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Re: OPRV Leak Test [Re: Hillbilly bike] #720496
12/30/17 3:06 pm
12/30/17 3:06 pm
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Re: OPRV Leak Test [Re: DMadigan] #720524
12/30/17 9:27 pm
12/30/17 9:27 pm
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Rotherham - S. Yorkshire
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Gentleman, this is a very interesting an informative thread, David has a wealth of knowledge on these bikes that many of us could only dream of knowing. I ask politely that you extend the courtesy and learn from what he is trying to teach, I’m sure, that like many of us he has work and family to which he could spend his valuable time. The fact he gives us that time to educate us and impart knowledge that has taken a long time and finance to learn is something we should all be grateful for. As previously mentioned if you don’t have anything of worth to bring to the party, no evidence to prove him otherwise then please don’t rock the boat. There can only be theoretical values of what you should be achieving and a tolerance from there... the wear of every engine is different and there will be other variables too.

In addition to this, I strongly advise that the back chat on this forum and this post especially ends now. Simon you have been notified by other valued forum members, however as one of the moderators for this forum I ask all participants to move forward with this topic and not the actions of an individual. I ask that those members make an edit to their posts.

Thankyou for using the forum.

Allan


beerchug
Re: OPRV Leak Test [Re: Allan Gill] #720527
12/30/17 9:57 pm
12/30/17 9:57 pm
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quinten Online content
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Why not add a ball top/and seat... to the piston design.
ball and seat... would eliminate piston seepage when fully closed

Necessary piston seepage wouldn't matter when ball is unseated.

The piston-slide should still offer , more than adequate regulation if the ball/seat component is contaminated
And the piston slide design offers a way to more easily graduate the pressure pop off.

.

Re: OPRV Leak Test [Re: triton thrasher] #720543
12/30/17 11:28 pm
12/30/17 11:28 pm
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Originally Posted by triton thrasher
As a user of a piston type valve in another well-known make of 650 twin, I had never considered seepage between piston and bore before.

The ball relief valves in BSAs were replaced by Triumph types as an improvement, but it looks like they brought with them the issue of loss at low rpm.

Ball valves have a safety disadvantage in that the ball can be held open by dirt, allowing serious loss of oil. With full-flow filtration by a real filter between pump and relief valve, that wouldn't be a problem, but there is no real oil filter on an A65 (or a Bonneville).


The ball valve will clean itself more readily in use than the piston type, once the piston has wedged open with any contamination it isn't washed away like it would be on a ball valve. Six and half a dozen.....
So really it's down to fitting a filter in either case.



Re: OPRV Leak Test [Re: NickL] #720547
12/30/17 11:45 pm
12/30/17 11:45 pm
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I probably missed it
but
Has an estimated optimal or minimum oil flow rate , at high and low rpms,
for all the engines total collective bearing journals been establihed ?


.

Re: OPRV Leak Test [Re: DMadigan] #720554
12/31/17 12:11 am
12/31/17 12:11 am
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Bolton Lancs UK
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There is not a problem as such with the OPRV. The oil pump is marginal at low RPM, then at high RPM when it should be relieving the pressure the passageways are too small to pass the oil. This is compounded by owners who think that thick gloopy oil must be "better" It will not pass down the passages when cold resulting in high pressure spikes that can destroy oil seals and damage oil pumps


1955 BSA B31 400cc "Stargazer"
1962 Greeves 200cc "Blue Meanie"
1962/67 Greeves 350cc
1967 Greeves 360cc Challenger
1984 Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500cc sprint/LSR bike "Deofol"
Jawa 500cc grasstrack
2003 Aprilia RSV Mille "Lo Stregone"
Re: OPRV Leak Test [Re: DMadigan] #720566
12/31/17 2:16 am
12/31/17 2:16 am
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Brisbane, Australia
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OK, results are in on my road test of 'sealing' the last 3 threads of the OPRV on my 69 A65F.

In this instance, I found a 2-4 psi increase after 'sealing' the threads. I'd call call that worth getting with a simple 'trick'. Effect greater at higher pressures (as might be expected). Overall max pressure didnt change much (~ from 40 up to 42 psi at 4-5k rpm). Ride conditions were the same between runs although oil temp in tank was ~ 80oC for the first run and ~ 83 for the second.

