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Low Oil Pressure 1968 TR6c #732076
04/16/18 4:54 pm
04/16/18 4:54 pm
Joined: Mar 2018
Posts: 8
Baytown, TX, USA
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Gary Walentoski Offline OP
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Baytown, TX, USA
Having trouble with low oil pressure on my 1968 TR6c 650. The engine was completely rebuilt last year by a shop down here near Houston. All seemed well after the rebuild and I put about 350 miles on it. I took it back to the rebuilder to have him inspect everything, change oil, and to have Boyer ignition added in lieu of the points. Got the bike back and noticed I had an oil light on after the engine was hot and at idle, after a 10 mile ride. I fitted a gauge and found I had 20 PSI cold and 7 PSI at hot & idle. I took the bike back to the shop and they've checked the screens, replaced the timing cover crank seal (Pioneer), replaced the new OPRV with another new one, checked the new oil pump, made sure that timed tappets were fitted. All this made no difference to the oil pressure. The oil is correct grade. Outside of the big end bearings, what else is left? I'm concerned that the pressure is not nearly high enough when it's cold. The shop is stumped at this point and I'm ready to look elsewhere for help, since riding season is here!

THANKS!

Gary

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Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732077
04/16/18 5:00 pm
04/16/18 5:00 pm
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scotland
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There is probably a slightly big big-end clearance.


Amateur Loctite enthusiast.
Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732088
04/16/18 6:41 pm
04/16/18 6:41 pm
Joined: Mar 2018
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Baytown, TX, USA
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Gary Walentoski Offline OP
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TT, That is what I'm thinking, but I want to make sure that maybe they did not miss something else.

Thank you!

Gary

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732101
04/16/18 8:27 pm
04/16/18 8:27 pm
Joined: Nov 2012
Posts: 899
Isle of Wight, UK
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koan58 Online content
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The most obvious thing to check is the oil seal in the timing cover, then the feed side of the pump (ball seating), and that the OPRV is working freeely.
After these, if the pressure is still very low, can you not hear any knocking from the engine?
If the big ends were worn enough to give 20psi cold, I'd expect them to be saying hello to you very soon.
Hopefully, this is a pump or seal problem, don't tear it down just yet.

Re: Low Oil Pressure 1968 TR6c [Re: koan58] #732106
04/16/18 9:32 pm
04/16/18 9:32 pm
Joined: Mar 2018
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Baytown, TX, USA
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Gary Walentoski Offline OP
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The engine was running fine, no knocking at all. I did not trust the low pressure light, I assumed the sending unit was bad, so I fitted the gauge. OPRV and pump seem fine (old units were refitted, to be sure, with no change). Seal was replaced, just in case. Still no joy.

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732109
04/16/18 10:06 pm
04/16/18 10:06 pm
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Isle of Wight, UK
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koan58 Online content
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I'm not familiar with the units, is the feed to the exhaust tappet block still necessary? If you block that off, what difference does it make to the oil pressure?
The pressures you have been reporting are not adequate for reasonable engine life, so it needs to be sorted.

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732117
04/16/18 11:07 pm
04/16/18 11:07 pm
Joined: Sep 2001
Posts: 743
Great Southern Land
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Take the head and barrels off.............then grab a piston and see what movement you have. Up and down or rocking side to side = big end issues.....note that there will be a small amount of sliding side to side movement, this is OK.

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732134
04/17/18 2:28 am
04/17/18 2:28 am
Joined: Feb 2014
Posts: 1,256
Lancaster, California
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How about taking the timing cover off and seeing if the oil feed seal is installed the correct way? It could be backwards or it could be inverted? Everyone always wants to jump to the big end.... troubleshoot other areas first

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732148
04/17/18 7:17 am
04/17/18 7:17 am
Joined: Jan 2017
Posts: 639
Pleasant Hill, California USA
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TR7RVMan Offline
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Hi Gary, That's too bad.

To be clear, it was ok so far as you know until shop changed oil? Is that correct?

Exactly what oil did it have before during break in? Exactly what oil does it have now?

7 psi might be on the cusp of turning on the light. It could have been nearly too low prior to oil change but didn't turn on light with break in oil?? The new oil might be just enough to push it under the limit you were almost at??

Sounds to me like your bases have been pretty well covered other than the tappets. You say they are correct. How do you know?

