Author Topic: Eastern pistons  (Read 5711 times)

Offline MG

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Re: Eastern pistons
« Reply #15 on: 16.07. 2010 21:05 »
Brian,
anything worth reporting about the pistons already?
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

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Online Brian

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Re: Eastern pistons
« Reply #16 on: 16.07. 2010 23:27 »
They are in the engine Markus but I probably wont have this one finished for at least 6 months. Its another plunger A10 I'm building.

While we are on the subject of pistons, a friend recently bought a pair of GPM's for his A10 so we weighed them bare, exactly the same as a set of genuine BSA ones. There seems to be a lot of different opinion of GPM pistons, I havent used any in a A but I have used them in B series BSA's without any problem. I had a good look at them and we measured the ovality etc and I would have to say it all looked good.

Online chaterlea25

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Re: Eastern pistons
« Reply #17 on: 16.07. 2010 23:47 »
Hi All,
Brian,
I had the same problem withe the ring gaps on the set I fitted recently
gaps were 25-30 thou???
Had to wait a week or more for a replacement set!!

Regards
John O R
1961 Super Rocket
1963 RGS (ongoing)

Offline a10gf

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Re: Eastern pistons
« Reply #18 on: 17.07. 2010 00:11 »
Totally off topic comment, sorry:

Brian, I admired the very good quality of your 003 photo above, and the exif info identified it as an old canon A410. Good to see one does not need the latest megagigabyte cam to get great photos. And great looking engine btw

A10 GF '53 My A10 website
"Success only gets you a ticket to a much more difficult task"

Online Brian

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Re: Eastern pistons
« Reply #19 on: 17.07. 2010 02:26 »
I got rid of the old HP Erling and have been using the other halfs A410, I still havent bought another camera, I'll get round to it oneday. (like a lot of other things)

Offline MG

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Re: Eastern pistons
« Reply #20 on: 17.07. 2010 07:37 »
Brian, thanks for the update.
I'll ask again in 7-8months, okay?  *smile*
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

www.histo-tech.at - Restoration, Repairs, Racing

Austria

Offline olev

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Re: Eastern pistons
« Reply #21 on: 20.07. 2010 13:08 »
Gday,
I've got hold of a set of 40 thou o/s pistons for the A7.
They seem to be about 8:1 CR.
The numbers on the packet say 67/1446 (Made in England)
The numbers on the piston say '67/1447 BSA'  '1mm OS'
then G over 46 inside a circle.
The closest match is Bacon's book which lists a 67/1442 as an 8:1 for 1958 - 1962.
They are solid skirt and weigh 7 gm more than the 7.25:1 originals.
Any thoughts on what I've got here? genuine BSA?
and why do they have oil holes into the gudgeon bushes if the pin isn't supposed to turn in the piston?
cheers

Online Brian

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Re: Eastern pistons
« Reply #22 on: 20.07. 2010 13:24 »
67-1446 is the part number and 67-1447 is the casting number. 67-1446 is correct for a 1mm or +.040" oversize 8-1 piston.

As for the brand, what was on the boxes? JP and GPM and the pistons I bought all come in clearly marked packets with the brand name on them.

I am not sure what pistons are made in the UK if thats whats on the packets. Hepolite come in distinctive boxes. All the genuine BSA pistons I have come across have the piled arms stamped into the top.

The gudgeon bushes have oil holes to let the oil in as the pins turn in the bushes.

Maybe you could post a photo of the packets the pistons came in and someone may recognise them.

