Author Topic: Ew JP alloy piston ring gaps  (Read 551 times)

0 Members and 1 Guest are viewing this topic.

Offline hartleys1

  • Full Member
  • **
  • Join Date: Aug 2017
  • Posts: 33
  • Location: bradford west yorkshire ukm
Ew JP alloy piston ring gaps
« on: 22 Dec 2019 at 22:54 »
Hi
I will be fitting a pair of JP alloy pistons I purchsed over 10 years ago  to my 350EW sports.
The cylinders are bored to take 60.8mm pistons. I need to know the ring gaps.
If I had the paper work  its got lost. My question is
can I gap to .004" x  bore diameter top ring and
lower ring .005" x  bore diameter or both .004" which I beleive is standard ?
Hope someone can help.
Keith Hartley

Offline cardan

  • Master Member
  • ****
  • Join Date: Jul 2007
  • Posts: 1065
  • Location: Adelaide, South Australia
    • Leon's Vintage Motorcycle Page
Re: Ew JP alloy piston ring gaps
« Reply #1 on: 23 Dec 2019 at 09:42 »
Hi Keith,

Radco says 0.003" per inch of bore for a "cooking" engine, so something like 0.008"-0.010" would be a good number. Let me guess they are close to this out of the box?

Cheers,

Leon

Offline hartleys1

  • Full Member
  • **
  • Join Date: Aug 2017
  • Posts: 33
  • Location: bradford west yorkshire ukm
Re: Ew JP alloy piston ring gaps
« Reply #2 on: 23 Dec 2019 at 20:05 »
Hi Leon
All the ring gaps are 13 thou.
When the pistons were ordered they were for a 4thou clearence,but recently I was advised to increase the clearence to 6thou
because these pistons are prone to nipping up. So I had them re-honed,hence the incresed gap.
Thanks for replying so quickly. I hadn't looked at the Radco book.
Regards Keith

Offline Aero

  • Full Member
  • **
  • Join Date: Apr 2019
  • Posts: 97
  • Location: Shropshire
Re: Ew JP alloy piston ring gaps
« Reply #3 on: 23 Dec 2019 at 21:09 »
Hi Keith,
if the gaps are at 13 thou now they should be fine left as they are.
Its really not worth fitting new rings & gapping to a lower figure IMHO
Regards,
Mark

Offline cardan

  • Master Member
  • ****
  • Join Date: Jul 2007
  • Posts: 1065
  • Location: Adelaide, South Australia
    • Leon's Vintage Motorcycle Page
Re: Ew JP alloy piston ring gaps
« Reply #4 on: 24 Dec 2019 at 00:36 »
Yep and yep - 6 thou is better than 4 for the piston clearance, and 12 thou is fine for the ring gap.

I like Radco ("The Vintage Motorcyclist's Workshop") and have used it for most "advice" for years. Very practical approach to old engines.

Have a good Christmas,

Leon

 

motorcycle