Topic: Oil Pressure Gauge & Whats Considered Normal Readings

[736cc]

My oem oil light is glowing alarmingly when bike is warmed-up, and staying on . Usually it just flickers during its lumpy-cam idle, so this is something new. Ran great when it did this on a turnaround-and-get-home 2 mile ride today. When I re-started it an hour later, red light not on, then it flickers, then it stays on after a minute. Oil is fresh, level ok, and is doing slow laps in the oil tank when I peek during a running inspection. I'm not riding again until I install an oil pressure gauge. What numbers should I get? Hot, cold, idling, hwy speeds etc.
Do heavily-modified motors get different readings than stock?

[edbikerii]

When I switched from Castrol GTX 20W/50 to Rotella T 15W/40 in my 1977 CB550K the oil light would come on below 2K RPM whenever the bike was fully warmed up.

It started acting up on the first ride after about 10 miles from a cold start.

I tried:

1.  Replacing the oil pressure switch with new.  This made no difference.
2.  Adding STP oil treatment to the Rotella T 15W/40 oil.  This extended the no-light period to 14 miles after cold-start.

The resolution was switching back to Castrol GTX 20W/50 oil.  I have since ridden a couple hundred miles with no oil light issues.

My bike has fairly low mileage at less than 27K miles, so I don't think there are any excessive bearing or oil pump wear issues.

I think the bike just likes 20W/50 better.

[Bob Wessner]

On my 750, I get about 10 lbs per 1,000 rpm in the summer after warm-up, that is the engine is as warm as it's going to get and the outside temps around 80F. That was with 10w40. This year I started using 5w40 and readings remain the same. Cooler spring or fall temps raise the pressure a few lbs per 1,000 rpm. Cold start-up pressure runs between 70-80 lbs. Now all this assumes a certain degree of accuracy on the gauges part.

[Steve F]

I generally have the following pressures:
cold at idle: 50psi
hot (as in summer day in traffic at idle) 10psi
cruisin at 55 bike warm 60+psi (hot or cold weather)

Have a glycerine filled gage on the oil gallery plug, so I don't rely on the light.  The light is there to tell you when it's too late to shut down   

[dusterdude]

what bob said is par for the course on a plain bearing engine.

[Jerry Rxman Griffin aka MuthaF'er]

My numbers are right in line with Steve's. 30K hard miles on the original oil pump. My engine is medium modified. These readings are with an old S-W gauge that is not liquid filled. Castrol GTX 20W-50.

[bender01]

My 75 550k with 11k miles has an oil light that comes on after a 30 minute 70 mph ride. It only comes on at idle to 1400. If i give it some gas its groggy til 1400 then all is good and light out. Ive been reading lots of other threads so I switched from honda gn 10w-40 to valvoline 20w-50 specifically for motorcycles. I also pulled the oil pan to look for gunk and there wasnt hardly any. screen was fine. I just took it for a good hard run 60- 80 mph for 30 minutes and the light is coming on still now from idle to 1800. Is it possible my oil pump expands or something when hot to not operate properly?. the bike runs great at speed and will idle fine as soon as it cools a little. Im in SC so the climate here is always nice. Today its 70.Thanks for any direction.

[LoopsAndLogic]

I heard this problem before, but I've asked a some guys with 400f's and none of them have had this problem.

My question is, is the first number on the oil container the starting weight or the weight when it's warmed up??

The higher the number the heavier??

It's been awhile since I've read into the numbers.

Thank you!

LL

[Bodi]

The low/first number is the cold viscosity.
Same pressures with my 400F, new oil pump but original bearings and probably 40,000+ miles (new speedo after a fall and I can't remember what it was reading). 10psi or so hot idle, 50psi or so hot maximum, cold it's about 40 at idle and bumps the pressure relief at 60 when turning faster.
I thought those pressures were low and got a NOS pump, a bit higher overall but no big change. If I could find the $$$ I would get a modified pump from Kevin.

[alltherightpills]

This is sort of off topic, but where does one get one of those gauges that goes on the oil gallery plug?  I removed all of the idiot lights, except for the oil pressure indicator and it is currently just hanging by the wire.  I've got a 78 550k, and would like to rely on the gauge and get rid of the light.  I've looked for 'em, but not terribly hard. 

Zach

[paulages]

the race bike (590cc cb550) shows 70-80PSI almost constantly.

[mikedialect]

This is sort of off topic, but where does one get one of those gauges that goes on the oil gallery plug?  I removed all of the idiot lights, except for the oil pressure indicator and it is currently just hanging by the wire.  I've got a 78 550k, and would like to rely on the gauge and get rid of the light.  I've looked for 'em, but not terribly hard. 