The synthetic seems to run overall lower psi than the dino oil I used previously in line with its reduced viscosity.

Not sure how good a job I did of this as I have only ever done this sealing before with the engine on the bench. For this time around, the engine was in the frame and the exhaust pipe blocked ready access.

Pressure was read from a temporarily fitted pressure gauge (SAAS fluid filled fuel pressure gauge, reading 0-100psi).


Cheers
Ray


BSA 1969 A65F
BSA 1966 A65H
Triumph 1968 T120
Kawasaki A1R
& too many projects!
Re: OPRV Leak Test [Re: DMadigan] #720574
12/31/17 4:23 am
12/31/17 4:23 am
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I thought DMadigan was using a two stage gerotor oil pump.

Re: OPRV Leak Test [Re: DMadigan] #720577
12/31/17 5:39 am
12/31/17 5:39 am
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David did produce a very nice gerotor pump. I offered him $100.00 for one, and never heard back................. grin


What weight oil are you using Ray?



Re: OPRV Leak Test [Re: BrizzoBrit] #720593
12/31/17 1:36 pm
12/31/17 1:36 pm
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Ray,

That is good news. In a low flow, low pressure system, 2 - 4 PSI increase is significant. And this is a fix that is almost free to do!

I have done this on the bench and on a bike. Definitely easier on the bench.

Did you eliminate the seal washer and go to an O-ring for the valve body?

Be happy you had 3 threads to work with. I have seen less than 2. The arrangement of the OPRV cavity and the angle drilling BSA did for the drain is poor. Not sure which is worse, the OPRV cavity or the oil manifold and ports feeding the pump. Both are pretty poor. eek


Life is too short to drink cheap, bad beer.
Re: OPRV Leak Test [Re: DMadigan] #720692
01/01/18 2:51 am
01/01/18 2:51 am
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Nick and Rich. I was pretty hasty in posting yesterday. Initially felt it wasn't much difference, but then on reflection I realised its a 5-10% overall gain in pressure. I have gone back to look at DM's bench test to review his outcome (which I should have done yesterday) which suggests a few psi at 10psi pressure. So maybe the 2 different tests are suggesting fairly similar outcomes. If you squinted you might say the gain was 4 psi at lower engine speeds. DM will have used room temp oil whereas I reported for hot oil.

I dont run an oil pressure gauge normally because its a distraction. Certainly there was a big difference in observed oil pressure between cold and hot. Nick, I've used Penrite MC4 V-twin 20W-50. Was all I could get over the break as I hadn't got organised. I didn't realise I wouldn't be able to get Mobil 1 V twin at the local Repco. The spec sheet shows a cSt for the synth (100oC) of 17.4 compared to 24.2 for HPR30 which I typically use and I have (yes, as you have chided me about) also run HPR40 (28.6) 'gloop' at times. Mobil 1 is quoted at 20.8.

Hard for me to comprehend whether lower pressures equates to more flow and better lube/cooling or more leakage losses in the pump and elsewhere. Oil temps recorded were similar for the synth and previous measurements with dino oil.

Rich, previously I measured up the distances inside the housing (as you suggested in a post more than 10 years ago) and used 2 fibre washers to space the OPRV so that the relief hole and rebate in the threads lined up with the relief gallery in the cases. Yesterday I replaced those fibre washers, which were old, with a single aluminium washer that was sort of close in thickness to the 2 fibre washers. The OPRV have been venting oil to the environment and not just down the relief gallery. I still have a persisting leak in that area somewhere (not OPRV) I'm about to follow up on. I have been tackling the big things first and I dont have a lot of spare time for messing around.

Id like to see more than 40-42 psi above 4k so will now go back and review the pump. I did this fiddling because previously I had replaced the o-ring inside the oil pump with what i could scrounge in the shed. I'd ordered some, but the parts book number is incorrect and specifies a 3/16 x 1/16 when a 5/16 x 1/16 is required. I bought some viton ones of the correct size and installed one of those over the break. In the pump there was no real scoring on the bottom end plate, but what I haven't checked is the clearance between the gears and endplate for the feed side which might use some tweaking. Whenever I have checked oil pressure previously I have always been happy with it and got OPRV blow-off pressure pretty much above 4k. I also sealed between the pump body and endplates with the lightest smear I could get of Permatex which is a gloopy and maybe I should convert to an anaerobic sealant??

