Topic: CB750 Oil Pressure - Got oil pressure gauge now title amended

[Ace]

G'day all,

After pulling my clutch apart, I noticed that the first two inner frictions plates were somewhat dry. Other issues were not being able to select neutral when hot. Did a search and Terry also mentioned that maybe I have an oil pressure issue. Seems reasonable.  So I've got an 836 kit, about 2500 kms since rebuild and it takes 22 kicks to get the oil pressure light to go off. Oil is Motul 10-50W about 100 kms old so new. I did the same to a stock CB750 engine, 3 miles since rebuild and it took 8 kicks for the light to go out.

I'm thinking 22 kicks is rather long to build the pressure, on start up light goes out within seconds.  Maybe I should start a poll, but I'm interested in CB750 owners and how many kicks it takes to get your oil pressure light to go off when the engine is cold, how many miles and viscosity of oil.

I've ordered an oil pressure gauge and I have a slow weep out of a bolt hole in the top end so I'll tear it down soon.

Cheers.

[bjbuchanan]

Temperature could be a major factor here. I would rather workout in the gym tho than test this, I twist the key and if off idle that light doesn't trip off I get a little worried

[Ace]

Temperature could be a major factor here. I would rather workout in the gym tho than test this, I twist the key and if off idle that light doesn't trip off I get a little worried

Temperature is about 24 degrees in my garage maybe 28, not cold and not hot either.  A couple or a dozen or so kicks and you would rather go the gym.....only if there was something good to look at 

[Jerry Rxman Griffin aka MuthaF'er]

Can't say I've seen anyone count how many kicks it takes for the light to go out?? It's based on pressure so when you're not kicking/between kicks why would there be as much pressure? And better yet, how is this relevent? Guess I just don't understand.

[AJK]

Hi Ace,

Here is a pretty good link on the clutch basket mod as well as ways to improve the shifting when hot.
http://forums.sohc4.net/index.php?topic=78643.0;all

You might have old o-rings in the oil pump that is causing you grief. The info in the link above might get you sorted.

cheers
Alex

[Ace]

Hi Ace,

Here is a pretty good link on the clutch basket mod as well as ways to improve the shifting when hot.
http://forums.sohc4.net/index.php?topic=78643.0;all

You might have old o-rings in the oil pump that is causing you grief. The info in the link above might get you sorted.

cheers
Alex

Thanks for the info Alex.  I've done the clutch basket mod on rebuild, used new orings and did a thread search. That's where I came across other with similar problems. Adjusted clutch as per Hondaman's method.

Between kicks, well kick it over, kick starter returns back to the top and then kick again. Oil moving through the system to build up pressure. If people get the oil pressure light to come of say between 7 to 14 kicks and mine takes a lot longer then I possibly have a problem, given also my clutch issues.

I was told by an engine builder, prime the pump on installation, make sure number 4 intake valve is closed, pour 1 litre of engine oil over the valve to get some in the bottom of the engine, rest goes in the oil tank, kick over about 7-10 time to build the pressure up in the system and start it up.  This method was for initial start up after reassembly.

I'm keeping options open. I only have one CB750, a forum has many so hoping to get some help.  Cheers.

[AJK]

Hi Ace,

Here are a few links on priming, however it may be linked to your problem, or at least there might be some useful info in there for you.

http://forums.sohc4.net/index.php?topic=101556.0;all

http://forums.sohc4.net/index.php?topic=59561.0;all

http://forums.sohc4.net/index.php?topic=19948.0


The 3rd link says similar to what your engine builder said.

I.e. the 3rd link at the bottom of the page quoted from 'Clyde'
-----------------------------
Your oil pump is probably full of air and will not prime.
Pour half a liter of oil down through any of the valve adjustment holes.
With the bike on the side stand undo the small oil gallery plug which is situated on the right hand side near the points cover (probably where your gauge is connected). Pour as much oil as you can until it can take no more.
Put the bike on the centre stand and you should have oil pressure when you start
Regds Clyde
-----------------------------

I can vouch that this method definitly works. You should get oil pressure after about 15 to 20 kicks if you do this. Filling the side galley is the key.

cheers

[nccb]

If I am remembering correctly (haven;t kicked it in a while), mine typically goes off within 2-5 kicks i think. 

[MCRider]

IIRC, you can't kick it hard enough or long enough to get the light to go out.

Do all the priming steps mentioned. Hit the starter with kill switch on for a few bursts, not more than 5sec each. Then start it. Oil pressure gauge should read, light should go out. Leaving the #1 and 4 exhaust caps off, oil should fling off the rockers in about 15-30 seconds.

