Bonneville America Forums Forums Technical Forums General Tech Low oil pressure?

Took her out for a spin today. After riding for a bit, I could swear that I was getting less engine braking when downshifting, but I could be imagining things. So I'm stopped at a light and my oil pressure at idle was down below 10psi. I'm letting it cool down before I peek for leaks, but the banjo fitting on the gauge was dry.

Anyone else with Brent's gauge know their pressure at idle when warm?

Clutch not slipping? I have almost 15,000 on the clock and always downshift when slowing. Never to the point of over-revving, but always when slowing or stopping. Detected clutch slipping the other day when in 5th gear about 60 mph or so if I hit throttle hard.
Don't know if oil pressure would matter, engine braking comes from compression.

I think the engine braking may just be a figment of my imagination, but I wouldn't doubt it if my clutch needed adjusting or new springs... And I certainly wouldn't doubt the braking/pressure to be completely independant either.

Benny, my oil pressure gauge (same kit) is reading around 20 to 22 psi at idle. That's after a 32 mile commute, and my idle is a little on the slow side at the moment.

Interesting.... Mine was definitely low then. I suppose it is possible my bike will always run a little low, but below 10 seens way low, no?

Does seem odd, especially since the idiot light is supposed to go off at 7psi. Mine seems to have "worn in" a bit, with regards to pressure at idle. Right after install, the gauge would read high 20's up to 30psi at idle after fully warmed up, and the gauge gradually read slighly lower as time went on, at hot idle. Still pegging 80psi on the highway, even hot.

Yeah it still zips right up as I twist the throttle. I'll pay more attention to the high side of the range later today and see what's up.

Benny, to be on the safe side until you figure out what's up increase your idle rpm to raise up the pressure a little.

Benny,
I wonder if this is linked to your temp issue. Maybe your oil pump isn't working 100%. Also, the nylon oil pump gear could be slipping or missing a tooth. If the oil isn't pumping fast enough it could lead to higher temps.

Good point. I think the only way to tell on that is some "major surgery" tho right? Aside from draining the oil first, which side cover would I pull off to check that? Maybe it is time to get some brass gears... I REALLY don't want to tear my motor down.... I am thinking some more testing first, like putting the other gauge back on to see the difference, that sort of thing.

Benny,
Mine reads <20psi if the idle is below ~900rpm and the motor is warmed up. When cold and started up (with choke/enricher engaged) it reads ~ 50psi. (as the oil heats up, it thins out, viscosiy drops = pressure drops)
I set my idle so the pressure is about 30+ AFTER warmup.
Normal, turn your idle up a pubimeter.
BUT...be sure all is tight!

And also the type oil you are using could cause differences as well. As in 10-40, 15-50, or 20-50. Hard to really compare readings from one bike to the next unless you're running the same weight oil at comparable temps.

Both good points. I am running 15W50 and I suppose it is possible that the DS tach isn't 100% accurate so my idle is in fact low... Will adjust. I had lowered it once I installed the tach cause I wasidling north of 1100rpm.

Benny, with my idle around 1150 or so, I showed about 24 psi this morning after my commute. If you want to inspect your oil pump gears, all you have to do is pull the clutch cover (LH cover), and the gears can be inspected with the clutch completely in place. FWIW, running amsoil 10W/40.

So I'm not too up on my oil weights... is yours heavier than mine or thinner? I am going to bump my idle when I get a chance, should get some ridable weather this weekend.

Your oil is thicker than mine (more viscous), so I would think you'd be getting slightly higher pressure than mine, because mine would "thin" out a bit more once it's hot.

Benny,
Seeing 10psi on a fully warmed engine at idle is not by itself a reason to worry. However if you continue to see a decline (ie. next week it reads 5psi)that would indicate a potential issue. As the other posters correctly point out worn gears, oil viscocity, temperature (ambient and oil)are variables that play into the equation. Check with any HD rider and they will tell you low psi at idle is a way of life. A loping idle turns all accessories slower. I suggest not seeing a consistent low and high reading is the point of worry. BTW thanks (sorry) for this prime example of the beauty of this gadget being in your face. You can call me if you would like to discuss this further.
thanks
tod

Thanks Tod. Thinking about it more and more, I'm thinking that consistency is what I should be after, and using the gauge as a point of reference, not truly an absolute measurement. I am going to take it out, warm it up for a nice ride (close to home) and see if it is still low. Then I'm going to up the idle a bit and see how it goes. I will also be checking my oil level now that it has sat for a couple days. I would REALLY worry if it DIDN'T shoot up when I blipped the throttle.