I'll post any positive findings.

Cheers
Ray


BSA 1969 A65F
BSA 1966 A65H
Triumph 1968 T120
Kawasaki A1R
& too many projects!
Re: OPRV Leak Test [Re: DMadigan] #720702
01/01/18 7:14 am
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Ray, the fibre washer or copper washer etc must be thin enough to allow the valve to 'bottom out' in the cavity or you'll never get it to seal properly.
Spacing the valve out will make matters worse not better.
Your bike should give more than 45psi as it's an end fed setup i think. You are loosing a lot of oil somewhere.
The 18-20cst at 100 degs is about right for a 20-50.oil.

Most of the pumps leak at the joints between the sections, easy check fill the pump with oil and rotate with one hand while blocking the exhaust
side off with your fingers. if the pump body is distorted then the joints will leak. Your fingers can contain 40psi over that area quite easily and you'll see the leaks.
Most sealants are way too thick for the pump faces, a smear of welseal is all i use. Using a thick sealant can actually make matters worse as the
faces cannot pull up together.



Re: OPRV Leak Test [Re: NickL] #720827
01/02/18 1:53 am
01/02/18 1:53 am
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Yes, thanks Nick. End-feed crank. I'm concerned by this so will pull timing cover and have a look around. I feel I should be getting better based on past experience. I'll pull the OPRV again also.

This is a different gauge to previous runs so I'll check against another. The gauge I used previously died so cannot compare directly.


Cheers
Ray


BSA 1969 A65F
BSA 1966 A65H
Triumph 1968 T120
Kawasaki A1R
& too many projects!
Re: OPRV Leak Test [Re: DMadigan] #721117
01/05/18 1:25 am
01/05/18 1:25 am
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OK folks, I have important updates on this after having redone some things with brain engaged.

After failing to get what I thought was good oil pressure I revisited a few things to check for potential weak points. Pulled, the timing cover and removed oil pump. Dismantle and check. Some wear on the top cover with the drive shaft. Lapped this and the bottom cover plate, also each side of the body to remove the fairly rough machining marks (see images). Do Nick's suggestion of finger over the outlet. Pressure was improved but still some leakage, sounded/felt like it might have been leaking between the gears which have visible 'wear'. Some leakage at top plate without sealant, but pump was assembled with a light smear of loctite 518 rather than gloopy Permatex.

Replace end-feed oil-seal. Painful job as the high pressure seal I use (3.5bar) is 20mm whereas the hole was cut at 3/4" so I have to grind a bit of the seal to fit. Killed 3 seals in the process until I got one right. Hole size will be fixed next time this comes apart. The 'regular' seal that was initially installed inverted a couple of times. These have a rating of only 0.5 bar so a useless solution in this application. The cases when prepared by the engineering shop came with a note not to exceed 45psi and adjust my OPRV accordingly. What sot of solution for low oil pressure is that?!

Button everything back up again and check the piston type OPRV (fitted as an 'upgrade'). Dismantled, cleaned and all looked fine. Put it back together and hear a rattle. Dismantle again. Compare to one (Triumph presumably) dragged out of the bag of bits. It had preload on the spring when cap going on and spring was 1.40" (close to spec of 1 3/8"). Spring in mine was ~0.9" Fiddle around a bit. On cold oil I get OPRV blow-offs of ~90 (full length spring), ~95 short spring with 2x 0.056" washers as shims, ~65 (short spring 1x 0.056 'shim') and ~ 50 (short spring). OK, failing memory kicks in and I recall 10 years ago 'adjusting' the spring to get 50psi blow-off on cold oil. This does mean the piston is part way along its travel in the resting state.

When I pulled the OPRV and thinking about comments above it was clear to me that cavity looked much deeper than then OPRV (see images) and I had previously applied sealant only to last 3-4 threads of the cavity. This had achieved a 4-6psi increase in hot oil pressure. So I reinstalled the OPRV (now set set for ~65 psi) into the OPRV cavity with no sealing. Go for a run. Pressure no better than before without seal in the OPRV cavity and possibly worse. At 3k getting ~24-26 psi, 2 1/2 k 20-22psi, idle barely a reading so maybe 2-4 psi. Pressure starts to fail at oil temp of ~70oC (did a series of oil temp checks).

