Hepolite Piston Direction

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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Hepolite Piston Direction

Postby Yves.Astein » Sun Mar 10, 2019 1:02 am

Hi All,

I am about to drop new Hepolite pistons into my 59 G12. Unfortunatly I dont know the direction they need to go in. They are the ones with a round head and they have a cut away on one side for a valve to clear the top of the piston. So the question is, does the cut away need to be on the inlet side or the outlet ?


Thanks for your advice.

Yves

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Re: Hepolite Piston Direction

Postby clive » Sun Mar 10, 2019 11:06 am

The 59 G12 spares list illustrates a piston with two cutaways. I am confused that a piston may need a cutaway for one valve only. Are you sure its right for your bike?
clive
if it ain't broke don't fix

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Re: Hepolite Piston Direction

Postby Yves.Astein » Sun Mar 10, 2019 11:37 am

Hi Clive,

I certainly hope its the right one. I actualy have 2 sets. And they both look the same. I bought them independantly supposedly siutable for 59 G12. As I have been reeding, 59s was a special year in terms of Pistons. Before and after the used different shapes...

I have added a picture

Image

On the verry left is the one I am replacing. To me it looks like, the cutaway is not realy required. Because the origional one is completly the same but without the cutaway...

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Re: Hepolite Piston Direction

Postby Yves.Astein » Sun Mar 10, 2019 11:41 am

Ahhh, 15036 is for sure the right one:

http://www.jampot.com/forum/viewtopic.php?f=21&t=8762

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Re: Hepolite Piston Direction

Postby clive » Sun Mar 10, 2019 2:12 pm

They are not completely the same as the dome in your new one is higher. It will give a higher compression and is why the cut out is there. Cannot help with which way it should be fitted. Can anyone with more knowledge of the 59 G12 help?
clive
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Re: Hepolite Piston Direction

Postby ajsph » Sun Mar 10, 2019 2:24 pm

The cut out is for the inlet valve
Poul

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Re: Hepolite Piston Direction

Postby Yves.Astein » Sun Mar 10, 2019 5:21 pm

Its amazing, the way you guys are helping.
I cant thank you enough.

Thank you !!!!

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