Generally speaking a smoking hot motor after 2 hrs. riding 82f day, will idle about 17-20# at about 900-1000 rpm. Even 50 rpm more will raise oil pressure a few PSI hot.The type oil & RPM will effect pressure. Raising idle to 1300 will often add 15# on gauge. Reving hot 4000 RPM will be about 70#. So you are indeed too low.

When you say timed tappets, which timed tappets? Early with wide grooves or late with narrow grooves?

Are you running tappet feed restrictor or hollow dowel? A mistake here very well could account for this much loss.

Ran into this recently on motor overhaul while doing ,69 Bonnie motor. Removing the restrictor that should have been a hollow dowel on '69 bonnie lowered idle pressure about 12-15#. Prior owner installed it at some point. Why?? I always wondered why pressure was so high at idle. It also restricted bore to PRV so 4000 rpm hot was 90#. Had correct narrow groove tappets. Changing to correct hollow dowel correct pressure idle & reving. This bike has gauge installed on it. Original oil pump & PRV were reused.

The rod clearance was .0015" using plastigauge. Has correct for this year narrow groove timed tappets. Hollow dowel. The idle pressure hot is 17-20. Interestingly break in oil was Torco TBO 40w. After 400 miles changed to Mobil1 20-50 v-twin. On pressure increased by a good 2# hot. I expected a loss as V-twin feels thinner coming out of bottle, but I guess not hot.

Back to your bike, I expect the shop would have verified correct seal installation when they replaced it again. I hope they tested oil pump like manual says pulling plungers & watching for oil drop in ports. This test is very effective. I have a repro pump nearly new that failed the test & gave low oil pressure. The ball seat is out of round & not sealing well. Plainly showed fail during the test.

With timing cover off you can test PRV for being stuck open by pumping oil into front dowel. If valve is stuck open oil will readily exit the bleed off bore that points towards the exhaust cam gear. More often the timing cover is not off, so you must do careful inspection of PRV. If at all possible we want to actually see the problem.

I remove OPR valve & very carefully look at plunger position to see if it's stuck open. Even if it's stuck partially open 99% of the time you can see it's stuck.

A broken spring in valve can look like stuck open. We'll take apart later & inspect spring visually in any case.

If dirt or something gets beside piston or between piston & port edge it can jam piston open. A broken spring will allow piston to move back & uncover port. .

Occasionally a stuck open piston will free itself as you remove valve. In this case you won't know what happened. 99% of time a stuck valve will stay stuck. Usually a metal chip or gasket chip is seen holding piston back. In every case I separate valve, remove piston & verify no dirt is behind piston. You want to visually inspect spring anyway. Again try to see a fault if there is one.

Since you tried a known good valve, we'll rule PRV out, but now you know for next time.

I've tried to get a feel of pumping oil into tappet feed dowel to see if I could tell if had wrong tappets. I could not get a feel for that. So visual inspection is what I have to do, which means pulling cyl & tappets. Cly will have to come off to split cases anyway so check this before removing motor.

I've tried to pump oil into crank feed bore & see if I could feel for worn bearings by feeling if oil pumped in too easy. I could not.

I have pumped oil into crank feed & watched oil exit rod bearigs & see if I could tell wear that way. I could not.

I cannot feel if a rod bearing has .001 or .003" play. I doubt you can either. If bearing is wasted & knocking bad you can feel that if you have practice.

I have to measure bearing clearance with micrometer & bore gauge or use plastigauge. That is really the only way.

Another source of low oil pressure in leaks at the sludge tube plug & possibly the flywheel bolt. This should have been checked before assembly.

I always pump oil into crank hard & visually check bolt, plug, crank oil way plug for any signs of leakage after assembly with crank on bench. There should be none.

Be sure to pump oil into crank with rods still on & test for leaks before you remove rods. Look for oil coming out anywhere it shouldn't. Like a crack in crank even.

Since you don't have a base line with pressure gauge after overhaul, you don't really know what happened. It is most important on teardown everything that could effect pressure is examined most carefully.

I most strongly recommend using plastigauge to measure actual rod bearing clearance. Make sure the plastigauge is not aged. It should still be soft & pliable, not hard/brittle or it doesn't read accurately.

No guess work, you need to find the fault(s). Then correct all faults & verify all is well at each step during assembly.

Good luck on your journey. Hope the solution is readily found.
Don






1973 Tiger 750
Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732149
04/17/18 7:18 am
04/17/18 7:18 am
Joined: Jun 2002
Posts: 10,264
Scotland
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Stuart Offline
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Hi Gary,

Originally Posted by Gary Walentoski
I fitted a gauge and found I had 20 PSI cold and 7 PSI at hot & idle.