Offline MG

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Re: Eastern pistons
« Reply #23 on: 20.07. 2010 13:29 »
Hepolites woud be split skirt, so are JPs.
The GPMs are solid skirt, and as far as I can remember they're marked with metric o/size values.
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

www.histo-tech.at - Restoration, Repairs, Racing

Austria

Online KiwiGF

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Re: Eastern pistons
« Reply #24 on: 18.08. 2011 09:13 »
Hello Brian I have just got std size flat top pistons from British only Austria and wondering how I can tell who made them as there are no manufacturing markings etc they look the same as yours And were circa 170nzd delivered

I got a few other prices for JP pistons NOS hepolites etc (all more than double the cost) but taking everything into account these pistons seemed the best bet being new lowish compression and lightweight
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Re: Eastern pistons
« Reply #25 on: 18.08. 2011 10:02 »
Hello Brian a quick check revealed the BOA gudgeons are 003 underside of 0.75 and the rings all have a 022 gap which will increase to over 025 when the barrel is honed to suit the pistons the max gap i think is 013

 I just wondered if I am unlucky and BOA have sent the wrong parts or if your parts are the same

The pins fit Far too easily into the pistons w/o warming them up and are also loose in my billet rods :-(
New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife)

Online BSA_54A10

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Re: Eastern pistons
« Reply #26 on: 18.08. 2011 10:52 »
Quote
I fitted the pistons today and discovered one problem, the rings. They had way too much end gap, .020". I had a set of Hepolite rings so I used them. Now I have a spare set for a STD or +.010" engine. Otherwise it all looks good.
No you do not have a spare set of + 20 rings.
It is a common fallacy that you can grind down a set of oversized rings to fit a smaller bore.
You can't.
The curvature will be wrong and the rings will apply very uneven pressure on the cylinder wall causing rapid oval wear of the bore.
You might get away with it in an emergency, like to get the bike back on the road fro the BSA National Rally ( cheesy plug ) but you should replace them with the correct size as soon as you get home.
Bike Beesa
Trevor

Online Brian

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Re: Eastern pistons
« Reply #27 on: 18.08. 2011 10:57 »
When I bought mine the pins were the correct size but the rings had way too much end gap, I cant remember exactly what the end gap was but it was at least .020" or more, I didnt use the rings but fitted a Hepolite set I had.

If your pins are loose in the rods dont use them. When you say billet rods I take it they have no gudgeon bush, the pins run directly in the rod. Do you have a set of original pins that fit the rod correctly, if you do heat a piston and see if the pin will push in. If it does you could use the pistons with different rings and pins. This of course means you would have to buy new pins and rings which probably makes the whole thing more expensive, alternatively you could send them back.

The ones I put in my engine have done just on 1,000 miles now and so far so good. It seems like they will run ok but time will tell what the wear will be like. I have a set of Hepolites ready to put in if these ones cause any trouble.

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Re: Eastern pistons
« Reply #28 on: 18.08. 2011 12:09 »
Hi Brian thanks for that I have some barely used pins and I could use them as they fit fine but I think I have the time to get BOA to replace the Pins and rings I'll post the results of that here......

I was going to buy pistons from JP but on this forum posters said JP rings were rubbish... so i don't feel so bad about the BOA rings being wrong I was sort of expecting it.

Apart from comments JP pistons were heavy and the rings rubbish the final straw was that it was cheaper to buy JP pistons from UK distributors like "red lizard" than direct from JP and even when I pointed that out to JP they refused to budge on price. JP also wanted twice the $ to ship from Aus to NZ than UK suppliers charge to ship to NZ!

I bought the SJ billet rods from thunder engineering Of the UK $550 nzd delivered and they supply SRM so I guess they are the SRM rods but cheaper also they arrived in NZ within a week and look great and yes there is no bush in the small end the only downside of these rods is the barrel cut outs will need to be widened by about 6mm as they are wider than OEM rods

I am not sure whether to simply take a grinder to the barrels or get the honer company to do it with a mill a slight concern with doing this widening is that the barrels have liners
New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife)

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Re: Eastern pistons
« Reply #29 on: 31.08. 2011 11:55 »
After a couple of weeks of waiting British Only Austria could not get a reply from the makers of the pistons (alledgedly a Taiwanese outfit) and they have asked me to return the piston as a set as they cannot replace just the faulty rings and gudgeon pins.

In addition they reckon they cannot "meet my requirements for this price"

My requirements being usable rings and gudgeon pins!

Pretty poor of British Only I reckon. I cannot recommend buying this type of piston set from them based on this experience

New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife)