Author Topic: parts mix  (Read 1289 times)

Offline andy2565

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parts mix
« on: 08.01. 2011 10:46 »
hi all
i was wondering about which parts fitted from other bikes or motors in general,engine wise what pistons have people used.
 i've heard of someone using datsun pistons,and mini pistons,what about a65 or triumph pistons ? would they fit,and rods,i read on on of the other threads that someone used triumph rods,it seams the a7 is more tunable than the a10,what have people tried would be interested to hear.being a grass track rider i was wondering if the jawa valves were similer,if they wre this would mean you could use the alloy collars and collets.
 i would always expect some work involved in fitting anything different,but sometimes worth a try.
near wolves uk,will keep riding as long as can stay upright,tribsa,tt500,2xJAP grasstrackers+jawa.gold flash.triumph metisse,and others.

Offline trickytree

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Re: parts mix
« Reply #1 on: 08.01. 2011 11:19 »
Chap I know used flat top Mini 1275 pistons in his A10 but only so he could add squish bands to the head...not a 5 minute job but worked well
1965 A65 Bobber
A10 Bitza project

Offline BSA_54A10

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Re: parts mix
« Reply #2 on: 08.01. 2011 12:15 »
As a general rule you can not run water cooled pistons in an air cooled motor.
Usually they re too thin in the skirt and can not handle the large clearences needed in out bikes and fail in a very expensive way in a short time.
Then there is the supply & demand rule.
Using a + 60 what not piston instead of a standard BSA one simply means that those who make quality replacement parts will stop doing so because the volume is too low and when it is time for your rebore you will end up with plasticine pistons turned up by blind unckle Ahmed on this treddle lathe.
BSA parts are not expensive.
A piston for my SR 500 was $ 125 Aus, bare, extra for the rings , extra for the pin & extra for the clips.
$ 205 all up. In those days a pair of Hepoiltes for an A10 was $ 95 .oo and if NOS came with an extra set of rings.
Bike Beesa
Trevor

Offline trickytree

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Re: parts mix
« Reply #3 on: 08.01. 2011 12:32 »
Quote
As a general rule you can not run water cooled pistons in an air cooled motor.
Usually they re too thin in the skirt and can not handle the large clearences needed in out bikes and fail in a very expensive way in a short time.

Thats a fair point but in this case were not talking about Ford Zetec engines, were talking BLMC A series, an engine almost as archaic as our beloved British vertical twin. I should however have said that the chap in question did send the pistons to Camcoat...heat barier on the top, some teflony type coating on the sides and they were also coated under the crown... and so they run at much tighter clearances than an engine of this type would normally. Plus the 1275 piston in question is a slipper design, so shorter in skirt and lighter than a standard A10.





1965 A65 Bobber
A10 Bitza project

Offline Stu55Flash

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Re: parts mix
« Reply #4 on: 08.01. 2011 14:18 »
Rob Waddle from Newcastle who reworked my A10 bottom end can do an +0.5 mm rebore (I don't know but these maybe Datsun Cherry 100A standard size = 73mm??) over the +60 thou and fit Datson pistons. Apparently the pistons available now are not the same quality as the hepolite.  Datson pistons are a good match in quality terms!

Stu
"Keep a distance from lady "L" drivers in cars. Some are not mechanically minded, are slow to acquire road sense, an are apt to panic..." The Pitman Book of the BSA Twins.
Golden Flash Plunger 1955, Francis Barnett Falcon 67 1954, Ferguson TEA Tractor 1951. Looking for another project!

Offline charlieb1954

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Re: parts mix
« Reply #5 on: 08.01. 2011 14:25 »
that newcastle in england   thats real intresting as got few a10 barrels on + 060   thanks for that
may you do what you can today as tommorrow you may not be able to

Offline andy2565

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Re: parts mix
« Reply #6 on: 08.01. 2011 16:04 »
i did wonder about the water verses the air called subject but the datsun pistons worked out 1.5mm lower in the barrel,are the a65's completely different,my thought was if you wanted to build something different,using the bsa cases and barrel etc,what would fit inside
 i just compared an xt500 exhaust valve to the rgs inlet.same length and about 1mm wider on the head,maybe a consideration for the racers.
near wolves uk,will keep riding as long as can stay upright,tribsa,tt500,2xJAP grasstrackers+jawa.gold flash.triumph metisse,and others.

