Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties Question about oil control piston rings

Question about oil control piston rings

Post Wed Sep 14, 2016 12:12 pm

Posts: 21
Location: somewhere near Stratford, Ontario Canada

Hi, I have a 74" UL with re-sleeved cylinders stock bore, with brand new NOS HD pistons. The rings have a one piece solid oil control ring with no windows. My machinist wants me to go to a Hastings three piece ring with the corrugated center oil ring for better oil scraping and an easier time for the oil to find it's way in to the windows in the piston. Is there any reason not to follow his advice and keep the cast oil ring, or is an updated modern Hasting style oil ring a better choice? Thanks.


Posts: 118
Go with the upgraded rings. the old oil rings are 1930 tech. the 1950s type work much better.


Posts: 111
a modern cast strutted piston using shovelhead type rings would be a big improvement. my 39 U consumes so little that i need not add any between oil changes, these pistons are readily available too.


Posts: 358
I use hastings rings myself. Company wise we sell hastingrings and OEM rings. From none we ever have any real issues.

There are theories of how the thin oilscraping rings could cause more pressure on the cylinder and thus eating away the walls faster, but as far as I know this has never been empirically proven.

There are clearly people that are Pro old type rings and people that are pro hastings type rings. I suppose in the same way that there are people that are pro multigrade and anti multigrade oil. It depends what features you give more importance.


Posts: 111
i have repop cylinders with 45k miles on them. one is standard bore and the other is .10 os due to a scratch from a bit of trash in the wrist pin. the hasting rings have been very kind to my bores. i have honed the cylinders twice for new rings since the top end needed to come off to address valve cover leaks. i do run multi weight 20/50 synthetic with a 1/4 quart of marvel mystery oil. i ride this bike every day i can and take vacation trips of 1500 to 3000 miles routinely for the past four seasons. wish you the best with your U model, set up right they are a rock solid riide.


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