So measured everything up (see diagram - apologies dimensions in mm) and it was clear I had probably missed the bottom of the OPRV with the sealing attempt. I believe when I did thss way back I measured all this stuff and sealed in the correct place relative to OPRV (the only good thing about having a poor memory is you do lots of things for the 'first time' smile ). So I thought I'd do the sealing properly this time. Cleaned the cavity thoroughly with methylated spririts, applied Loctite 518 to the 4 threads immediately internal to the relief gallery hole (N.B. - NOT at the bottom of the cavity). Reinstall OPRV allow to cure overnight.

Take for a run VOILA!!!!!!!

Cold, pressure pegged at ~62 psi from > 1500 rpm. With hot oil (~80oC) the blow-off pressure seemed to be about 52-54 psi. First notable observation I think. That this blow-off pressure goes down with hot oil. Anything over 3k gave anywhere between 48 - 54 psi depending on conditions (ie pretty much pegged at blow-off). 2k gave 24-26 psi (equivalent of 3k previously) and at idle anywhere between 6-10 depending on idle speed.

So, my previous attempt at analysing this underestimated the value of sealing the relevant threads of the OPRV. Estimated gain at 3k ~20 psi or better. This was more like I expected. My apologies for getting this wrong.

So: i) engage brain before doing anything, and ii) and you probably all had pegged already, measure up so that sealant is installed exactly where required.

I'll buy some new feed side gears to fit in the pump for the next time I take the oil pump out.

Ray

Attached Files IMG_2108.jpgIMG_2109.jpgIMG_2171 resize.jpgscan0003.jpg
Last edited by BrizzoBrit; 01/05/18 1:34 am. Reason: clearer diagram

BSA 1969 A65F
BSA 1966 A65H
Triumph 1968 T120
Kawasaki A1R
& too many projects!
Re: OPRV Leak Test [Re: DMadigan] #721126
01/05/18 4:47 am
01/05/18 4:47 am
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Nice one Ray glad you got a result.
As a future thing you could have the OPRV machined to take an o-ring under the head instead of using a washer,
the old type valves were done that way, in my opinion it's the best way.


Nick


http://www.partzonline.co.nz/seals-imperial-c-100_314_865.html

Last edited by NickL; 01/05/18 5:14 am.


Re: OPRV Leak Test [Re: NickL] #721129
01/05/18 6:57 am
01/05/18 6:57 am
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Thanks Nick,

I was pretty happy with this. Hopefully there is some guidance here for others. Not to follow my stupidity, but for the things to consider.

I agree the o-ring is a great way of doing this. I found my stash of OPRvs and the ball-type I took off was in there and it has o-ring grooves. Just for fun I put it on, but it gave zero pressure so I didnt persist. The ali washer is 0.036" and the fibre washers I have 0.028" I've had dribbles in the past with the fibre washer, and found I was doing them up pretty tight. To will see how the ali washer goes. It got loctite 518 both sides of the washer. I like to get these oiltight and never touch them again until necessary. I prefer riding to tinkering.

Getting everything sorted in advance for my annual ride down to Sydney for the festival of speed and the International rally later in the year.

Its funny how we 'upgrade' things without perhaps knowing the whole story. The idea that if its of a later model it must be better, may not always be so.

Ray


BSA 1969 A65F
BSA 1966 A65H
Triumph 1968 T120
Kawasaki A1R
& too many projects!
Re: OPRV Leak Test [Re: DMadigan] #721130
01/05/18 7:22 am
01/05/18 7:22 am
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So leakage past the thread is significant. Too bad you do not have a good ball valve to compare leakage past the piston.
From the picture of the OPRV cavity, you have a late case with the drain back into the return drilling instead of the sump. I just looked at the earlier case an the steep angle of the port only leaves two threads from the end so the leakage is likely worse.
If the pump were higher capacity the leakage would not be a problem but managing the extra flow would be with the small diameter of the drilling.
Perhaps you should tighten the OPRV without the fibre or aluminum washer and use a feeler gauge to see how thick it should be. I think if you can bottom the OPRV and get the washer to seal it would be best.
You should look into a hydraulic seal for the end feed. They are made for higher pressures.

Re: OPRV Leak Test [Re: DMadigan] #721139
01/05/18 10:39 am
01/05/18 10:39 am
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The early cases with the angle drilling drain are the worst. 2 threads are typical to seal. That is marginal. I have seen worse.

