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A65 OPRV question #787192 10/16/19 3:39 am
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Mark Z Offline OP
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Need to replace the OPRV on a '67 A65L; this one is visibly "shot" (cruddy and rusty). What should I look for in a replacement, used, NOS, aftermarket? Is there a way to test it?

One supplier claims a Triumph OPRV, which is domed instead of flat like the BSA one, will fit. Would this be a suitable replacement?


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
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Re: A65 OPRV question [Re: Mark Z] #787201 10/16/19 5:26 am
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NickL Offline
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The triumph one will be fine, although the original late beezer domed one had one extra vent hole in
the gap between the threads. Just make sure it 'bottoms out' and seals well on the threads.
The early bsa one has a small ball bearing that works as the relief seal, the late types use a piston as
does the trumpet one.

Re: A65 OPRV question [Re: Mark Z] #787245 10/16/19 7:06 pm
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The dome type OPRV will work

Make sure you get the one for the twins and NOT the triples as the screen / spring rate is not the same

Also, BSA used the Triumph type starting in 1970 - on but early models can be retrofitted


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Re: A65 OPRV question [Re: Mark Z] #787250 10/16/19 7:27 pm
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Allan Gill Offline
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Avoid the stainless types


beerchug
Re: A65 OPRV question [Re: Allan Gill] #787268 10/16/19 11:42 pm
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Mark Z Offline OP
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Thanks all! Is it necessary to put any sort of sealer on the threads?

Originally Posted by Allan Gill
Avoid the stainless types


Allan, can you elaborate?


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: A65 OPRV question [Re: Mark Z] #787272 10/17/19 12:18 am
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Is it necessary to put any sort of sealer on the threads?


Yes, apply pipe sealer goo to the female threads furthest down the hole, better than putting goo on the male threads and wiping most off or into the oil ways before it gets to the critical deep threads which seal the inner HP zone. of course its nearly impossible to do this with all the oil present, its a good idea to drain the lines and blow through to have a chance of clean prep.

i have no personal experience with SS OPRVs
, but, I do know from other workings that running SS against SS is a bad idea, in many hydro power applications its inevitable, and so is "pickup", SS has higher friction properties compared to say Brass, its not as slippy, when two SS surfaces say Hello they grab, its not pretty..
.

Last edited by gavin eisler; 10/17/19 12:20 am.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
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Re: A65 OPRV question [Re: Mark Z] #787274 10/17/19 12:26 am
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NickL Offline
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If you lean the bike over toward the drive side, clean out the orifice with plenty of clean rag and a drop of petrol,
some loctite 518 can be applied to the inner threads. That seems to work very well.

Stainless is not always such a great material, BUT it's shiny so people love it.

Last edited by NickL; 10/17/19 12:28 am.
Re: A65 OPRV question [Re: Mark Z] #787296 10/17/19 6:43 am
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As described, it’s cosmetically nice but sticks and galls inside on the piston. All 3 I’ve looked at have all been knackered. In some cases had to put a small drift through the mesh to tap the piston out.

If you look on eBay, a seller had loads of new old stock piston types, still in the brown paper and with part number paper. I bought a few but so far used one, stripped it and cleaned it then sealed the threads on the dome but with RTV sealer. It’s never been a problem since.


beerchug
Re: A65 OPRV question [Re: Mark Z] #787469 10/19/19 5:37 am
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Never quite understood SRM's logic, or lack thereof, in making the valve from stainless. I can kind of understand using it for the body, but the piston is constantly in oil. Just poor engineering, for the reasons given already.
I've had one show scratches after less than 1000 miles!


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: A65 OPRV question [Re: Mark Z] #787479 10/19/19 9:25 am
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Its an engineering no no to use the same material for both rubbing surfaces, as both are exactly the same on a molecular level they try to become part of each other when static and then when moved pluck bits out of each other. Making the plunger out of bronze would work well leaving the rust free stainless body to do its thing.

Re: A65 OPRV question [Re: Mark Z] #787480 10/19/19 9:39 am
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Cast iron would be easy to make the plunger from.


Amateur Loctite enthusiast.
Re: A65 OPRV question [Re: Mark Z] #787529 10/19/19 11:08 pm
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As i said, it's shiny so people love it. Like heaps of other stainless stuff which is not appropriate.
If they made those OPRV's with a chrome cap, they'd sell hundreds just the same.

Advertise them as 'Billet' and you'd sell even more.

Re: A65 OPRV question [Re: NickL] #787537 10/20/19 12:17 am
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Mark Z Offline OP
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Originally Posted by NickL
As i said, it's shiny so people love it. Like heaps of other stainless stuff which is not appropriate.
If they made those OPRV's with a chrome cap, they'd sell hundreds just the same.

Advertise them as 'Billet' and you'd sell even more.


Not to worry; I'm way past that sort of nonsense. Back in the 1980s, I had the primary, outer timing, and rocker covers chromed on my '67 Lightning. The chrome on the rocker cover yellowed from heat, and my pants cuff scuffed the chrome on the primary and timing covers. Not fixable, and won't win any points at a serious show anyway.

