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JP pistons Australia ....any good? #688443
03/17/17 8:49 pm
03/17/17 8:49 pm
Joined: Oct 2007
Posts: 1,520
Auckland NZ
Ignoramus Online content OP
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Ignoramus  Online Content OP
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Joined: Oct 2007
Posts: 1,520
Auckland NZ
i am going to have to replace pistons in A10 std . Ive heard mixed reviews about JP pistons some say they are great, some say they are junk

any comments from those who have used them successfully or other wise ?

I will likely go for the semi dished (medium compression option) or stick with whats there fully dished lowest compression.

Thanks Guys


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
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Re: JP pistons Australia ....any good? [Re: Ignoramus] #688446
03/17/17 9:45 pm
03/17/17 9:45 pm
Joined: Jun 2002
Posts: 913
Jaffrey, NH, USA
Peter Quick Offline

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Peter Quick  Offline

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Jaffrey, NH, USA
The JP Pistons I have handled are massive and heavy compared to any other similar pistons. I have said they are good for driving in tent stakes if short a hammer. Looks like they were milled out a big block and a bit too much material was left behind. They will definitely change the balance. And folks have absolutely nothing good to say about JP rings. The lumps I have seen are over 10 years old so I don't know if JP has improved since then.


check out: www.bsaunitsingles.com
2500 BSA part numbers with inventory in stock just for the unit singles!
Re: JP pistons Australia ....any good? [Re: Peter Quick] #688486
03/18/17 6:46 am
03/18/17 6:46 am
Joined: Oct 2001
Posts: 1,106
Sydney, Oz
S
Shane in Oz Online content
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Shane in Oz  Online Content
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Joined: Oct 2001
Posts: 1,106
Sydney, Oz
JP appear to cast pistons to the maximum oversize and then machine them down for the lesser oversizes and standard, so the weight depends on the oversize.
On the plus side, they will make weird and wonderful pistons if somebody can provide an old example for a pattern, which was great for my Sloper.

I think A10 Std pistons are still available from other manufacturers, so worth looking for alternatives.

As far as JP rings go, they may not be a problem on 2-ring pistons such as the Sloper.

Re: JP pistons Australia ....any good? [Re: Ignoramus] #688499
03/18/17 10:40 am
03/18/17 10:40 am
Joined: Apr 2007
Posts: 768
Brisbane, Australia
BrizzoBrit Offline

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BrizzoBrit  Offline

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Posts: 768
Brisbane, Australia
Ig,

In the feedback I've seen and the conversation with only one owner who used them (500 Dominator) best steered clear of if possible it seems

Ray


BSA 1969 A65F
BSA 1966 A65H
Triumph 1968 T120
Kawasaki A1R
& too many projects!
Re: JP pistons Australia ....any good? [Re: Shane in Oz] #688500
03/18/17 10:47 am
03/18/17 10:47 am
Joined: May 2004
Posts: 3,639
Sydney Australia
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BSA_WM20 Online content
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Joined: May 2004
Posts: 3,639
Sydney Australia
Yes I have used JP pistons on several cars & bikes without problems.
Weights do seem to vary a bit, some can be lighter than originals while others are heavier.
AS for the rings, totally unsuitable for use in a British Iron bore, they will take a long while to bed in if at all.
A friend runs JP's in his Douglass, C10 & G14 ( one only in the twin ) without any problems after he fitted proper rings.
I have on in the M20 right now and I had one in a WDB40, both worked fine .
They are cast so not as good for hard use as JE's but for every day riding absolutely fine remembering that the crank will most likely need to be rebalanced.
We had this out on another forum and it ended up the JP was the closest to Std weight, but that was more good luck than anything else.

I would have though that you could get Std A 10's in the shaky isles without much hassle .


Bike Beesa
Trevor
Re: JP pistons Australia ....any good? [Re: Ignoramus] #688544
03/18/17 7:49 pm
03/18/17 7:49 pm
Joined: Oct 2007
Posts: 1,520
Auckland NZ
Ignoramus Online content OP
BritBike Forum member
Ignoramus  Online Content OP
BritBike Forum member
Joined: Oct 2007
Posts: 1,520
Auckland NZ
Interesting comment about the rings being no good ...........thats what ive been told . Trevor : you cant get much here these days , our biggest and best supplier has gone down hill recently.

I hadn't even thought about the weight issue , but considering how much more work it is to balance the crank than just do the pistons I will probably just cross my figures and put whatever pistons i get straight in and see how it runs ,,, if no good i will then do the balance act.

Looks like no one is that keen on JPs so far ........

Last edited by Ignoramus; 03/18/17 8:01 pm.

"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: JP pistons Australia ....any good? [Re: Ignoramus] #688710
03/20/17 3:19 am
03/20/17 3:19 am
Joined: Feb 2014
Posts: 971
Lancaster, California
C.B.S Online content

Parts Dealer
C.B.S  Online Content

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Joined: Feb 2014
Posts: 971
Lancaster, California
I heard JP pistons are usually heavy?

Re: JP pistons Australia ....any good? [Re: Ignoramus] #688733
03/20/17 9:15 am
03/20/17 9:15 am
Joined: May 2004
Posts: 3,639
Sydney Australia
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BSA_WM20 Online content
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BSA_WM20  Online Content
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Joined: May 2004
Posts: 3,639
Sydney Australia
Originally Posted by Ignoramus
Interesting comment about the rings being no good ...........thats what ive been told . Trevor : you cant get much here these days , our biggest and best supplier has gone down hill recently.

I hadn't even thought about the weight issue , but considering how much more work it is to balance the crank than just do the pistons I will probably just cross my figures and put whatever pistons i get straight in and see how it runs ,,, if no good i will then do the balance act.

Looks like no one is that keen on JPs so far ........


British Spares were never much chop with BSA stuff & I stopped ordering from them in the 80's after 3 wrong shipments in a row.
Even worse was the excuse, "some on put the new parts in the wrong bin".
If you don't know what the parts look like you should not be selling them.
I think I still have some credit slips from them somewhere.

BJ's bike bits in Qld are good and Mike Reily is even better and he for sure will have std A 10's in stock with good rings.


Bike Beesa
Trevor
Re: JP pistons Australia ....any good? [Re: Ignoramus] #688792
03/20/17 8:34 pm
03/20/17 8:34 pm
Joined: Oct 2007
Posts: 1,520
Auckland NZ
Ignoramus Online content OP
BritBike Forum member
Ignoramus  Online Content OP
BritBike Forum member
Joined: Oct 2007
Posts: 1,520
Auckland NZ
Trevor ive had (untill the last few years) good success with british spares but their stock is way diminished these days ............will try the place you quoted in QLD cheers


"There's the way it ought to be and there's the way it is" (Sgt Barnes)

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