Zach

ebay, ebay, ebay.

http://cgi.ebay.com/ebaymotors/Honda-CB750-CB-750-Motorcycle-Oil-Pressure-Gauge_W0QQitemZ160189192356QQihZ006QQcategoryZ35595QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[bender01]

A new pump is 240$ from honda.  I dont think my pump works at low rpm when its hot. I guess ill take it out, look at it to see if its plugged which I doubt. maybe its worn but at 11k miles it seems unlikely to me . Im the 2nd owner and the PO didnt abuse it. Can they be rebuilt. Is the oil gallery plug under the points cover on a 550? if so will that pressure guage fit? I do wish I could check my pressure when it happens again. Theres a toy run this weekend and out of @ 300 Ill surely be the only sohc there but now i dont think ill go. Its only 40 miles round trip and I did want to  show it off. But i dont want too have 300 guys come by going what HAPPENED.
thanks for reading. Merry Christmas

[Steve F]

This is sort of off topic, but where does one get one of those gauges that goes on the oil gallery plug?  I removed all of the idiot lights, except for the oil pressure indicator and it is currently just hanging by the wire.  I've got a 78 550k, and would like to rely on the gauge and get rid of the light.  I've looked for 'em, but not terribly hard. 

Zach

ebay, ebay, ebay.

http://cgi.ebay.com/ebaymotors/Honda-CB750-CB-750-Motorcycle-Oil-Pressure-Gauge_W0QQitemZ160189192356QQihZ006QQcategoryZ35595QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Wow.  50 bucks plus shipping?  I bought the same gauge from Grainer.com for about $12, and tapped my galley plug for 1/8 NPT.  Call me cheap......I don't care.  BTW, you CAN tap the stock galley plug with no issues.

[mikedialect]

This is sort of off topic, but where does one get one of those gauges that goes on the oil gallery plug?  I removed all of the idiot lights, except for the oil pressure indicator and it is currently just hanging by the wire.  I've got a 78 550k, and would like to rely on the gauge and get rid of the light.  I've looked for 'em, but not terribly hard. 

Zach

ebay, ebay, ebay.

http://cgi.ebay.com/ebaymotors/Honda-CB750-CB-750-Motorcycle-Oil-Pressure-Gauge_W0QQitemZ160189192356QQihZ006QQcategoryZ35595QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Wow.  50 bucks plus shipping?  I bought the same gauge from Grainer.com for about $12, and tapped my galley plug for 1/8 NPT.  Call me cheap......I don't care.  BTW, you CAN tap the stock galley plug with no issues.

This is also true- some folks don't do such a clean tap job, so it's more aesthetically pleasing to use a made to fit plug. The quick and cheap approach is always best, though

[bgfootball67]

Need some insight from those of you that are currently running an oil pressure gauge.  On my 1973 CB 750, I will need a 100 psi gauge for the oil pressure?  The only reason I ask is because my GS 1000 only needs a 15 psi gauge, that bid of a difference from a SOHC to Suzuki DOHC?  Also, anyone know if the oil galley plug is 14 mm or 18 mm, or what size?  Thanks in advance for your help!

[736cc]

  GS1000 Suzi's use ball-bearing cranks (Honda uses plain) which don't need much oil pressure

[bgfootball67]

I figured it was something like that, thanks for the help.  Anyone know the size of the oil galley plug where the pressure gauge is mounted?

[HondaMan]

My oem oil light is glowing alarmingly when bike is warmed-up, and staying on . Usually it just flickers during its lumpy-cam idle, so this is something new. Ran great when it did this on a turnaround-and-get-home 2 mile ride today. When I re-started it an hour later, red light not on, then it flickers, then it stays on after a minute. Oil is fresh, level ok, and is doing slow laps in the oil tank when I peek during a running inspection. I'm not riding again until I install an oil pressure gauge. What numbers should I get? Hot, cold, idling, hwy speeds etc.
Do heavily-modified motors get different readings than stock?

The "standards" I went by (young engines, of course) were:
20w50 gives 35 PSI hot at 1000 RPM, over 50 PSI at 4000+ RPM hot.
10w40 gives 5-15 PSI hot at 1000 RPM, over 40 PSI at 4000+ RPM hot.
Honda's oil switch, though, has these specs (actual tests on a new and used unit):
On rising pressure, OFF at 55 PSI cold, 45 PSI hot.
On falling pressure (i.e., it is already OFF), ON at 15 PSI cold, 5 PSI hot.
I also found that the 20w50 oil delays the turn-ON point, due to the small hole size and oil viscosity.

