Author Topic: What to do with old pistons  (Read 3145 times)

Offline BSARoadRocket

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Re: What to do with old pistons
« Reply #15 on: 05.01. 2013 08:19 »
To play the Devil's advocate...
   I say there is nothing wrong with using used parts.  New parts and perfection is nice, but sometimes the pocket book won't support it and it can be amazing just how far used parts can get you, even the worn out ones.  After all used parts are what get most of us to work every day. 

As a bit of automotive racing trivia early in Micky Thompson's racing career he could not afford to buy matched sets of new pistons for his  flathead V8 race motors.  He bought a boring bar and scrounged up what ever used pistons he could find and frequently  ran all different sized used pistons as that was all he could get.   

I once put together a super rocket motor on a budget that consisted of no money to spend. The only new parts that went into it was a set of rings and a drive side oil seal.   I  put used high compression pistons in a freshly bored cylinder with 5 broken fins and I cut out a spacer to put between the barrel and the case to lower the compression. 

I then took a worn out under-size timing bush and carefully scraped it out with a pocket knife and honed it with a wheel cylinder hone until it was a nice fit on my slightly worn standard crank. 

Yeah, it was a remarkably half baked rebuild job.  I figured it would hold together for a year and by that time I could afford to rebuild it right.   30K miles and 12 years later it's still running fine, has good compression and every time I've removed the timing cover I check the timing bushing for play and it's still tight!

Yeah...It's probably really due for a proper rebuild now but it still runs just fine with no funny noises so if it ain't broke don't fix it.



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Re: What to do with old pistons
« Reply #16 on: 05.01. 2013 11:28 »
 There once was a clever bloke in NZ that melted down particular types of pistons to cast his new ones. I recall he had a rather quick Indian.
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Online metalflake11

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Re: What to do with old pistons
« Reply #17 on: 05.01. 2013 11:45 »
Anthony Hopkins? wink2 *smile* *smile*
England N.W
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Online BSA_54A10

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Re: What to do with old pistons
« Reply #18 on: 05.01. 2013 12:37 »
Not totally off topic but when RR made their 6.25 Liter V8 which latter on became 6.75 L , twin turbo fuel injected V8 they used wet sleeves and no 2 pistons are in fact the same size.
You have to either buy a piston & liner set or get a new piston custom made.
Bike Beesa
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Offline baz

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Re: What to do with old pistons
« Reply #19 on: 05.01. 2013 14:05 »
as stated in this post it dpends on the size of your wallet and sometimes time restraints,i once blew the crown of a piston on my bike (triumph) the inlet rubber had split!! on my way to catch a ferry from harridge to the hook of holland i turned around limped home on one cylinder stripped the top end put in a used spare piston and caught the next ferry 9 hrs later the bike ran like that for a few years i was always skint then and not much better off now.......baz

Offline chaz

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Re: What to do with old pistons
« Reply #20 on: 27.01. 2013 21:02 »
just rebuilding an Ariel square 4 motor , customer wants to use original standard size pistons. as bores are ok I thought re ringing would be ok, his request , the other square 4 motor Ive rebored and got new pistons for,
new rings arrived and after a struggle I find pistons wont go in bores . on checking the new GPM rings are ok for end gap but are 0.020" thicker on wall thickness , thus making them 0.040" bigger on outside diameter. now grooves have to be re machined.

I suppose A7 and A10 were more plentiful so spares are worth keeping and new rings would be the right size.
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Offline JulianM

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Re: What to do with old pistons
« Reply #21 on: 29.01. 2013 07:47 »
Trouble is Chaz, when it all goes wrong the customer never says "well it's my fault for being a cheapskate, I should have let him do it properly"   they always say "what are YOU going to do about it!"  So a cheap job in reality means  "will you pay for it please? I'm too tight"

I got fed up with trying to do things cheap for customers with more money than me and then getting kicked for trying to help them. It now gets done how "I" want it or they go somewhere else!

For your self it's ok if you want to take a risk, but for customers, Never!

Just my opinion based on my own experiences.

Julian
55 Ariel HS mk1,
58 BSA Super Rocket Scrambler special,
60 BSA Gold Star, Jim hunter desert racer,
64 Norton N15CS,
65 Triumph TR6 SS,
66 Triumph Bonneville,
71 AJS Stormer,
71 BSA Rocket 3,
71 Laverda 750SF,
71 Laverda/Egli 750SF, Race bike,
73 Norton Commando 850,
74 Moto Morini 3-1/2 Sport,
74 Bultaco Sherpa 350,
76 Beta Cross 50,
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Re: What to do with old pistons
« Reply #22 on: 29.01. 2013 11:02 »
My own experience re used bits is very positive . I bought a 54 s/a A10 which when started sounded like the proverbial bag of spanners , both mains completely shot and the crank ( small journal ) knackered . Being like most of us (who were around in the sixties ) at 17 I was always skint but had friends one of these found a plunger motor from a guy who we knew , He was adamant that the motor was a good  'en and I took his word and paid the princely amount of £5 plus some bits I had for a bubble car ( one of Willies finest ) I just had an idea that the plunger crank would drop right in same as barrels and pistons fingers crossed etc. I stripped and cleaned and even polished the doner bits and the s/a cases, fitted new big end shells, moved the d/side main from plunger cases to s/a and in my nivety simply transferred the main . The result was a motor that started 1 time after I'd oiled by kicking it with plugs out until it returned to the tank , idled wonderfully and then wouldn't break no matter what I did to it!! and remember stupid a 17 yr old can be. I've often thought about that rebuild and would like to think that the extra care preparing everything before reassembly outwayed the s/hand element of the bits. I also remember another slant on the R/R info about 2 posts back, when selling Ford cars a couple of years later a brand new Cortina  wouldn't start, had to have the head lifted to sort it and every piston was a different size from standard to 40thou over all as sloppy as hell ,no compression worth speaking about ,selective assembly Ford called it ,you can imagine what we called it Regards BobH.   
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Offline JulianM

