O-Ring mod for $100ish USD - hope it works

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Hooligan
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Joined: Mon Aug 20, 2012 1:37 am
Location: Calgary, Alberta

Re: O-Ring mod for $100ish USD - hope it works

#16 Post by Hooligan » Tue May 23, 2017 4:03 pm

I am partial to placing the O-ring groove on the cylinders. Less to go wrong there and much easier to assemble as gravity helps rather than hinders.
'82 RD350LC in '81 colours, OEM pipes, UNI filters
'85 FZ750

bitzz
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Location: Omemee, Canada

Re: O-Ring mod for $100ish USD - hope it works

#17 Post by bitzz » Tue May 23, 2017 6:16 pm

I cut the head.
Over the years I have replaced the cylinders 4 or 5 times... still using the same heads.
I glue the O ring in the slot with a spot of grease.

graham heise
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Location: gold coast Australia

Re: O-Ring mod for $100ish USD - hope it works

#18 Post by graham heise » Wed Jun 21, 2017 7:29 am

what is the ideal inner / outer diameter and depth of the trench for the oring in the the head? is there a common oring size used?
yamaha fanatic.

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JanBros
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Re: O-Ring mod for $100ish USD - hope it works

#19 Post by JanBros » Thu Jun 22, 2017 12:47 pm

graham heise wrote:what is the ideal inner / outer diameter and depth of the trench for the oring in the the head? is there a common oring size used?
the O-rings can not be squished together, they only deform.
so if you take crossections : the one from the trench needs to be a tiny bit bigger than that of the ring.
I make the trench just as wide as the ring (prevents the ring from falling out on assembly) and make the depth 20% less than the the diameter of the ring.
for example : crossection of a 2mm ring = Pi x R² = 3.14 mm²
crossection of trench = 2 x 1.6 (80% of 2) = 3.2 mm²

you should try to leave 3mm of material between the combustion chamber and the trench
if it runs, you can race it !

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motosapien
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Re: O-Ring mod for $100ish USD - hope it works

#20 Post by motosapien » Thu Jun 22, 2017 2:16 pm

https://oringcalculator.eriksgroup.com/" onclick="window.open(this.href);return false;
2>4

graham heise
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Re: O-Ring mod for $100ish USD - hope it works

#21 Post by graham heise » Fri Jun 23, 2017 8:39 am

Thank you for the reply gents. I have read every post on this forum regarding modifiying a stock rz 350 head for optimum performance. From what i understand the basic mod description is. o'ring the head, .9mm squish, 14 deg squish band angle, squish band width 40-45 percent of bore diameter, 19 to 20cc volume, 7.2 to 7.5 corrected compression (130-145psi) for a tuned ported road race engine? Is this the basic formula? I have 2 heads and a local engineering shop down the road (iron horse engineering) who i hope can do the work.
Let me know if i am wrong on the specs. I'll post the outcome once done.
yamaha fanatic.

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