What's the pressure above about 3,500 rpm when hot?

Regards,

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732164
04/17/18 11:51 am
04/17/18 11:51 am
Joined: Sep 2008
Posts: 972
Skudeneshavn Norway
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Stein Roger Offline

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Skudeneshavn Norway
Lot's of good suggestions already, perhaps no need for more, but I have a couple anyway:

A friend of mine, not too familiar with these plunger pumps, asked me the same question. Looking over the pump, I found the feed plunger ball valve seat had never been cut. This was also on a ca 68 engine, and the bike had seen some use in those years. Must have run with low oil pressure it's whole life. I cut a new seat and all was fine. My point is, the seat may look good, but may still be damaged. Another friend has a ball welded to a rod that he grinds the seats with. I haven't done that yet but will if I have to.

Other suggestion, I recently had issues with oil seeping from the exhaust tappet guide block on a T140. Since it was otherwise oil tight and running great, I cheated a little by plugging the tappet oil feed drill-way behind the OPRV. It's easily done by removing the timing cover and OPRV. I made a solid dowel of ca 5,1 mm in diameter and 12 mm long, and pushed it in with a suitable drift. I cleaned as well as I could and used a spot of Loctite on it, but also peened some aluminium over it.
I got the result I looked for, no leak, but must also have gained a few psi more in oil pressure. I haven't measured the OP but the warning light extinguishes sooner and stays out for longer, when kicking the engine over.

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732171
04/17/18 1:30 pm
04/17/18 1:30 pm
Joined: Dec 2004
Posts: 9,876
Scotland
kommando Online content
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Its ok to block the tappet oil feed off on any 650/750 with Nitrided cams, but a 68 did not have nitrided fitted at the factory so unless you know the cams have been changed to nitrided then leave the tappet oil feed in place but in the correct configuration for a 68.

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732174
04/17/18 2:22 pm
04/17/18 2:22 pm
Joined: Sep 2008
Posts: 972
Skudeneshavn Norway
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Stein Roger Offline

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Good catch kommando, thanks.

Re: Low Oil Pressure 1968 TR6c [Re: Stuart] #732197
04/17/18 4:58 pm
04/17/18 4:58 pm
Joined: Mar 2018
Posts: 8
Baytown, TX, USA
G
Gary Walentoski Offline OP
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Baytown, TX, USA
Stuart, The best the pressure was maybe 10 PSI at higher RPM. I noticed the longer the engine is run, the lower the pressure goes. I'm assuming that had to do with oil thinning at temperature.
Gary


Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732199
04/17/18 5:06 pm
04/17/18 5:06 pm
Joined: Mar 2018
Posts: 8
Baytown, TX, USA
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Gary Walentoski Offline OP
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Baytown, TX, USA
A lot of good suggestions from everyone. Thank you! I'm making a list for the engine guy and I'll see him in the next day or so. I want this fixed. I enjoy this bike way too much and I want it back on the road SOON!
Gary

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #732200
04/17/18 5:10 pm
04/17/18 5:10 pm
Joined: Nov 2012
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Isle of Wight, UK
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koan58 Online content
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Pretty much all the possibillities from the feed side of the pump have been suggested in previous posts (barring something truly exceptional like a breaking crank etc).
If you are satisfied that all the obvious pre-teardown options suggested so far are not responsible, and have double checked with another gauge that the situation is definitely real (or checked your gauge in some other way), I have one other long-shot suggestion worth a try before teardown.

With a normal amount of cold oil in the tank, remove the oil pump. Is there a steady flow of oil from the supply port in the crankcase that continues for several minutes?
What I'm getting at is that if the pump can't receive enough oil in the first place, it will not deliver the necessary flow to the crank. This could be due to a restriction caused by a gunged up gauze in the tank or maybe a sliver of rubber pipe somewhere in the feed to the pump.
Something that I've experienced myself, that showed up as I was cruising along a motorway, was gradually diminishing oil pressure. From the usual hot oil 60 or so psi, it dropped to ~40 over a few miles (I'm sure you can imagine that my attention was not on the road, but the gauge). Expecting the worst, I slowed to ~45 mph to tickle it along gently to the next service stop, pressure now frighteningly low, 15 and falling.
The guy in the petrol station couldn't have been more helpful, as my investigation was a very messy oily one, I needed catch trays (he got some plastic food containers from a bin), frequent hand washing (gave me a bottle of liquid soap to use with an outside tap) and a whole blue roll. He was only 20 something, ran a 70's CB500/4, and loved older bikes, thanks be to some of the oft criticised younger generation!