I love stainless steel hardware, talking about standard stuff that doesn't thread into a part and just has a nut on the end. Won't rust, and it can be cut to length if necessary without exposing a surface to corrosion. You can even grind the markings off the bolt heads if you're so inclined. But I know enough to stay original when it comes to stuff like engine hardware, especially head bolts and the like, and I would see no point in having a shiny OPRV.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
Re: A65 OPRV question [Re: Mark Z] #787542 10/20/19 1:42 am
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in another life when i was a component manufacturer i made more stainless threads than you could count (auto lathes ect), standard practice was to always reduce the od of the male part to give more clearance for exactly the reasons (gauling) as outlined above. Always only aimed for 60% or so thread (ie larger tapping diameter , specially with 316 ........didnt snap so many taps that way and it made little practical difference to thread strength.

agree with Mark Z ..........i love stainless fasteners as well, just for nuts and bolts, (on the A65) much to the irritation of purists but still cant bring myself to use cap screws.... just the wrong look


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: A65 OPRV question [Re: Ignoramus] #787556 10/20/19 6:33 am
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Originally Posted by Ignoramus
in another life when i was a component manufacturer i made more stainless threads than you could count (auto lathes ect), standard practice was to always reduce the od of the male part to give more clearance for exactly the reasons (gauling) as outlined above. Always only aimed for 60% or so thread (ie larger tapping diameter , specially with 316 ........didnt snap so many taps that way and it made little practical difference to thread strength.

So maybe SRM also cut the threads this way, leading to leakage past the valve? More moronic, "engineering"!


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: A65 OPRV question [Re: Mark Z] #787565 10/20/19 8:28 am
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The threads that fit into the case would be SS to alloy , no need to allow clearance for galling, the area of concern is the sliding fit of the piston, this needs to be close for the valve to operate correctly.
On a pedantic spelling note , Gaul = France, to gall = to rub together. see entry three below.

gall noun (1)
\ ˈgȯl
\
Definition of gall

(Entry 1 of 4)
1a : bile especially : bile obtained from an animal and used in the arts or medicine
b : something bitter to endure
c : bitterness of spirit : rancor
2 : brazen boldness coupled with impudent assurance and insolence had the gall to think that he could replace her

gall noun (2)

Definition of gall (Entry 2 of 4)
1a : a skin sore caused by chronic irritation
b : a cause or state of exasperation
2 archaic : flaw

gall verb
galled; galling; galls

Definition of gall (Entry 3 of 4)

transitive verb
1 : to fret and wear away by friction : chafe the loose saddle galled the horse's back the galling of a metal bearing
2 : irritate, vex sarcasm galls her

intransitive verb
1 : to become sore or worn by rubbing
2 : seize sense 2

gall noun (3)

Definition of gall (Entry 4 of 4)
: an abnormal outgrowth of plant tissue usually due to insect or mite parasites or fungi and sometimes forming an important source of tannin — see gall wasp illustration


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A65 OPRV question [Re: Mark Z] #787609 10/20/19 7:05 pm
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yep mocking a typo is real constructive ..........

Pedantic means "like a pedant," someone who's too concerned with literal accuracy or formality. It's a negative term that implies someone is showing off book learning or trivia, especially in a tiresome way.

not a bad definition eh.


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: A65 OPRV question [Re: Mark Z] #787613 10/20/19 7:17 pm
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Some people would thank him.


Amateur Loctite enthusiast.
Re: A65 OPRV question [Re: Mark Z] #787624 10/20/19 8:47 pm
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I wonder if two stainless steel parts gall together in Gaul?

Re: A65 OPRV question [Re: Tridentman] #787625 10/20/19 8:54 pm
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Ignoramus Online Content
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Originally Posted by Tridentman
I wonder if two stainless steel parts gall together in Gaul?


considering it was the French that invented stainless very likely.......ive heard that ss was invented by accident when some foundry worker put way too much cr into a melt pot and they dumped the batch outside and eventually noticed it didnt go rusty......thats the story anyhow


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: A65 OPRV question [Re: Mark Z] #787681 10/21/19 6:30 am
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DavidP Offline
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Hell is a place with French engineers, German lovers, Italian politicians, and English cooks.


Stepping on others doesn't make you stand tall.

71 A65L "Zelda"
92 BMW K100rs "Gustav"
72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
Re: A65 OPRV question [Re: Ignoramus] #787688 10/21/19 8:32 am
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re Spelling gall .
It wasnt aimed at anyone in particular, i see this word miss spelled more often than I see it spelled correctly on this site.
I accused my self of pedantry, not anyone else. My apologies to any offended.


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56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A65 OPRV question [Re: Mark Z] #787733 10/21/19 7:00 pm
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Ignoramus Online Content
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Thanks Gavin for that ........and yes i did see that you claimed to be a pedant which is why i helpfully provided a workable definition. ......internet things can get a bit like the sandpit squabbling eh i do it myself occasional.,,,,,,,,,,NOW.......... back to BSAs


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: A65 OPRV question [Re: Mark Z] #787735 10/21/19 7:56 pm
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Gavin--no apologies necessary.
In my view we deal with some good Brit bike stuff on this forum---and if sometimes we track off topic--well-- no problem--it normally leads into something interesting---and in my view that is what life is all about.
Just my two cents worth of course.

Re: A65 OPRV question [Re: Mark Z] #787811 10/22/19 10:36 am
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And just to go even more off topic.
It is called Galling because the parts actually expand as would be the case when a plant has been infested by a gall wasp.
It is the expanding oxide coatings that actually stick together.
Weather it is a problem or not depends upon the strength of the oxide.
Stainless low temperature oxides are very tenacious so they stick to each other stronger than they stick to the surface that they grew from so when forced a par, all of the oxide will be on one part and the other will have what appears to be hole in the metal.
It actually is not a holeit is a hole in the oxide coating, but when the hole oxidises to the same depth as the rest of the coating then you have the start of a gall pit.


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