Topic: Why is my bike popping the Oil Pressure sensor?

[Itineo]

Hi All, and thanks first of all for the helpful answers a few weeks back to my questions on brake bleeding. Naturally as soon as one issue is sorted another crops up.
Briefly to recount the story of my bike, It is a 1979 CB550f that I imported to Ireland from the UK in 2004, rode it for a few years, parked it up while I had a bit of a romance with modern bikes. I resurrected it this spring and during Covid sent it to a very well respected old school bike shop nearby (owner/mechanic rode a CB550f from Ireland to Australia in the early eighties) to get it right. On the way home it burst the top of the oil pressure sensor causing an oil leak. I got a good quality ( Bosch ) equivalent replacement part and within ten minutes on the road it went the same way again. I kept the revs low until the engine was warm but it didn't make a difference. I remember replacing the same item back in 2010 for the same reason.  So it it seems there is an underlying problem. 
I see the oil level is a little high but I'd assume the oil pump/relief valve setup would make this irrelevant?
I'm not sure what oil grade went in to it but again I'd be surprised if it wasn't the correct one as the shop has been working with this model for forty years.

My plan is to drain and replace the oil with the Honda specified grade to the correct level, replace the switch and hope for the best.  Is there anything else in your experience I should be looking at.
Thanks in advance for your advice.
Itineo.

[bryanj]

Manufacturers name means nothing as they all buy them in BUT  a car one is not a good idea as they operate at a different pressure.
If the oil pump pressure was that high i would expect to see other oil leaks everywhere there is an O ring seal so most likely poor quality replacements.
You could check the oil pressure with a gauge, the thread is a fairly standard one

[Bankerdanny]

That is very odd. My 550F had a pressure gauge on it and never exceeded 70psi with cold oil. Your bike shouldn't be producing sufficient pressure to make the sensor pop like that.

You have a '79 or a '78? In the US Honda didn't offer a 550 in '79, only the 650. Europe might have been different.

You might want to put a gauge on it to actually measure the pressure. You can use a standard automotive gauge available at most auto parts stores. Remove the pressure switch and put an adapter (usually included with the gauge) where the switch went and then run the tube to the gauge from that.

[bryanj]

550 sohc did not exist in 79 unless it was an old stock item

[Deltarider]

Bryan, a friend of mine owns a CB400F that was first registered 1984. When he bought it, it had been in the showroom for years. He wants to sell it. What do you or anyone here suggest he puts in the advertisement? See? Denominating the bike by year doesn't make much sense. If he mentions the model by Honda speak and also mentions the first year it was allowed to the roads, everybody will have all the information, so there cannot be any misunderstanding. So it would be: CB400F2, first registered 1984.

[Kevnz]

It's pretty hard to make hard and fast judgments on these issues. I have a 550K0, that according to official  (NZ equivalent of MOT) data was registered in 1980 new as a 1977 model. Problem is it has a 1974 K0 frame number and 1976 engine number, and was registered as green. It's clearly not a 1977 (550K) and according to this site, green was not a 1976 colour. Paint found on the underside of the tank and sidecovers was Freedom Green Metallic, which was a 1974 only colour. How hard would a dealer in 1980 have to work to sell a bike that looked near enough identical to a (500) of 1971? Remember, the opposition, and Honda itself was all DOHC, by then ( CB650 apart)

[bryanj]

If it was me i would describe it as " A Honda CB 400 F2 built in **** but not registered for use till ****" then there can be no comebacks

[bryanj]

I know from when i worked in a Honda dealership that honda offered incredible discounts on "old" models still in stock in crates when new models came out, hence in UK i have seen 1979 and even 1980 CB550K3 and CB750F2

[robvangulik]

If it was me i would describe it as " A Honda CB 400 F2 built in **** but not registered for use till ****" then there can be no comebacks

That is the only correct way!

[Itineo]

Hi all,
Interesting point about the year of the bike. Despite having it for years and owning the Haynes Manual with '1973 to 1977' written in large letters on the cover I'd never actually thought about that. Quite obvious now it's been pointed out.
It's a CB550F2 with the frame number beginning CB550F2 21*****. It was first registered in the UK on 25 May 1979.  I have the receipt showing the first owner purchased from Slocombes of Neasden in August 1980 for the princely sum of £845. So I guess it must have been sitting around somewhere for a while as Brianj said.
You learn something new every day
There aren't any oil leaks and the bike is running fine otherwise. Going by the replies I think I should bite the bullet and get the OEM part?

Itineo

[Itineo]

Manufacturers name means nothing as they all buy them in BUT  a car one is not a good idea as they operate at a different pressure.
If the oil pump pressure was that high i would expect to see other oil leaks everywhere there is an O ring seal so most likely poor quality replacements.
You could check the oil pressure with a gauge, the thread is a fairly standard one

I should add that I sourced the replacement switch using the Honda OEM part number and it pointed me to a seller that seemed to specialise in German cars. So I guessed they were a generic part. They had the part number (among a hundred others) matched to the item.  I used to have a Diesel engined car that had an oil pressure gauge a long time ago - I seem to remember it running around 80psi cold, dropping to 40 when warmed up on idle - which isn't that far from what the other posters noted using a gauge.
I don't have one but a nearby car garage may have - I'll try giving him a call.
Thanks for the interest and useful advice.
Itineo

[Nurse Julie]

This is the correct oil pressure switch, I sell these on my ebay page in UK. If you have problems sourcing one, send me a PM.
Just out of interest, you say the switch keeps 'popping', is the tapered thread in the top casing not knackered by now 🤔🤔🤔😁😁😁

[Itineo]

PM sent.