[Ace]

I've never had a problem with priming an oil pump or the light going out after a few seconds or running any time.  What I'm concerned about is lack of oil pressure causing my friction disks in the clutch drying out.  Clutch mod done so I should have plenty of oil on the plates, not dry spots on the inner two.  Can't find neutral when running, all indicating to possible oil pressure problems.

[Hastenbrucke]

   ACE, you gotta get one of those hybrid K2/K3's , never have oil pressure issues, wiring issues, carby issues or anything......LOL

[Ace]

  ACE, you gotta get one of those hybrid K2/K3's , never have oil pressure issues, wiring issues, carby issues or anything......LOL

Hopefully for you I've learnt from my mistakes then 

An absolute joy to get yours back on the road.  Can't wait to meet up for a ride and turn some heads even though you have a.......an interesting CB750 K model   

[Ace]

Righto, I installed the oil pressure gauge from Cyclex. Oil is Motul 5100 4T 10W-50 about 200 kms old, new filter when oil was changed. Engine around 2000 kms old. Hard finding neutral at lights and inner clutch friction plates 1 and 2 have dry patches on them after a 30 mile trip.

Pressure on start up 85 psi about 1400rpm. Over the course of the next 15 minutes the pressure dropped down to about 4psi, rpm about 1200. Pics are below, the needle on the tacho fluctuates about 2000 rpm during idle so I take the average of the fluctuation hence it looks like 1400 rpm and 2 psi.

Increased the revs up to the follow, time about 15 mins after initial start.
5000 rpm 65 psi
4000 rpm 55 psi
3000 rpm 43 psi
1200 rpm 2 psi

Oil pressure problem I'm guessing. Anyone else have any readings to compare? Thanks.

[cheftuskey121]

That looks like how my oil pressure gauge is when the bike is warmed up and running. Seems like the oil pressure is fine unless the light is coming back on during idle. Make sure your clutch is adjusted, I had mine releasing way too early and I could never find neutral. Adjusted it to release a little later and I can get into neutral easier. Maybe you should pull your oil pump and get a new spring, stopper, and o rings from Elan to freshen up your pump.

[AJK]

Hi Ace,

My story is somewhat similar, but the low readings are no where near as low as the 2 psi that your seeing. With 2 psi i'm assuming your oil light is coming on ??

I start mine up, goes to about 70 psi at cold. Ride for say 10 mins, drops to about 60 psi. Rides around at 60 psi consistently for about half an hour after that.

After a good 30 to 40 mins riding, the oil pressure starts to drop to 40 - 45 psi nominal under a constant hot oil temperature. At this temperature mine idles with about 18 to 20 psi, sometimes coming down to 15 psi. I have my idle set at 950 rpm.

So I can only attribute the description above to the oil thinning out at normal running temperatures since the readings drop consistently with the engine & oil heating up.

I havn't done any clutch basket mods, nor have i touched my oil pump seals. This will be something i'll do in the next year or so as per described in the other thread.

I have a VDO gauge (non oiled type) that looks similar to yours. I was told by the guy off ebay not to get the one your've got because they don't read accurately. I can't testify to this, but just what this guy told me. Could be BS, dont know.
  My guess is that if your oil light is going off, then you are seeing below 5 psi or whatever the pressure switch is calibrated at, otherwise your gauge might not be that accurate at the low end of the scale. Just some thoughts.

I'd say try 20W50 and see if that fixes it, at least in the summer anyway. Hondaman suggests 15W50 should be the minimum as the top end chews up the oil.

After 1000 miles (1600 kms), I've noticed that my gear changes become very combersome & difficult at operating temp and this I found to be true at around the 1600 km mark. I ran Motul 3000 15W50 which is just mineral.

I'm going to run 20W50 in the summer and 10W40 in the winter & stick with 1000mile oil changes. Something like that anyway.


PS: If your seeing 85 psi at cold, your oil pump spring relief valve is likely ok. You mentioned that you replaced the o-rings as well. Sounds like you have a fairly normal running bike, but it would be interesting to know what the condition of the bearings are out of interest if you know.

[Ace]

G'day AJK, if cyclex started selling dodgy gauges I'll let everyone know about it.  I would have purchased the white faced and chrome one they sell but it wasn't available at the time and I was trying to make the most out the holidays.

I didn't change the big 46mm orings in the oil pump, but changed the rest. My pump also has the spacer washer to increase the oil pressure. Complete bottom end rebuild, crank, all bearings etc. I have all new orings including the 46mm ones so I'll change them out and then post back.

I've adjusted the clutch as per Hondaman's description but have yet to test it as I was waiting for my gauge.