IMO, the angle drilled cavity is the source of a lot of the reputation the A series unit twins have for oilining issues. It is a shyt design.

Using sealant on the lower threads seems to work for me for a long time. And seating the OPRV as deep into case as possible as well. But after this thread, I am starting to wonder if some sort of elastomeric seal will fit at the end of the OPRV to provide additional seal. Guess I may have to play around to see what is possible.


Life is too short to drink cheap, bad beer.
Re: OPRV Leak Test [Re: DMadigan] #721142
01/05/18 11:41 am
01/05/18 11:41 am
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DM, yes these are 69 cases (NC1419x). Yes, sorry was getting a bit fed up by that stage. If I'd known I was going to recover so much pressure with sealing I'd have spent more time fiddling with the ball OPRV. OPRV cavity is very deep and would be hard to get this particular OPRV to go all they way to the end. Threads on the OPRV stop about 1/8" shy of the end of the threads in the cavity. Maybe I'll think of some things to try before I pull this apart again, but the first iteration of this stayed together for nearly 10 years.

Of the OPRVs I looked at (all Triumph I presume) this one looked to have about the most thread. A full 3 threads all the way around. Maybe that's why I picked it to use way back when. My memory is too dull to recall that. Threads in the cavity are not particularly tight on the OPRV as it slops a round a bit. I think slowly, so now I'd consider next time I do this to try some selective fitment.

RB, I appreciate all the post you made about this way back close to when I built this bike in 2007. I believe it has led to the good longevity of this engine. I just need to think about things a bit instead of getting impatient. I always have my insights after I have finisged something.

I used to treat this as set and forget, but think I will want to monitor oil pressure occasionally to ensure the sealing hasn't failed. Yes some sort of 'bridge' structure with with an o-ring groove might work in a deep cavity like this.

Cheers
Ray


BSA 1969 A65F
BSA 1966 A65H
Triumph 1968 T120
Kawasaki A1R
& too many projects!
Re: OPRV Leak Test [Re: DMadigan] #721198
01/05/18 8:42 pm
01/05/18 8:42 pm
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Great article Ray and this prompted me to go and measure the OPRV and oil gallery on my 68 A65.

Despite my bike being the earlier type, the measurements of the oil gallery are pretty much the same as yours, see pic below.

My SRM OPRV also has similar dimensions to yours but is narrower in between the threads where the relief hole is (3mm vs 4.5 on yours). Mine is also longer by 1mm which is mostly because the threads nearest the oil inlet are 1mm longer (5mm vs 4mm on yours).

I checked the OPRV spring length and its 1 3/16, I'm assuming this is correct as its only a few years old with relatively low miles. The piston seemed to be in good condition as well.

I've cleaned the oil gallery with solvent and used anaerobic thread locker on the innermost threads as suggested and its currently drying overnight.

Will report back later on what the oil pressure is like, hopefully in a similar range to yours.

[Linked Image]

[Linked Image]


Last edited by gunner; 01/08/18 8:00 am.

1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Re: OPRV Leak Test [Re: DMadigan] #721200
01/05/18 8:47 pm
01/05/18 8:47 pm
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argyll. scotland, uk
Good work Ray, it seems that loose fitting OPRV s are almost a cert on these motors, mine was exactly the same , I used a cotton bud for the inner female part past the blow off hole, and same on the male outer before the valve blow off, pipe sealer stuff that i borrowed from the bike shop. Many thanks to Rich B for pointing all this out originally. Cleaning this up when oily is a chore. Your pump doesnt look too bad, very decent result, SRM should have new gears.

I like NickL 's plan to use the dump line as valve gear lub, if any new OPRV could have this option built in, I would jump on one of those.

My bike still wears its original OPRV , I put a new spring in it once about 20 years ago, probably due a fresh one.

Perhaps if the valve is to be re made the thread tolerance could be a bit tighter.Maybe the factory was worried about cracking cases ?
I dont fret a lot about low speed valve leakage, keep the revs up. The OPRV main job is to blow off and prevent overpressure, as long as it does that I am good with it. When cold I keep below 3.5 K, once hot unless in town its best at 4 or more. , use 20 -50 , or straight 40,ive never had any real worries with this stuff.

Out of curiosity I checked the manual for any hints on sealing the OPRV, narry a word.