After getting this organised, I returned to the bike, to find a significant pool of oil on the ground. This was unusual, and it reminded me of my friend's comment that morning of drips on her garage floor. So before taking the timing cover off, I just lay next to the bike with a ciggy, watching. The drips were from the bottom of the crankcase (pre-unit). So I started from there with the blue roll and found that the oil was leaking from a split in the feed pipe from the tank.
Only then did I understand that the draw of the pump was taking in what was most easily available to it (air), and as the split developed, air became an increasing part of the mix. I suspect the crank survived because of the end feed/centrifuge nature of the design, but I wouldn't want to push that too far!

Ended up blocking the oil tank outlet with blue roll, so I could remove the pipe and clean it with petrol, allowing insulating tape to stick, and several hundred more miles before getting home and sorting it properly.

Please forgive such a lengthy story, the essence of it is that the supply to the pump may be worth checking as well.

Re: Low Oil Pressure 1968 TR6c [Re: koan58] #732204
04/17/18 6:17 pm
04/17/18 6:17 pm
Joined: Mar 2018
Posts: 8
Baytown, TX, USA
G
Gary Walentoski Offline OP
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Baytown, TX, USA
koan, Good story and worth looking into. The engine was rebuilt as I had holed a piston. Tank, hoses, lines, screens were washed out multiple times and blown dry. That said, everything has been open and that means something may have found its way into the tank or lines. I certainly will make sure we have a good flow.
Thank you.
Gary

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #753936
10/25/18 3:25 am
10/25/18 3:25 am
Joined: Oct 2009
Posts: 297
Diamond Springs, Kalifornia
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How does this end? Or has it?


Michael

currently owned by a 72 T120R
'02 Sprint ST
maker of plunger conversion jig
Re: Low Oil Pressure 1968 TR6c [Re: Buckshot1] #754526
10/30/18 1:56 am
10/30/18 1:56 am
Joined: Mar 2018
Posts: 8
Baytown, TX, USA
G
Gary Walentoski Offline OP
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Buckshot1,

Interesting you should ask...
The engine was taken completely down to the crank by the re-builder. It's supposed to be back together and he's putting a few miles on it to make sure all is good. I'm going over there Thursday to get the rest of the story and to hopefully pick it up. Since the temps are out of the 90's here finally, we're into some good biking weather and I'm more than ready (hope the Trophy is too.)

GaryW

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #761059
12/31/18 10:22 pm
12/31/18 10:22 pm
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Posts: 8
Baytown, TX, USA
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Gary Walentoski Offline OP
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UPDATE!: Well, after 11+ months, I picked the bike up the end of last week; at least no charge to me to get it rectified. What I know: Cold oil pressure is now 65 PSI. Hot idling oil pressure is 35 PSI. Going down the road I'm seeing about 50-55 PSI. The re-builder was sketchy about the cause, only to see its was easily missed and one to chalk up for the future. I'm thinking it was timed tappets (maybe wide groove fitted when it needed narrow), as John Healy detailed in the Autumn issue of Vintage Bike, but I'm only guessing. I know the guy took it all the way down to the crank and checked for cracking but all was good.

Now if the rain would stop, I can get a little riding done to make up some for last year. Happy New Year to y'all!

Gary W

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #761158
01/01/19 6:34 pm
01/01/19 6:34 pm
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Posts: 268
Monclova
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I'm glad its better, but after a fresh rebuild just doesn't sound exactly right. It'll get down the road with 50 to 55 but certainly should be running at 70 to 80 pounds when hot. This is with 20 50 Castrol or a good substitute. 35 at idle seems high unless you have the idle turned way up. Should be about 20 to 25. An old trick is to stretch the OPRV spring out to bring up the oil pressure. However, this usually only works until the engine is completely warmed up and then no matter how much yo stretch the spring out the oil pressure will fall to whatever the journals will allow for. Did the crankshaft get turned? I do a lot of triumphs and especially BSA's engines, and I wish I had a dollar for every time I tore one down that had low oil pressure problems that were supposedly rebuilt. Happens more with A65's than 650 Triumphs but it does happen. The crank must be in specs, if its out a little and the crank grinder ( that is not familiar with British Twins) Says that'll be close enough, its not, refresh the crank. Youl be happier and know the bottom end is correct and to specs. I'm not saying the other items mentioned in this thread are to be shuffled to the side, no, but do you even know if the crank was turned? Just my two cents, get that baby good and hot and see what kind of oil pressure you have, if it continually falls then Id say the journals are suspect. I know some on this page will say 50 55 pounds is good enough, but after a fresh rebuild it should be more. I have a 650 I rebuilt 10 years ago and was my daily rider up until last year that maintains a constant 80 pounds when hot all day long. Hope it all works out.