You know I have been thinking. Asthetically I actualy prefer the location down on the motor next to the temp gauge, looks cool. But functionally having it up on the bars, especially if you are worried about pressure to begin with, is nice.

Repeat after me: "Function over Form, Function over Form" I came pretty close to buying the BP kit, but gladly held off when Brent came out with this set-up. There's no comparison to having the read-out right in front of your face.

Benny,
Two gauges would put you over the top.
You want me to look at a triple bajo bolt?

Can never have too many gauges Altho redundant gauges are a little over the top.

That is function! Already got bit once by nylon, I'll put my trust in metal this time around.

I wonder how worn gears hould make the poil pump operate just a smidge too slow? With my temp issues in the past, I wonder if I have a partially blocked oil passage somewhere... Altho without completely removing the cylinders, I doubt I will be able to find anything.

Benny,
This will sound stupid but think of your oil pump as an electric egg beater.
Worn pump gears will decrease the amount of oil that can be moved. The gears push fluid by inter-meshing together compressing the oil on the face of the gear teeth. As the tolerances increase (wear) between the gears lowers the amount of oil that they can move. I'm gonna get another beer now.

Oh ok, so the gears everyone talks about do the actual pumping! I had assumed that the gears where DRIVING a pump of some sort. Now it makes sense.

just a thought, but maybe a lousy, defective or slightly clogged oil filter? might try a new filter since only a small amoubt of oil is lose removing the filter so you wouldn't have to change the oil.

Well I just changed the oil and filter, so doubtful, but I may check it for obstructions.

The oil pumps are gerotor style pumps, driven by nylon gears. These pumps are relatively bullet-proof, until you try to wedge something ugly through them. Same goes for the nylon gears. Everything wears over time, but with normal maintenance and barring a catastrophic failure, they should last a loooong time.

No, you're right, the gears drive the pumps that do the pumping. The gears and pumps are completely accessible for Removal and Replacement once the clutch cover and clutch assembly are removed.

Anybody remember the nylon timing gear used in cars during the late 70's? They would last 100,00 miles sometimes. They did that to keep the noise down. They worked until they wore then when you tried to set the timing it would not hold. The mark shown by the timing light wandered back and forth like drunk after a bender.

Ben,
Another thing to check woul be the oil screen. It is accessable by (i believe...) removing the oil pan (requires pulling pipes and probably headers too). There is a large nylon bowl type assembly with a stainless screen in the bottom of the part. It feeds from the oil sump into the oil pumps. If there is a lot of slime in yours, it could impeed the oil flow abit too. A long shot, but since seeing all the crud and bits in Jaymos when we had it apart, I would not rule it out. A winter project for sure. You would probably need to lift the bike and support it then remove the jack for lots of working room underneath. Not an easy job, but you could do it, it's just a lot of little bits to get out of the way first.
There are also three small oil feed lines in the motor, you saw the one on top of the cams right? There are two more like that and I would think a very small amount of gasket material/RTV/Dirt could easily clog them by 50% at least. Look through the shop manual and you'll find them. One of them is also on the nylon screen res I mention above. I beleive the last one was behind the right hand shifter cover, down and behind the magneto cover, oposite the shifter arm.

OK thanks guys.

But I am still back to being a bit confused about how worn gears could slow the pump. They are either meshed and turning together, or slipping... one of the other, right? So the pump is either turning or not. Unfortunately I am loosing full access to a garage real soon I'll have to gauge how much space I'll have to work on it. I am also thinking I need to take the bike out and re-adjust the pilot screws for a good idle and go from there. Hopefulyl tweaking the idle/carbs will improve things. Otherwise, the slime/gunk theory is high on my probablility list, and my PITA list.

Benny,

Like everyone says check the simpe first and go from there. Have you pulled the Oil Pressure Gage itself and checked the pick-up to make sure it is clean.

John

I haven't completely disconnected it, just looked for leaks.

Meant to post earlier.... Went out for about an hour of riding today, two up. Met up with Keith (kars) for a little tire kickin, always good to meet another member! Anyway, while I was warming up the bike, I jacked up the idle a quarter turn or so. So now I'm idling above 1k, but not much. PRessure at idle was about 15psi, pulling about 70psi with a decent handful of throttle. Sound about right?

What kind of ambient temps? The lowest I've seen at idle has been about 22 psi, and that was in the mid to high 80's in the afternoon.

Maybe it was 25 psi.... Like I said, we were two-up so I was probably too distracted... Ambient temps were in the 50's at best.

25 wouldn't be bad at all. I had over 30 psi at idle when I came in this morning, 47 degrees, but my idle is a tad too fast at the moment.

I'll have to take it for another spin