Last edited by gavin eisler; 01/05/18 8:54 pm.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: OPRV Leak Test [Re: DMadigan] #721219
01/05/18 11:08 pm
01/05/18 11:08 pm
Joined: May 2013
Posts: 4,663
Rotherham - S. Yorkshire
Allan Gill Online happy
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Allan Gill  Online Happy
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Joined: May 2013
Posts: 4,663
Rotherham - S. Yorkshire
I’ve never used anything more than the copper washer, to be honest I don’t know what depth it sits at and until now I have never considered it. But it works, there might be the tiniest leak but you’d never know lol.

However I do like the idea of diverting the oil blow by to the rockers, I have an oil filter and cooler on mine and I’m convinced that the two are giving enough back pressure to pump more oil to the rockers when I start riding it hard.

At least that way the oil then dumped into the sump would be returned to the tank instead of blowing out of the breather.


beerchug
Re: OPRV Leak Test [Re: DMadigan] #721224
01/05/18 11:49 pm
01/05/18 11:49 pm
Joined: Jan 2014
Posts: 3,422
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NickL Online content
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NickL  Online Content
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Allan, you should really tee into the oil return line after the filter for the rocker feed on a standard setup IMHO.

Directing the relief oil to the rocker gear is a plus in several ways, it blanks off the uncertain relief gallery,
Thereby ensuring no thread leakage.
It uses the pumped effort to cool/lube the head + rocker area rather than just returning it to tank.
It's easy to do.


Last edited by NickL; 01/05/18 11:52 pm.


Re: OPRV Leak Test [Re: DMadigan] #721333
01/07/18 12:55 am
01/07/18 12:55 am
Joined: May 2013
Posts: 4,663
Rotherham - S. Yorkshire
Allan Gill Online happy
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Allan Gill  Online Happy
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Joined: May 2013
Posts: 4,663
Rotherham - S. Yorkshire
I have thought about using an earlier bottom union without the rocker pipe take off, but the pipes are the smaller 5/16 type I believe? Would have hoped to have kept with the larger pipe size.

I have got a pre 68 oil tank in the garage with the pipe, originally designed for the rockers.

Interestingly my mates oil in frame uses the same oil filter and a permanent oil cooler (ie no thermostat) in note to a previous thread, his oil return is at a better rate at lower revs than mine. The fore mentioned thread was about a 68 also. Wonder if the oiling system was improved on the later cases?


beerchug
Re: OPRV Leak Test [Re: DMadigan] #721376
01/07/18 1:54 pm
01/07/18 1:54 pm
Joined: Aug 2001
Posts: 3,504
argyll. scotland, uk
gavin eisler Online content
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gavin eisler  Online Content
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Posts: 3,504
argyll. scotland, uk
Sorry for the thread drift, re rocker feed with return filter.
I used the 3 branch manifold , left a short stub of hose on the rocker spur and plugged it with an AMAL conc throttle stop screw. In the return line between filter and tank, the 3/8th hose steps down to 5/16 just before the adapter T. I fitted a 5/16" T , tapped the centre leg of the T to take a small length of screw which fitted the return pipe, this length of screw ( loctited into T with a turned down end to suit the rocker hose ID)was drilled centrally approx 3 mm diam to take the oil to the rockers ( hope this makes sense), had to shorten the small rigid pipe/coupling to the head to make it all fit between the carbs. Usefully the return line was enlarged to 3/8" from filter up to the T, stepping down to 5/16" 8mm, just before it. This gives a small but welcome increase in oil volume. My OIF now takes almost 5 pints to refill. Bought most of the pipe adapter fittings from vehicle wiring products.

You will need, one small screw to block pipe at manifold.
One off T piece spur tapped for drilled screw.i think I tapped 6mm threads
One off 3/8 to 5/16 stepped hose coupler
One screw drilled axially to fit 6 mm T spur, with a turned end to suit rocker hose.
Some clamps, various sizes to suit 3 sizes of oil line, 3/8 ID, 5/16 ID, and 3/16? ID, rocker line might be smaller , cant remember.
I made the drilled screw adaptor stub on a cheap pillar drill, a lathe would have been better.

I put it all together with the type of clamp that is non re usable, the sort with two small stub wings which get nipped to squeeze, these took up less room and dont have any catchy threaded ends to cut and scar.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
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