Author Topic: Hepolite pistons and camshafts  (Read 5811 times)

Offline Rocket Racer

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Re: Hepolite pistons and camshafts
« Reply #15 on: 14.02. 2010 03:10 »
Pleasing to hear the JP's work well on A7's, I had 9:1 comp JP's on a Norton Atlas motor and they caused me nothing but grief. They were also quite heavy. Both sets seized with the second set must have had a hairline crack in as one seized after a few minutes light running and had a visible crack in after disassembly. I ended up putting in Wiseco's and that sorted it. Perhaps in a road motor they might be ok. But I'd never use them myself given any sort of choice.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Offline MG

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Re: Hepolite pistons and camshafts
« Reply #16 on: 14.02. 2010 09:12 »
Rocket Racer,
I agree, the JPs are ok for road use, but I would not use them for a racing engine. There's nothing better than a good FORGED piston for high performance use due to the higher material strength.
I had problems similar to yours with the Italian GPMs in the A10, I think I told the story in another thread already. Many others use them without any troubles.
I don't really know what the reasons for this discrepancy are, maybe its large manufacturing tolerances, insufficient quality assurance or finally just the riding style, no idea.
But like the crack in your JPs the problem with my GPMs definitely had been a mistake somewhere in the manufacturing process, the solution for me were the Wisecos, too.
But unless you are able to find a set of good Hepolites, there aren't any alternatives for the A7 I would know of. All the JPs I have fitted to several bikes so far actually never caused any sort of problems.

What I always do now before fitting new pistons is to temper them prior to fitting. I measure the diameter of the new pistons on several positions and directions and then slowly heat them up to 250°C (this is the maximum temp. the kitchen oven can deliver, but I suggest to wait 'til the better half is absent to avoid discussions similar to the one that occurs when you get caught cleaning cycle parts in the dish washer  *eek* ;)) and let them cool down, I do this 3 or 4 times. When finally cooled down I measure again and check for any irregularities (residual deformations, visible cracks, etc.).
This way you have a chance of seeing the results of geometric irregularities or material imperfections and reduce residual stresses from the casting process.

Speaking of the piston weight: All pistons for the A7/A10 range I have seen so far are significantly heavier than the Hepolites, which in turn were slightly heavier than the original BSA pistons as well. The Wisecos I fitted to the A10 aren't really light-weight either, I think they they were around 4 or 5 grams heavier than the GPMs, if my memory serves me right.

Cheers, Markus
1955 A7 Shooting Star
1956 A10 Golden Flash
1961 Matchless G12 CSR

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Offline mike667

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Re: Hepolite pistons and camshafts
« Reply #17 on: 14.02. 2010 12:42 »
Lyford Classics have them listed in their catalogue std,+20,+40 and +60 might be worth a call if you haven't already
tel 01773 768900
or http://lyford-bsa.co.uk/home.html

All the best - Bill

Lyfords A10 piston (at least the 8.5:1 cones) are the italian cast GPMs - according to PAt at Lyford (who swears by them)  -know they have mixed reviews here....

Online bsa-bill

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Re: Hepolite pistons and camshafts
« Reply #18 on: 14.02. 2010 14:00 »
-know they have mixed reviews here...

I bought pistons from Lyford but they are A10 9.5 and IIRC made in Australia, can't say anything about them yet as they've yet to meet a spark *conf*.
I'm confused are we looking for A10 or A7 pistons now

All the best - Bill
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline alanp

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Re: Hepolite pistons and camshafts
« Reply #19 on: 14.02. 2010 14:04 »
On the subject of piston weight, does anyone have the weights of Wiseco pistons compared to JPs on A10, standard size? If Wisecos are heavier by some relatively small amount I'd consider getting a pair from Cake Street and carefully take metal out of them in some unstressed area to match the weight of the JPs to avoid screwing up the dynamic balancing my crank assembly with JPs has had. I used a Wiseco piston in my Gold Star and was happy to rev it really hard.
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Offline mrshells

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Re: Hepolite pistons and camshafts
« Reply #20 on: 14.02. 2010 15:42 »
Im looking for A7 pistons
allthough I have got hold of some perfect used +40 hepolite
and the barrel is being bored to match them
I phoned Lyford and to be honest hes taking the P**S  110 for GPM pistons each !!! 

Online bsa-bill

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Re: Hepolite pistons and camshafts
« Reply #21 on: 14.02. 2010 17:46 »
ouch, I didn't pay that much for mine, pretty sure it was around £130 or so, looks like his online catalogue is out of date as it is stating £110 for A7 and a bit more for A7 long stroke and clearly states for a set (2), even with postage and VAT it should not come anywhere near his quote.
Just been down the shed to check receipts ( not to be recommended ) but couldn't find one for the pistons so maybe I got them elsewhere, pretty sure I remember having a conversation with him though upshot of which was the Italian ones were heavier and the Aussie ones were good.
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline BSA_54A10

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Re: Hepolite pistons and camshafts
« Reply #22 on: 15.02. 2010 02:50 »
I fit a lot of JP's and am generally happy with them.
They did have a problem with rings a while back but they seem to be on top of that now ( wrong rings supplied ).
This is not a problem for me as I buy them bare and fit Total Seals with a gapless second ring.
Bike Beesa
Trevor