Mobil produced a good oil but they don't make it anymore. Motul is supposed to be good and I got it at a price I couldn't refuse. I read one of Hondaman's comments the other day about 15W-50 oil. 

My oil light didn't come on at all even when reading 2 psi on the gauge.

Clutch adjusting.....fug me, I've had it apart, changed from early to late model setup, changed plates and still it's not working like it should.  Common element is me in the process. I remember before the rebuild you could have the clutch lever pulled all the way in, release it 5 to 10 mm and it would start to take up and go. Now it's right at the other end of spectrum, just about all the way out. Bolt and nut are about 1/4 turn out at the hub. Maybe the neutral switch is in a little too far.....but dry plates indicate oil supply issue.

Anyway, back to the garage or I might just watch the cricket.

[AJK]

Sounds like your machine is in pretty good order after your rebuild. I doubt your 2 psi reading is anything to worry about since your light is not coming on.

Even Honda said that intermittent flicking of the light at idle "was normal" and nothing to worry about, so I guess this was indicative of pressure falling below the 5 psi or whatever the pressure switch was set at. If your not seeing the light come on, then i'm sure theres nothing to worry about.

The big o-rings might be something to replace down the track, at least after the crickets over anyway. I'll do the same one day.

Re the gauges, this was just what i was told. I remember the bloke saying that those gauges read fine when the oil is cold, but become inaccurate when the oil gets hot. Again, don't know if this was his sphincter talking or something half worth considering. I just bought his VDO gauge and too be honest, its looks the same as yours, so probably the same $#^t.

[Ace]

Sounds like your machine is in pretty good order after your rebuild. I doubt your 2 psi reading is anything to worry about since your light is not coming on.

Even Honda said that intermittent flicking of the light at idle "was normal" and nothing to worry about, so I guess this was indicative of pressure falling below the 5 psi or whatever the pressure switch was set at. If your not seeing the light come on, then i'm sure theres nothing to worry about.

The big o-rings might be something to replace down the track, at least after the crickets over anyway. I'll do the same one day.

Re the gauges, this was just what i was told. I remember the bloke saying that those gauges read fine when the oil is cold, but become inaccurate when the oil gets hot. Again, don't know if this was his sphincter talking or something half worth considering. I just bought his VDO gauge and too be honest, its looks the same as yours, so probably the same $#^t.

Probably both made in China or Taiwan.

[AJK]

Yep, can't think that they would be made anywhere else these days.

Interestingly, your 0 psi reading starts a bit higher than mine, so they might be a little different. My 0 psi starts at the stop, but yours starts a bit higher up.

Mine has no oil in it to dampen the needle, so my need vibrates a bit when running.

[dave500]

man come and ride with us,you wont be looking down at any gauge.

[AJK]

man come and ride with us,you wont be looking down at any gauge.

Are you coming down or am i coming up? We about 1000kms apart. Ace is in Perth!
Is the beer cold? XXXX

[dave500]

if your spending time watching an oil pressure guage your not really having fun?especially in such an unergonomic location?"im just peaking in third,rounding up a slower rider,ill just check my oil pressure?"i never have to check the beer temp its always cold!

[AJK]

if your spending time watching an oil pressure guage your not really having fun?especially in such an unergonomic location?"im just peaking in third,rounding up a slower rider,ill just check my oil pressure?"i never have to check the beer temp its always cold!

I went with the gauge because i had a dodgy switch that was stuck & was getting me worried during priming. I had pressure, but the oil light was permanently on and the wiring was perfect. I since replaced the switch and it worked as expected, so my original switch was stuffed. Not wanting to take further chances, I went with the gauge. The gauge can tell you a few things that a switch alone won't show up, like how different oils perform. Funnily, the seat of the pants feedback that the bike returns (like hard shifting, etc) coincides with the gauge, so one could probably do without it.

I peak it in 3rd as well, one eye on the road and the other on the gauge! 

The fun is definitely there, albiet in an unergonic environment, that part i'll concede. They say the best thing about Sydney is the road out of it, no disagreement from me there.

Save a coldie for me.

[dave500]

ha ha cool man!ive always got a coldie for anyone,yeah dont be too concerned with the actual pressure,its not a real issue,some fit gauges to impress chicks and small dumb animals?like themselves?

[AJK]

ha ha cool man!ive always got a coldie for anyone,yeah dont be too concerned with the actual pressure,its not a real issue,some fit gauges to impress chicks and small dumb animals?like themselves?

Hah, Dave, you made me laugh mate. Yeah, i tell ya, these gauges really pull in the chicks! I highly recommend them. Not sure about Aces one but mine pulls 'em in like a magnet. But wait, theres more, it also tells me the oil pressure!

Looking forward to our beer!