Author Topic: Piston choice - Hepolite or JP?  (Read 2380 times)

Offline Slymo

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Re: Piston choice - Hepolite or JP?
« Reply #45 on: 08.10. 2018 11:34 »
There were lots of "Sacrifices to the Gods of Speed" on his shelve that is true. I too would happily use a JP piston again but I will source the rings from somewhere else.

Offline coater87

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Re: Piston choice - Hepolite or JP?
« Reply #46 on: 08.10. 2018 22:13 »
 Didnt Wisco make some decent A10 pistons at one time?

Central Wisconsin in the U.S.

Online chaterlea25

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Re: Piston choice - Hepolite or JP?
« Reply #47 on: 08.10. 2018 22:43 »
Hi Lee,
Cake St Classics had Wiseco make a batch some years ago
They were 9:1 compression
I do not know if they are still available
I have a pair to go into the RGS engine build

1961 Super Rocket
1963 RGS (ongoing)

Online Colsbeeza

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Re: Piston choice - Hepolite or JP?
« Reply #48 on: 09.10. 2018 02:33 »
Hi Steve,
I went through the headache of finding rings recently for my Flash. It has new bores at 70.5mm, but were glazed with only 40 miles running due to issues I have detailed elsewhere on the Forum (Smoking), so replaced the rings as a precaution. The pistons were 25yo Hepolites, so presumably English-made.
I purchased a set of Gandini rings locally with the specification on the package blotted out due to the poor condition of the package. The ring measurements did not match the old Hepolite rings.
I finally purchased a set of AE Hepolite rings from SRM, being fairly confident that they know their stuff.
The AE's did match the original spec and also my old rings, although the AE's do have more Back clearance - along the lines that Hastings recommend. I have attached the measurements, which also show clearances both either top/bottom of the ring and back clearance.
If you are matching new rings to existing pistons, the only advice I can give is to make sure the supplier is prepared to take them out of the package and measure both the thickness and depth before parting with your hard-earned. After trying this with Draganfly for two weeks, I gave up.! *problem* They did eventually do so, but by then I had already ordered from SRM. Draganfly's new Gandini ring spec did also match.
After getting the head done up, de-glazed the bores and fitted the new rings, I have re-assembled and run the bike fairly hard but variable for 5 miles - still some smoke and oil on left cylinder. *eek* Given the issues I found with the engine, I was just too smuggly confident to check the breather system and a few other smoke sources. Those little jobs will be next before I do serious miles on it. Geez it ran like stink though.!!

Offline Steverat

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Re: Piston choice - Hepolite or JP?
« Reply #49 on: 10.10. 2018 22:06 »
Hi Col
Burton Bike Bits very kindly sold me some new Hepolites with some NOS British Hepolite rings. I'll take your point and have a look at he clearances before I bolt everything up.

1951 BSA A10 - now returned to Germany
1972 Triumph T100R Daytona
1924 B-S SS80
1965 Triumph SH Cub
1960 AJS M18CS

Online RDfella

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Re: Piston choice - Hepolite or JP?
« Reply #50 on: 10.10. 2018 22:22 »
Colsbeeza - am surprised at the variation between rings in your table. The measurement that's most important (assuming there's adequate back clearance) is the fit in the lands. Too much gap, and the lands will fail through hammering. Too little and the gases won't be able to get behind the ring to seal it to the cylinder wall or, worse still, the ring will get nipped in the piston and fail to seal at all. From your list, it seems OE Hepolite is the only correct match.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online berger

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Re: Piston choice - Hepolite or JP?
« Reply #51 on: 24.02. 2019 22:33 »
steve there's this thread to refer to people have mentioned suppliers

Offline Rocket Racer

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Re: Piston choice - Hepolite or JP?
« Reply #52 on: 25.02. 2019 03:32 »
On a Norton Atlas I used JP's and nothing but problems with several sets, I wouldnt use them again if I was paid to, but know people that both swear by, or at them.  I fall into the latter camp. Seize the day is their motto  *whistle*
Have a set of +80 Gandini's awaiting fitment to my road rocket but the compression ratio is a bit low as for a track motor.
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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Online ironhead

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Re: Piston choice - Hepolite or JP?
« Reply #53 on: 25.02. 2019 04:25 »
As groily mentioned earlier JP's need at least 0.005" skirt clearance. They grow & always have.

Offline Scott and Jay

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Re: Piston choice - Hepolite or JP?
« Reply #54 on: 07.03. 2019 01:50 »
On this topic I like to refer back to my posts on IMD pistons and rings - better, I believe - than either JP or Hepolite (made in UK)..