Hard Braking

[BAMBY]

Occasionally, I make a couple high speed passes on a backroad around my area, where nobody is around to care...
So its long enough to get it up to 100, but then you have to brake pretty good to slow down...

I noticed that upon REALLY hard braking (like if i applied the front brake harder, it would lock the front wheel) that sometimes my oil pressure light comes on...
the bike is really nosed down, because of the braking, and once i saw the light come on, i let off the brake right away, so i didnt notice any difference in rpm, nor engine performance or anything else...

Anybody else experience this, or have ideas to explain this?
BAMBY

[Munkey]

If you ever pull the oil pan off your bike, you'll see why this happens. The pickup and screen for the oil pump is closer to the rear of the engine. When you are braking this hard, the oil in the pan all moves forward from the G forces. This causes the oil pump to suck air and temporarily drops your oil pressure.

[JB1290]

Could that mean the bike is low on oil?

[BAMBY]

Well, Munkey, i guess we think alike... because that was what i suspected when i looked at some pictures of the pickup/pan etc...
But i still dont like the thought of it suckin air for a second or two... it makes me feel bad for the bearings in my engine that get starved for that moment. 

and JB1290- i check my oil regularly, so i know it is full- but that was my first worry, until i double checked it...

Has anyone actually had this happen to them though?

[LOKi]

Yes. My light comes on in really hard braking. There might be a drop in oil pressure but I'm pretty sure the parts are still getting oil. No worse than start up anyway. How long can you realistically hold that G-Force? It only takes a few seconds to come down from 100 all the way to 0. Under more realistic conditions from 80 to 0.

[Laminar]

Yes. My light comes on in really hard braking. There might be a drop in oil pressure but I'm pretty sure the parts are still getting oil.

What leads you to believe this?

It only takes a few seconds to come down from 100 all the way to 0. Under more realistic conditions from 80 to 0.

It only takes a few seconds of metal-on-metal contact to score bearing surfaces.

[ariwhiteboy]

Could the low oil pressure also be caused by a combination of letting off the throttle hard braking dropping the revs enough? 

[OhCrap]

I don't think I ever rode a bike with an oil light that didn't came on under hard breaking. I wouldn't worry about it to much, just don't make the light go on like this to often 

[happycommuter]

I've never looked at the instruments while emergency braking.  I'll have to try this.

Obviously no surfaces are going bone dry in this ephemeral moment, and only a bonehead is slamming brakes for no good reason.

On the plus side, this proves the oil pressure switch and light are working.

[BAMBY]

It only takes a few seconds of metal-on-metal contact to score bearing surfaces.

EXACTLY why this makes me feel uneasy for the sake of my bearings...
 
@happycommuter- by no means is this emergency braking or slamming the brakes... i gradually applied the brakes, and let the forks compress gently- just for the sake of clarity... when you try to replicate this sometime... I will never slam on the brakes like that because going over the bars isnt my idea of a good time...

Also, for those of you that said you have seen the light on under said conditions- what are your forks anti dive settings at, and are you running any pressure in your front shocks?
I have my forks set to 1 on the "trac" dial near the bottom of the left ("driver") fork... and also am running no air pressure in my forks...
maybe putting some more pressure in the forks would limit the dive? but i still could see all the oil sloshing forward under braking anyway.

[Laminar]

I have the TRAC on my Sabre set to 4. Any reason to set it lower than that?

[LOKi]

I will never slam on the brakes like that because going over the bars isn't my idea of a good time...

I don't know what kind of bikes your used to but the NH will not throw you over the bars. Too much front brake will only cause the front to wash out.

Also, for those of you that said you have seen the light on under said conditions- what are your forks anti dive settings at, and are you running any pressure in your front shocks?

I don't think the dive is what is causing this. It's the g-forces acting on the oil. Even if your bike didn't dive at all it would still do the same thing. My bike doesn't have any anti dive settings so there is no adjustment there.

HC is right about the oil. Just because you stop pumping oil for a moment or two doesn't mean suddenly the engine is bone dry. Ever try to clean oil off a metal surface? It doesn't just run off like water. To get it off you have to purposely clean it off and then there is still residue from the oil. In the second or two it takes to come to a complete stop the oil hasn't settled down in the pan leaving the top bone dry. Everything is still spinning in there throwing oil everywhere. It takes a minuet or so of sitting before the oil slowly settles in the low spots.

[gammer]

HC is right about the oil. Just because you stop pumping oil for a moment or two doesn't mean suddenly the engine is bone dry.

+1

I took two Nighthawk S engines apart this summer. Both have sat without oil in the crank case for 2 years, and then sat with old oil for 4+ years.
And even though there was no oil in the engine for the past couple of years, you should have seen the oil still coating the bearings, journals, cams...everything, when I took it aprt.

All that happens when your oil light comes on during hard breaking, is your oil sensor doesn't have enough oil pressure on the sensor itself...you still have oil protecting your important engine bits. And there would be enough to protect it for longer then you think.

Also keep this in mind: if your bike doesn't have enough oil pressure, the second symptom (the first being the indicator light) will be the hydraulic tappets getting noisy. As the tappets are the hardest part to get oil to...they are at the top off the engine and are the furthest away from the oil pump.

In conclusion:
An oil light coming on for a second or flickering during hard braking is nothing to be concerned about.

Amen?

[Laminar]

HC is right about the oil. Just because you stop pumping oil for a moment or two doesn't mean suddenly the engine is bone dry.