Offline olev

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Re: parts mix
« Reply #7 on: 09.01. 2011 10:15 »
This post of Andy?s is overdue and I hope anyone who has successfully used alternate parts will add to it.
I?d be rapt if someone told me the pistons out of a Yamasaki or BMW thousand are 67mm and will drop straight into the A7.
Eg: will the 67mm pistons out of the triple fit?
Can any of the rods out of the squillion modern bikes be made to fit? Does anyone have a list of eye to eye distances of various rods?
A while back I bought a head off a gent who owns a machine shop. The valves he fitted are slightly oversize and came out of a Toyota Camry (I think he said). They look great.

Trevor,
Maybe I?ve been living under a log but I thought all those who make quality replacement parts have stopped doing so long ago.
Even my genuine OEM BSA A7 piston set has slightly different diameters.
I?m currently running a Suzuki PE250 piston in my Greeves. It?s a perfect fit and of a quality far superior to anything Greeves ever dreamed of. I find it hard to believe with all your experience of BSAs and modern japanese machines you haven?t found interchangeable parts. Your recommendations seem to stop at oil and batteries. Please don?t take this as criticism as I value your tips and posts. (just finished installing rings using stilsons ? brilliant)

Back in the 60?s (they reckon if you can remember them you weren?t there) car engines gave 100k miles before a major rebuild. Since the late 80?s the engines get twice this.
I reckon we?d be crazy not to take advantage of the advances in oils, metallurgy and machining tolerances that will make our engines more reliable.
Cheers

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Re: parts mix
« Reply #8 on: 09.01. 2011 11:59 »
G'day Olev,
               have a look at Dan's land speed record post. A few interesting ideas there. I have used trident pistons but had to shorten A10 rods to do so.
Cheers
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Offline andy2565

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Re: parts mix
« Reply #9 on: 09.01. 2011 12:42 »
the main issue i find with the japanese pistons is that the pin in higher,if you could use longer rods,then maybe some gs450 pistons or machine off a fin as stated on that website,muskat how did you shorten your rods at the big end ?i've heard of a company that can shorten rods by heating them,which ends up with a bulge in the middle,but this is a max of 1mm.
 if your a horder and have collected loads of parts,you would have the advantage of being able to try other parts to make a mongrel of an engine,but for those of us that dont have the parts it great hearing of other people trying things out,theres got to be some steel rods off a car somewhere that would fit.oh but theres always the issue of the through bolts if you take the compression to high.
near wolves uk,will keep riding as long as can stay upright,tribsa,tt500,2xJAP grasstrackers+jawa.gold flash.triumph metisse,and others.

Offline BSA_54A10

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Re: parts mix
« Reply #10 on: 09.01. 2011 12:54 »
Yes there have been massive changes to production engineering and tollerances on modern engines which are better than a blue printed gold star motor. But modern engine parts are made for modern engines.
Running a rod from an over square modern buzz box in a long stoke slow reving bearing pounder will have it falling apart in no time flat. Rods are designed to handle the forces generated by the lighter pistons, in a faster reving better cooled engine.
Most water cooled pistons are very thin and even worse for us, round , as the barrel they are running in is water cooled and  kept at a relative stable temperature thus there is little dimensional change from dead cold to full heat, and better cooling allows it retain its roundness .
Our barrels are anything but round and change dimensions drastically and non uniformly to boot.
Modern engines have substantially better oil delivery systems and many of them actually have metering jets to control the oil flow to again tight tollerances.
I would be estatic if I could find some good substitute pistons to fit my A7s,. I have 4 in parts, 2 being the early longer stroke engines and every piston that I have found so far has either been given away or flogged on evilbay as I was not happy with any if them.

What I was trying to say in a rather clumsy way there is more to the selection of an alternative part than " will it fit in the hole".
Even things like valves can give grief as again , car valves run in water cooled, constant temperature heads with in some cases regulated oil flow and valve stem oil seals. They do run at any where near the temperatures that our bike valves do. They are also designed for a much lighter duty cycle and are made from substantially lower grade steels than our original valves.
Other things like modern oil seals, yes go for it, better materials & better made , sealed bearings , fine solid state electrics , big tick.Belt drive primaries , what a good idea, clutches grafted from Yammies or Suzukis great
Bike Beesa
Trevor

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Re: parts mix
« Reply #11 on: 09.01. 2011 13:09 »
G'day Andy,
                just dug out my old book. Shortened A10 rods 3mm by taking 3mm off the rod and cap mating surfaces then re-bore the hole. I can't remember the exact amount of crush for the shells, I think it was 4 thou. Or you could make eccentric little end bushes and go 1.5mm at both ends.
 I wish I had the money to horde parts and experiment. I just get what I need and hope it works.
Cheers
 Just saw Trevor's post and agree. If swapping parts I would look for something around the same era and type eg air cooled and Pommie
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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