty sure.

I don’t know much about slotted pistons, but yours did seize.

Online JulianS

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Re: Metal shavings in oil
« Reply #25 on: 25.07. 2019 22:53 »
I would not risk pistons like that in my engine. I am also sceptical about the rings, I would have expected to see more bedding in, even after only 200 miles, you can see the blow by.

Are the pistons new hepolite ones? If yes some dealers refuse to sell them with the original rings, due to poor quality, and replace them with Italian GPM rings.


Online ironhead

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Re: Metal shavings in oil
« Reply #26 on: 25.07. 2019 23:07 »
Update: I've removed the engine and split the crankcases (at least, managed to remove the drive-side as I haven't managed to take the sprocket off timing side yet...).

I pulled the roller bearing off the drive side and the suspected shim was intact...but look at the state of these brand new pistons! (see attachment). As I mentioned the motorcycle has done less than 200 miles. Surely, this is not pistons should look like whilst running in the motorcycle?? I should also mention that during the first 100 miles, I had a few partial engine seizures whilst riding on the motorway. Although, could the huge amount crank end-float (0.021") have caused this amount of piston wear? 0.021". Irregardless, the bores on the cylinder don't look too bad (can't feel any scoring when running my finger nail down the cylinders) or maybe I'm letting my optimism blind me...Reckon the pistons are salvageable?


Owain, Looking at this picture of the piston it seems to have heavy scoring on the side. Have you another photo you could put up showing the front & rear skirts? ( could be more than just bore / piston clearance at play here)
SA

Online ironhead

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Re: Metal shavings in oil
« Reply #27 on: 25.07. 2019 23:29 »
I am taking it that "motorway" means 70 mph? Like our interstates? *eek*

 I think your break in procedure might be on the quick side.

Even more so with an outrigger attached  *eek* *eek*
SA

Offline BSA_54A10

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Re: Metal shavings in oil
« Reply #28 on: 26.07. 2019 07:33 »
I have been running in new rings "like I stole the bike" for near 20 years now and a seizure like that is not from careless running in.
The plugs & piston top will reveal if it was too lean and the underside will reveal if it was suffering from low oil.
As this is a new engine, nothing to loose from refitting the old pistons once they have been cleaned up.
The worst case is they might need to be replaced in a short amount of time.

Definately looks like bored way too close, the sort of thing that happens when a mechanic who has never worked on an air cooled engine knows better than you.
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Offline owain

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Re: Metal shavings in oil
« Reply #29 on: 26.07. 2019 11:44 »
I'll post some more pictures of the pistons after lunch. I tried cleaning one of them up but the scoring is still noticable all the way round. I'm using the A10 (when it is working) as a mid-long distance bike, so I'm starting to lean towards the side of biting the bullet and buying a set of new pistons now and get it done properly.

Yeah they were the new hepolite pistons and piston rings fitted. There is a shop nearby with some NOS A10 +060" pistons that might be worth paying the extra £30 for instead of a new set of hepolites... Then again, I never had this problem with my old bikes i.e. Triumph TR7 and BSA B33.
Sweden & North Wales
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'69 BSA A75R