+1

I took two Nighthawk S engines apart this summer. Both have sat without oil in the crank case for 2 years, and then sat with old oil for 4+ years.
And even though there was no oil in the engine for the past couple of years, you should have seen the oil still coating the bearings, journals, cams...everything, when I took it aprt.

Oil remaining on a static engine doesn't mean oil will remain on a rotating engine, especially when the rotating parts act like squeegees.

[gammer]

The pickup and screen for the oil pump is closer to the rear of the engine.

True. The screen pick up is near the rear of the oil pan.
However, a couple things to consider:
- The oil sensor sits up higher then the pick up screen sits. If the sensor is detecting no oil, the pick up screen could very well be sitting in oil as it is down lower.
- Designed in the oil pan is an indent to accommodate the pick up screen. At the front of this indent is a tall ridge of metal that would prevent oil from rushing to the front of the oil pan completely. Again, if the sensor is detecting no oil, there is a very good chance the pick up screen still has oil that it is picking up.

The sensor light is a warning...a warning that you are extremely low. Its not a warning that your pick up screen is not grabbing any oil. During hard braking, you need not worry if the low oil light flickers. If it happens under normal driving conditions, pull over asap and shut the bike off, before the oil gets any lower, to the point that your screen pick up actually doesn't grab any oil.

[isleofmanfan]

Back in 1986 I bought a black/orange 700s brand new.  I rode with (a crazy man) a friend of mine that had a 1985 650.  We used to ride down the highway next to any car w/ hotties in it and lock up the front wheel on a semi regular basis.  Neither of us ever had the oil light come on.  That said, I think the oil film on bearing surfaces is sufficient lubrication for that 2 to 3 second period of starvation.  In other words, no worries.  (unless your case isn't full of oil.)

Sometimes on a small block Chevy the press fitted oil pick up tube can fall out, but I highly doubt the Honda has something similar.  Never seen inside the bottom of the case.

[Laminar]

The pickup and screen for the oil pump is closer to the rear of the engine.

True. The screen pick up is near the rear of the oil pan.
However, a couple things to consider:
- The oil sensor sits up higher then the pick up screen sits. If the sensor is detecting no oil, the pick up screen could very well be sitting in oil as it is down lower.
- Designed in the oil pan is an indent to accommodate the pick up screen. At the front of this indent is a tall ridge of metal that would prevent oil from rushing to the front of the oil pan completely. Again, if the sensor is detecting no oil, there is a very good chance the pick up screen still has oil that it is picking up.

The sensor light is a warning...a warning that you are extremely low. Its not a warning that your pick up screen is not grabbing any oil. During hard braking, you need not worry if the low oil light flickers. If it happens under normal driving conditions, pull over asap and shut the bike off, before the oil gets any lower, to the point that your screen pick up actually doesn't grab any oil.

But is the oil light based on a level sensor or a pressure sensor?

[BAMBY]

But is the oil light based on a level sensor or a pressure sensor?

It is a Pressure Sensor, not a level sensor.

And the final consensus will be that for the 1-2 seconds the light is on, one should not worry about internal bearing surfaces...
I think we may have beat this horse dead.

[isleofmanfan]

Also remember that is there is a CORRECT METHOD (detailed in the owners manual) of checking the clutch/engine oil level.  If this procedure is not followed you may be fooled into thinking your level is sufficient.

[BAMBY]

Also remember that is there is a CORRECT METHOD (detailed in the owners manual) of checking the clutch/engine oil level.  If this procedure is not followed you may be fooled into thinking your level is sufficient.

True enough!

[hockeyhawk]

Next time you change oil on a cage with an oil pressure gauge, watch that gauge on start up after the oil and filter change, it sits there for a couple of seconds and then it jumps up to normal gauge readings. Even on engines where you can fill the oil filter before installing it. I've never had a problem with this and I've worked on cars for a living since 1984.  I'd have to think that second the light came on it caused no damage.

One time going way back into my Cadillac days I was replacing an engine in a 1984 eldo. I already had the pan off for diagnosis. We decided to run the engine to see how long it would run before locking up. Well it never did, noisy as a b$%^* but never seized. After about 15 minutes or so we gave up and pulled the engine.

just my $.02

[gammer]

I think we may have beat this horse dead.

Here here! 

[ariwhiteboy]

We used to ride down the highway next to any car w/ hotties in it and lock up the front wheel on a semi regular basis.  Neither of us ever had the oil light come on.

How would you know...you obviously weren't paying attention to the lights on the dash at that point!        

[LOKi]

I'm sure Honda's engineers though of this when they built the bike. "What happens to the oil if you really get on the brakes". or more likely "What if brakes applied will oil go off engine". Either way they aren't going to design an oil pickup in a way that will hurt the engine if you hit the brakes to hard.

Everyone keeps saying Honda engines are bullet proof. That indicates that it was well conceived design and built very well. Of all the things you have to consider in motorcycle engine design g-forces are up there. They aren't going to overlook something as critical as supplying the engine with oil when stopping.

Where is the smiley whipping the dead horse?

[chas550sc]

Also remember that is there is a CORRECT METHOD (detailed in the owners manual) of checking the clutch/engine oil level.  If this procedure is not followed you may be fooled into thinking your level is sufficient.

True enough!

IN the case of the 83 550, tha is on centerstand, without screwing in the dipstick.