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Re: What to do with old pistons
« Reply #23 on: 29.01. 2013 18:27 »
I don't mean to say that using old pistons will never work, quite contrary, if they came out working fine then it stands to reason that they can go back in working, however to fit them to a new engine requires quite some messing and at the minimum new rings etc. So my point is why bother as the price of new pistons is so small.  And the risk of a problem, especially with a customers engine where parameters come into play that you can not controll is so high!

Regards,
Julian

typed fast so excuse any spelling mistakes.
55 Ariel HS mk1,
58 BSA Super Rocket Scrambler special,
60 BSA Gold Star, Jim hunter desert racer,
64 Norton N15CS,
65 Triumph TR6 SS,
66 Triumph Bonneville,
71 AJS Stormer,
71 BSA Rocket 3,
71 Laverda 750SF,
71 Laverda/Egli 750SF, Race bike,
73 Norton Commando 850,
74 Moto Morini 3-1/2 Sport,
74 Bultaco Sherpa 350,
76 Beta Cross 50,
77 Moto Guzzi Le Mans Mk1,
80 Ducati 900 MHR,

Offline chaz

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Re: What to do with old pistons
« Reply #24 on: 29.01. 2013 18:59 »
wise words Julian, but I have tried to get him to buy new ones but does not want to go that way , and now Ive got 2 suppliers of oem standard piston rings he is happy.. will be a caveat on his bill
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Offline JulianM

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Re: What to do with old pistons
« Reply #25 on: 30.01. 2013 07:59 »
Must say that I would love to see the SQ4 when it's running again. Extremely special motorcycles!   I just swapped mine for a rather special Gold Star Scrambler.  Finding out some really interesting race history about it now!   Will fill the hole again shortly though  ;)   (as soon as the wife is not looking)

Julian
55 Ariel HS mk1,
58 BSA Super Rocket Scrambler special,
60 BSA Gold Star, Jim hunter desert racer,
64 Norton N15CS,
65 Triumph TR6 SS,
66 Triumph Bonneville,
71 AJS Stormer,
71 BSA Rocket 3,
71 Laverda 750SF,
71 Laverda/Egli 750SF, Race bike,
73 Norton Commando 850,
74 Moto Morini 3-1/2 Sport,
74 Bultaco Sherpa 350,
76 Beta Cross 50,
77 Moto Guzzi Le Mans Mk1,
80 Ducati 900 MHR,

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Re: What to do with old pistons
« Reply #26 on: 30.01. 2013 10:33 »
Wouldn't dream of contradicting you Julian, to much respect for your engineering prowess ,simply giving an example and really possing a question ,did my motor turn out reasonably good simply because I was lucky or was it due to extra care I took, no meticulous care I took putting it back together? Also not put from any commercial point either , if I pay I want the best and I expect to pay well for the services of the guy doing a good job hence when I rebuilt my present motor I used SRM for all the engineering work and paid accordingly for a good job, didn't show the receipts to the wife though!! No back then in 1967 ( I was 17 ) I was simply risking about £10 and my time ,a completely different proposition than that of customer / engineer and of course it added to my knowledge and experience which in itself is priceless to an enquiring mind which fortunately I was blessed with, best wishes BobH. ps any new piccys of the project ?     
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Offline JulianM

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Re: What to do with old pistons
« Reply #27 on: 31.01. 2013 07:57 »
 *smile*  Don't worry about contradicting me, I can be as wrong as the next man and often more so  ;)

You are absolutely right!  It's not actually "What you put in" rather "The way that you put it in"   an idiot can mess up even the best ingredients where as time, patience, knowlege and experience can make even the worst ingredients sing.   However the cost in time goes up exponentially the worse the ingredients are, and this is what customers regularly fail to understand.  Where as if we fail to understand that on our own jobs we usually pay the price as fuckitty fuck shit fuck fuck fuck! I will do that better next time  ;o)   We've all been there!

Julian

55 Ariel HS mk1,
58 BSA Super Rocket Scrambler special,
60 BSA Gold Star, Jim hunter desert racer,
64 Norton N15CS,
65 Triumph TR6 SS,
66 Triumph Bonneville,
71 AJS Stormer,
71 BSA Rocket 3,
71 Laverda 750SF,
71 Laverda/Egli 750SF, Race bike,
73 Norton Commando 850,
74 Moto Morini 3-1/2 Sport,
74 Bultaco Sherpa 350,
76 Beta Cross 50,
77 Moto Guzzi Le Mans Mk1,
80 Ducati 900 MHR,

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Re: What to do with old pistons
« Reply #28 on: 31.01. 2013 09:27 »
I tend to say bugga a fair bit. *smile*
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7