[Itineo]

This is the correct oil pressure switch, I sell these on my ebay page in UK. If you have problems sourcing one, send me a PM.
Just out of interest, you say the switch keeps 'popping', is the tapered thread in the top casing not knackered by now 🤔🤔🤔😁😁😁

I get the joke It's been changed three times. No the taper thread is fine. As an aside I was surprised at the amount of torque it needed to remove the old one and fit the new. I know a wee bit about screw threads (I've made a few in my time) and was surprised to see such a fine pitch in an aluminium casing - asking for trouble -  but no it's ok.

[bryanj]

Its that fine because its one of the few non metric threads used by Honda 1/8 npt if memory serves

[scottly]

Manufacturers name means nothing as they all buy them in

Bosch was an OEM supplier of electrical parts to many manufacturers, just like Lucas was to British makers, except the Bosch stuff worked well, unlike the Lucas "Prince of Darkness" crap.
Itineo, if you really are blowing the top off the oil pressure senders, you have some sort of blockage in the output of the oil pump, and/or a malfunctioning pressure relief valve, although I can't imagine how much pressure it would take to do that? I wouldn't risk damaging a borrowed gauge to try to measure it; if it's popped three senders, something is wrong! A "spun" main bearing can cause an increase in oil pressure, as the shell blocks off the oil passage in the block. Are you getting oil up to the top end of the motor? 

[Nurse Julie]

PM sent.

PM returned. Thank you

[Itineo]

PM sent.

PM returned. Thank you

Thanks for your advice - I'll get the Oil pump kit and sensor from you via your facebook page.
Much obliged.
Itineo.

[Itineo]

Manufacturers name means nothing as they all buy them in

Bosch was an OEM supplier of electrical parts to many manufacturers, just like Lucas was to British makers, except the Bosch stuff worked well, unlike the Lucas "Prince of Darkness" crap.
Itineo, if you really are blowing the top off the oil pressure senders, you have some sort of blockage in the output of the oil pump, and/or a malfunctioning pressure relief valve, although I can't imagine how much pressure it would take to do that? I wouldn't risk damaging a borrowed gauge to try to measure it; if it's popped three senders, something is wrong! A "spun" main bearing can cause an increase in oil pressure, as the shell blocks off the oil passage in the block. Are you getting oil up to the top end of the motor?

I'm hoping that this isn't the case - [size=78%] [/size] [/size][size=78%] [/size]
[/size]The engine hasn't ever been opened up and has 31000 miles only so I'd be hopeful that the bearings are still where they should be. Yes there's oil getting to the top end. I've ridden it a fair bit in the meantime and I'd imagine I would have chewed up the camshaft if there wasn't oil getting there. [size=78%]
[/size]I'll do the oil pump first and see how it goes as the least complicated option.
[/size]

[bryanj]

Over pressure but the amount needed to break sender units would mean black stuff pouring out of just about every sealed orifice. I think you have been unlucky with sender units or are cracking the tops when fitting

[Itineo]

Over pressure but the amount needed to break sender units would mean black stuff pouring out of just about every sealed orifice. I think you have been unlucky with sender units or are cracking the tops when fitting

I was careful fitting the unit - so maybe you are right. As the oil pump is fairly accessible I'll go belt an braces and do that as well.  I've seen oil pumps shred themselves in the past in cars I've owned and I think it is more likely the the switch is the problem. TBH i'm not worried about the engine per se but more about the oil leaking when I visit anywhere. I dissolved the brother in law's tarmac with a leaky carb a while back so I'm trying to be less antisocial. 

[Itineo]

This is the correct oil pressure switch, I sell these on my ebay page in UK. If you have problems sourcing one, send me a PM.
Just out of interest, you say the switch keeps 'popping', is the tapered thread in the top casing not knackered by now 🤔🤔🤔😁😁😁

Thanks Julie for your interest and advice.

I got hold of an oil pressure gauge and the oil pump seems ok - around 75psi on idle cold rising to 80-85 when revved. So it seems I'm just unlucky with the choice of replacement parts.
Joking aside I'd be worried about the thread - it takes more effort to get an oil tight seal each time the switch goes back.
I've ordered the item just now from your eBay page.

Itineo.

[Bodi]

Several I have put gauges on showdd the bypass activating at 60psi, getting to 65-70 revved a bit on cold oil. Your pressure seems high. Most get ~20psi at idle on a hot engine... one engine after a full rebuild (new bearings) and new pump rotors about 40 at hot idle. Hot maxes out at 60 where the bypass opens.
I think an inspection of the oil pump is in order. I have seen one with shims in the bypass to increase bypass pressure - this is pointless in my opinion. Yours may be stuck shut?

[Itineo]

Thanks. I think the engine has 20/50 oil and cold here in Ireland is about 16C ( in mid summer !) So I’d think the oil pressure is about ballpark.  I didn’t warm the engine up as the pressure was more or less constant - within reason -  at higher revs. And Mrs Itineo Wasn’t happy with the noise 😀 So I’d assumed the bypass valve was doing it’s job. Thanks for your detailed and knowledgeable reply. Is 20
psi cold difference big issue in your experience?