Classic British SparesKlempf British PartsBaxter CycleBritBike Sponsor SteadfastCyclesSRM EngineeringLucas Classic MotorcycleHepolite PistonsIndustrial tec supply

Upgrade your membership to: Premium Membership | Gold Membership | Life Membership | Vendor Membership | Site Sponsor Membership
Welcome to BritBike Forum!
Britbike forum logo
Member Spotlight
ricochetrider
ricochetrider
Pennsyltuckey
Posts: 11,481
Joined: May 2007
ShoutChat
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Previous Thread
Next Thread
Print Thread
Joined: Jan 2014
Posts: 761
Likes: 4
B
BigBars Offline OP
Britbike forum member
OP Offline
Britbike forum member
B
Joined: Jan 2014
Posts: 761
Likes: 4
Hi Folks, my oil pressure seems good but I've had a few cases where it has seemed a bit lower and then a bit later a bit higher again.

Yesterday I did a test run to check out the new primary rebuild and ran up two mountain passes and I think I have now understood the cause/effect relationship.

When climbing (higher throttle, more load and obviously front wheel higher than back) oil pressure seems to be lower than when coming back down, same revs and speed but this time lighter load and engine frequently under compression and obviously front wheel lower then rear (the passes are steep).

It was a mid 20 degree C day, the passes are narrow and windy so was not revving the crap out of it in either direction but would have been revving higher going up. I do have a thermostat in place so would expect oil temps to be similar in both directions.

When riding along on the flats, oil pressure is very much as per the "down" readings around 80 PSI above 3K but while climbing this can drop to around 70 PSI above 3k.

Not earth shattering pressures but I thought it was quite interesting and besides possible engine / oil temp differences I can't think of what would cause such a difference. Was trying to think about oil delivery in the crank under load or compression, bikes orientation, etc, but my head started to hurt.πŸ™„πŸ˜‰

Anyone ever noticed something similar?

Cheers


Couple pics of the run.

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]


3D TV: A format that lost a format war without even having an opponent.
Bikes: '69 T120 on average (1967 rolling frame and 1971 Bonnie engine) + '56 1/2 T110 on average (58 rolling frame - with 55 iron head engine) + 74 T150 Home model.
Support Your #1 BritBike Forum!

Check out British motorcycles for sale: British Motorcycles on e-Bay UK, British motorcycles on e-Bay North America
Joined: Aug 2001
Posts: 8,650
Likes: 77
T
Britbike forum member
Offline
Britbike forum member
T
Joined: Aug 2001
Posts: 8,650
Likes: 77
Maybe it’s the tilt angle of the gauge and its needle, rather than the bike.


Amateur Loctite enthusiast.
Joined: Feb 2008
Posts: 5,628
Likes: 243
Britbike forum member
Online Content
Britbike forum member
Joined: Feb 2008
Posts: 5,628
Likes: 243
Nice photos, Brett!

"I do have a thermostat in place so would expect oil temps to be similar in both directions."

Your statement is correct if the temperature of the oil going up or down are both at or above the thermostat opening temperature.
However what I suspect is happening here is that when going uphill you are producing more power and the oil temperature reaches the thermostat opening temperature so the oil temperature is controlled at that temperature or thereabouts.
But--when you are going downhill you need very little power and the convective cooling of the engine means that the oil temperature is below the opening temperature of the thermostat.
It may even be that both uphill and downhill that the oil temperature is below the thermostat opening temperature.
Either way the oil temperature going down hill is lower than the oil temperature going uphill.
As has been proven many times higher oil temperatures mean lower oil pressures and that is what you are seeing here.
The lower oil pressure is not a problem---- it is just that to get the correct oil flow through the oilways and bearings you need less pressure if the oil is hotter.
HTH

Joined: Dec 2004
Posts: 11,228
Likes: 134
Britbike forum member
Offline
Britbike forum member
Joined: Dec 2004
Posts: 11,228
Likes: 134
Or your OPRV is sticking.

Joined: Jan 2014
Posts: 761
Likes: 4
B
BigBars Offline OP
Britbike forum member
OP Offline
Britbike forum member
B
Joined: Jan 2014
Posts: 761
Likes: 4
Yeah, it really weird, thanks for all the input guys.

Yesterday I managed a few hours ride and came back on the highway when bike was fully warm, 15 minutes of around 5 to 6 k RPM oil pressure was rock steady at 80 PSI. Ambient temps again around mid 20s C. I would have though at these conditions oil temp would have been as hot as it gets. A real head scratcher


3D TV: A format that lost a format war without even having an opponent.
Bikes: '69 T120 on average (1967 rolling frame and 1971 Bonnie engine) + '56 1/2 T110 on average (58 rolling frame - with 55 iron head engine) + 74 T150 Home model.
Joined: Feb 2008
Posts: 5,628
Likes: 243
Britbike forum member
Online Content
Britbike forum member
Joined: Feb 2008
Posts: 5,628
Likes: 243
Brett--now you know why they call them "worry gages"!!!
You might like to disconnect the pressure gage, and concentrate on riding the bike and enjoying that wonderful scenery!

