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650SS piston selection

Submitted by ian_richtsteig on Wednesday, 10 September, 2014 - 01:00
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Heavy Twins

Just started to rebuild my 605SS engine after needing to repaint after being hit from behind by a 4x4 driver.

I am going to fit a replacement barrel as the current barrel is cracked at the bottom of the skirt.

My spare barrel needs a rebore due to a pit mark so I have the choice of pistons from my spares:

i) A & E "Covmo" standard bore flat top pistons or

ii) OEM Norton Shenstone spare parts +20 thou GPM pistons with a slight dome.

Interested in what others think I should use. My preference is for the flat top pistons due to modern fuels.

thanks, Ian

Submitted by gordon_johnston on Wednesday, 10 September, 2014 - 01:01

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I would go for the lowest compression ratio pistons I could get. The octane rating of petrol is significantly lower now than it was when our bikes were new. I don't suppose octane ratios will increase in the future, so keeping the CR down would make sense.

Submitted by ian_richtsteig on Monday, 15 September, 2014 - 01:00

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Previously Gordon Johnston wrote:

I would go for the lowest compression ratio pistons I could get. The octane rating of petrol is significantly lower now than it was when our bikes were new. I don't suppose octane ratios will increase in the future, so keeping the CR down would make sense.

Thanks Gordon. You have reinforced my plans. I use 98 octane unleaded here in Oz which is ethanol free and the 650SS and my 750 Roadster perform well on it.

thanks,

Ian

Submitted by rajiv_raghavan on Friday, 19 September, 2014 - 01:00

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Ian,

If I may piggy back on your thread , does anyone have any feedback on the Jap/Taiwanese/Australian pistons and rings please .

I am rebuidling my 62 Domi and considering these options vs Hepolite which is about three times as expensive

Any feedback will be greatly appreciated

Cheers

Rajiv

Submitted by gordon_johnston on Friday, 19 September, 2014 - 01:02

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I have used Taiwanese pistons and rings on one of my BSAs. Absolutely fine after may thousands of miles. My Atlas is running on pistons from Norvil - Italian made I think. Again no problems. Hepolite rings are fine too, but in my experience there appeared to be a bad patch in production some years ago when I had a number of Hepolite pistons fail which rather put me off them.

Submitted by rajiv_raghavan on Monday, 22 September, 2014 - 01:00

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Gordon , Thank you very much for your feedback and I will be going ahead with the Taiwanese option

Cheers

Rajiv

Previously Gordon Johnston wrote:

I have used Taiwanese pistons and rings on one of my BSAs. Absolutely fine after may thousands of miles. My Atlas is running on pistons from Norvil - Italian made I think. Again no problems. Hepolite rings are fine too, but in my experience there appeared to be a bad patch in production some years ago when I had a number of Hepolite pistons fail which rather put me off them.

 



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