There are 2 (non-bearing) places where oil leakage inside the engine will lower pressures:
1. The oil pressure relief valve can get stuck open a little by debris.
2. The oil filter's bypass valve can get stuck open by debris. Another item here: is your oil filter has no washer in between the spring and the filter, get a washer. This can let the filter leak when hot, too, very common. If the filter's spring is old, get a new one. They lose tension over the years.

The former (pump) can be checked in the 750 by dropping the pump from the engine: make sure it's got good O-rings on the dowels where it connects into the oil hose passages in the cases. If yours is missing the dowels (surprisingly common), get some, and new 15x2.5mm O-rings.

Add several of these together, 736, and you'll get the symptoms you describe.

[cyco72]

I'm in the middle of this project now. You can buy a guage from j&p cycles anywhere from $26.99 to $50.00 and thats for a nice vdo or an accel. I've installed mine where the oil sending unit was, that seems to work.

[Vin750]

The "standards" I went by (young engines, of course) were:
20w50 gives 35 PSI hot at 1000 RPM, over 50 PSI at 4000+ RPM hot.
10w40 gives 5-15 PSI hot at 1000 RPM, over 40 PSI at 4000+ RPM hot.
Honda's oil switch, though, has these specs (actual tests on a new and used unit):
On rising pressure, OFF at 55 PSI cold, 45 PSI hot.
On falling pressure (i.e., it is already OFF), ON at 15 PSI cold, 5 PSI hot.
I also found that the 20w50 oil delays the turn-ON point, due to the small hole size and oil viscosity.

There are 2 (non-bearing) places where oil leakage inside the engine will lower pressures:
1. The oil pressure relief valve can get stuck open a little by debris.
2. The oil filter's bypass valve can get stuck open by debris. Another item here: is your oil filter has no washer in between the spring and the filter, get a washer. This can let the filter leak when hot, too, very common. If the filter's spring is old, get a new one. They lose tension over the years.

The former (pump) can be checked in the 750 by dropping the pump from the engine: make sure it's got good O-rings on the dowels where it connects into the oil hose passages in the cases. If yours is missing the dowels (surprisingly common), get some, and new 15x2.5mm O-rings.

Add several of these together, 736, and you'll get the symptoms you describe.

Hi Hondaman,

I realise this is a 10 year old thread but here it goes.

From your experience, does that 10 psi for 1000 rpm make sense? So if my bike isles at around 10 psi oil pressure hot. Is that good enough? It hits close to 70 when about 4000 rpm.

Do you think using synthetic oil will reduce the oil pressure? That is using the same viscosity oil as the non synthetic. And good quality oil.

Thanks



Sent from my iPhone using Tapatalk

[Bodi]

The oil pressure gauge is a decent hydraulic tachometer but the readings shift with temperature and oil type. There is a pressure limiter built into the pump at roughly 60psi but with cold viscous oil it can't flow enough and max pressure will be higher whilst warming up.
Idle pressure can be quite low with no damage, bearing stress is minimal at idle.
I have no clue what the real minimum acceptable pressure is at riding rpm. Honda was OK with the warning light tripping below 10psi though...
On the 400F I get around 40psi on the highway on a hot day, around 10 at idle. Rotella 6T. New pump and original bearings, mileage...... speedo replaced some time back and the records long lost.
I think it best to keep the idiot light. Unless a gauge is at the triple clamp it won't be easily visible. The typical gallery cap location requires some contortion - and definitely looking away from the road ahead - to read. If something bad causes pressure loss the light might get your attention in time ... a gauge down by your foot would just confirm why the motor self destructed.

[PeWe]

An electrical sensor in gallery cap location, cable beside the tacho-speedo and a small gauge visible.
Oil temp would be fine too.

[Bodi]

I have looked for such a thing, all I find are car gauges - too big and not waterproof. There are some motorcycle instruments that can display sensor info like oil pressure & temperature, and voltage etc... but they cost $$$ and I like the original gauges just fine.

[HondaMan]

I have looked for such a thing, all I find are car gauges - too big and not waterproof. There are some motorcycle instruments that can display sensor info like oil pressure & temperature, and voltage etc... but they cost $$$ and I like the original gauges just fine.

Maybe check some of the vintage car sites for their oil PSI gages: I had them in all my 1960s cars, little ones mounted under the dash. They are 2-1/8" diameter, and can be had in both mechanical (which I wouldn't on a bike...) and electrical. It was popular (back in the 1970s) to put one on the handlebar clamps' upper 2 bolts: maybe eBay or some bikeyard could turn up an old used bike handlebar mount for one?