Joined: Jan 2014
Posts: 761
Likes: 4
B
BigBars Offline OP
Britbike forum member
OP Offline
Britbike forum member
B
Joined: Jan 2014
Posts: 761
Likes: 4
nah.... Never... I've got my Suzuki parallel twin for that πŸ˜‰


3D TV: A format that lost a format war without even having an opponent.
Bikes: '69 T120 on average (1967 rolling frame and 1971 Bonnie engine) + '56 1/2 T110 on average (58 rolling frame - with 55 iron head engine) + 74 T150 Home model.
Joined: Feb 2019
Posts: 477
Likes: 190
S
Britbike forum member
Offline
Britbike forum member
S
Joined: Feb 2019
Posts: 477
Likes: 190
Originally Posted by BigBars
Yesterday I managed a few hours ride and came back on the highway when bike was fully warm, 15 minutes of around 5 to 6 k RPM oil pressure was rock steady at 80 PSI.
I don't think you have a thing to worry about, at least with your oil pressure.

I also think you need to add a oil temp gauge to your instrumentation portfolio. A cooking thermometer dipped in the oil tank works just fine and isn't costly.

Oil is notoriously slow to heat up. It takes my triple around 30 miles of 70-80 MPH freeway riding for my oil temp to get above 180 with my cooler blocked off with cardboard..

Based on this experience, your thermostat may not even be opening yet but you won't know without checking the temps, even really basic stuff like feeling if your oil cooler feed hose fitting is warm to the touch. If it's cold, the thermostat hasn't opened yet.

My oil pressure finally drops down to 65psi at around 5500rpm when the oil temp gets above 180. Otherwise it stays up around 75- 80psi or higher when the oil is colder.

Joined: Feb 2008
Posts: 5,628
Likes: 243
Britbike forum member
Online Content
Britbike forum member
Joined: Feb 2008
Posts: 5,628
Likes: 243
When developing the oil cooler "back in the day" we reckoned it took 10-15 minutes riding flat out on a closed test track to get to thermal equilibrium.
Thermal equilibrium was judged by steady oil temperatures with the bikes oil system fully instrumented with thermocouples.
You do not often get true thermal equilibrium on the open road---you get baulked even on the autobahn.

Joined: Feb 2019
Posts: 477
Likes: 190
S
Britbike forum member
Offline
Britbike forum member
S
Joined: Feb 2019
Posts: 477
Likes: 190
Originally Posted by Tridentman
......we reckoned it took 10-15 minutes riding flat out on a closed test track to get to thermal equilibrium......
So, that was about 15 minutes at 120-125 MPH? Some among us are hoping for a resounding yes!
But whatever speed, the best part is you got paid to do it.

Joined: Feb 2008
Posts: 5,628
Likes: 243
Britbike forum member
Online Content
Britbike forum member
Joined: Feb 2008
Posts: 5,628
Likes: 243
Well Stuart---here is your resounding YES!
The MIRA test track was (is?) triangular in shape with banking at the three turns.
The speed was about 125 mph on the straights and it dropped to about 100 mph on the banking---due to extra load on the tires due to centrifugal force with the suspension bottoming out'
And another yes--it was good getting paid for it!
There were a couple of negatives as well---
At the top of the banking were steel posts spaced about ten feet apart with a wire rope strung between the posts.
The intent was to restrain a car if it went up to the top of the banking.
As I was going around on the banking I couldn't help thinking that the wire rope looked a bit like a cheese cutter and that is what it would do to me if I got to the top of the banking.
Fortunately that didn't happen--otherwise I probably wouldn't be writing this!
The other negative did happen.
After about ten minutes flat out I was coming off the banking and without thinking, based purely on instinct I pulled in the clutch just as there was an almighty bang and the drive side rod burst through the crankcase. Fortunately I stayed on the bike.
It was about 3 p.m. so I called Alan Barrett, the Meriden development shop foreman and told him what had happened.
" Don't worry about it" he said "they do that sometimes"
"What time can you get the bike back to Meriden?"
We got the bike back to Meriden at about 5 p.m. and Alan said" You can pick it up at 9 a.m. tomorrow morning---I have a fitter who will be working on it all night to put a new engine in"
So we picked up the bike the next morning, complete with new engine, went straight to MIRA and carried on testing.
Breaking in the new engine consisted of a couple of laps varying the speed and load of the engine so that by the end of the second lap it was being revved up to about 7K rpm.
Happy Days!

Joined: Oct 2008
Posts: 7,168
Likes: 134
Britbike forum member
Offline
Britbike forum member
Joined: Oct 2008
Posts: 7,168
Likes: 134
We have that 'cheese cutter' barrier next to some sections of the interstate highway, usually on the median side of the road.
I wish I'd had someone to install a spare engine when my first Trident went bang with the drive side rod poking out of the case. laughing


Knowledge speaks. Wisdom listens.

72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"
92 BMW K100rs "Gustav"

Moderated by  Tridentman 

Link Copied to Clipboard
Job CycleBritish Cycle SupplyMorries PlaceKlempf British PartsPodtronicVintage MagazineBSA Unit SinglesBritBike SponsorBritish Tools & FastenersBritBike SponsorBritBike Sponsor






Β© 1996-2021 britbike.com
Powered by UBB.threads™ PHP Forum Software 7.7.5