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #761194
01/01/19 11:49 pm
01/01/19 11:49 pm
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Isle of Wight, UK
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koan58 Online content
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I'd agree that a crank with as new clearances and a decent pump should shoot to perhaps 85psi (my old Smiths gauge bounces off the stop and back to about there) starting from cold, but this will moderate over 20 minutes of riding to about 70psi running, when fully warmed (could be an hour or more) idle may be 15psi, up to ~50psi at 3.5K. If you're seeing above ~60psi hot at high revs then I think the OPRV isn't doing its job. That is roughly the design pressure for the system.

Mine is a pre-unit, when it just had its bronze bush "sealing" the oil supply to the crank, hot oil pressure would be maybe 30psi at 3.5K and barely observable at idling.
On a Triumph twin oil pressure is really only a vague indicator of lube health. If there is any significant pressure at all, it means all the cavities between pump and bigends are filled with oil. As long as the crank is fully filled with oil most of the bigend lubing is achieved by the centrifugal action of the crank itself.

Your reported pressures do sound slightly on the low side, but not so much that I'd tear it back down again until it is absolutely necessary, which may be many years away. Pump and oil seal condition (and crank nose) can contribute, and worth checking out first.
If it doesn't knock, ride and enjoy!

I wouldn't advise bending OPRV springs, once they're bent they're wrecked, it's clutching at silly straws IMHO. We wouldn't do it with valve springs would we?

Re: Low Oil Pressure 1968 TR6c [Re: Gary Walentoski] #761210
01/02/19 3:34 am
01/02/19 3:34 am
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Pleasant Hill, California USA
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TR7RVMan Offline
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Hi Gary, I expect if it had the wrong tappets he would not have done a full tear down. With all that was tried prior it sounds like too much big end bearing clearance, or... a leak at sludge trap plug

Regarding pressure changes by stretching PRV spring, it cannot raise pressure at lower RPM, only when pressure would be above the opening pressure would any change be seen.

The pressures you report seem plausible. A few questions.

Exactly what oil is in bike now?

When you did hot test, how long was motor running? Generally it will take at least 20-30 miles to fully warm motor.

What RPM was the idle when idle pressure was taken. As I'm sure you saw small rpm change at idle gives large changes in pressure.

What road speed was the 50-55# seen? I find many motors tend to be about 50 [email protected] 50 mph, with pressure about 70# at 70 mph. This is with heat soaked motor Mobil1 v-twin20-50 oil. Many motors will be 17-22# at 1000-1050 rpm heat soaked motor, again after 20-30 miles. More miles needed to heat soak @ 70f or lower. The ambient I'm talking about is 80-90f after 60 miles continuous running.

Even .0005 clearance change on big end will show in oil pressure. Even a tiny fault in oil pump check balls will lower pressure. Worn drive block will also lower pressure.

I wish I had more experience with pressure value at different clearances, but the figures you say sound like .0013-.0015" . Again I don't have many motors to compare, just a few. I experience is you'll be good with the pressures you state. Also is the gauge accurate??? That's an unknown for most of us as we only have 1 gauge.

I would feel very comfortable with your idle pressure if motor is heat soaked. The high rpm pressure is ok if heat soaked also. Higher is fine too. If bearing clearance is too little the oil pressure will read higher, but the effective oil flow through bearing clearance is retarded by the tight clearance & the low flow cannot take the heat away as it should.

A stronger PRV spring will raise pressure at speed if.... the oil pump can put out enough volume. If pump lacks volume, or... oil is lost due to excessive clearance or some other reason the stronger spring will not effect a change. I can say from personal experience if clearances & other things are ok, blocking off tappet feed will increase pressure by about 10-25# depending on RPM. Of course this removes the extra lube to tappets which might not be a good plan.

On a side note I found straight 40w Torco TBO oil was much thicker cold than V-twin 20-50, however heat soaked the v-twin gave a least 3 psi more pressure at idle, showing the multi grade really can retard heat thinning. So oil type can have an influence on pressure more than I would have thought.
Don


1973 Tiger 750

Moderated by  John Healy 

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