Low oil pressure on Ducati 750SS

I recently purchased a 1999 750SS that was “race ready” (well we all know how that goes) and after fixing a lot of miscellaneous things I’ve come up with a larger issue. Like the title says, it has very low oil pressure. The oil light will come on when you turn the key and go off shortly after you start it, but will come back on once it warms up. It will stay on unless you give it some revs then it will go off, but come right back on as it drops back down to idle.

I put an oil pressure gauge on it last night and at cold idle it has around 16PSI, but once it warms up that drops down to 5-6PSI. If you rev it up to around 4K the pressure goes up to around 56PSI which is better, but from what I’ve read still seems low.

I’ve googled myself crazy and the two things that keep popping up are bad (or failing) oil pump and crankshaft oil galley plug backing out. Just seems to me that if it were either of these two it would have bad pressure all of the time not just once it warms up and the oil thins out. Maybe I'm SOL and it has a bad rod bearing?

I’ve ordered a new pressure sensor, but I’m not sure that mine is necessarily faulty since it registers such low pressure with a gauge hooked up to it.

I just wanted to see if someone had some insight or ideas on what else I should check. I think I’m going to try and at least change out the oil pump first because at least that doesn’t involve splitting the cases and see if that makes any difference. Thanks!

 

Replace the pump, and make sure you use the proper weight oil in that. I'm thinking the manual asks for 20w-50 or something?

 

Has the horizontal head been replaced on that motor? A lot of them have been replaced over the years from having issues and people LOVE to use RTV on those gaskets when putting them back together. Theres an oil port on the block to cylinder that gets clogged with RTV and can block oil pressure to the head (it destroys the head, I have one in the shop right now) and the RTV loves to fall back into the oil pump thats behind the clutch cover. Only fix is to pull the whole thing apart.

15w50 on most duc motors.

 

The oil pressure sensor went tits up on my old 2000 748; I think I've heard that it's not an uncommon issue with that vintage of Duc.

 

I have a new one on the way just to be sure ... but I had spare (leaking) one that I tried on it as well and got the same result. I was really hoping it was just the sensor but I'm afraid it's something worse.

 

It does look like it's been off for one reason or another - this thing has seen some rough time I think. It also seemed to have quite a bit of "piston slap" noise from that cylinder too that died down a little after it got warmed up but was still noticeable ... it may have also partly been "fin ring" since almost all of the little hockey pucks are missing. I just bought a used oil pump off of eBay and if that doesn't fix it I'll tear into it ... or put an 800 into it which is what I really want anyways. Thanks for RTV idea though ... I will definitely check for that when I have the pump off.

 

I know where there's a 2mm over 900ss motor with flat sides on it

I would pull the valve covers and check the insides of the heads. The one in the shop ran pretty damn well and the horizontal head had ZERO oil in it. The return springs on the opening rockers were all busted and laying in the head.

 

First thing I always check in that situation, the pressure relief valve in the pump. They get a bit of swarf in them, and stick.

 

I will definitely check to see if that valve is stuck (open???) on the pump that's in there now and the used one before I put it in. Thanks!

 

Toss that leaking sensor, too, otherwise the next stage of its leaking will be failure, indicated by the hot oil shooting up the inside of your leg, chest, neck, into your helmet and, ultimately, geysered onto the asphalt.
(Not tryin' to scare ya but...it's scary. Comes straight up out of the sensor in a solid stream of pain.)
Your other indication will be the red light showing on the dash.

 

Best fix for this problem:

EX500.

 

HA! Suck it!

I still have that thing too! ... Just to give Kurt hell in V5

 

HAHA! I hear ya! I did go ahead and order a new one just to be on the safe side ... I heard they were notorious for springing leaks like that.

 

Should have bought my 400, then you could have smoked him in V6LW too!

 

Oh I'm still kicking myself for that ... believe me. But, I'm glad to have a starter on both these bikes

 

A friend got lucky when his sensor blew..bike hadn't come up to temp yet and he wasn't on the gas. He got douched pretty good.
I noticed mine starting to leak after the first session of a trackday...I commenced making Margheritas. When I got home, I put a solid plug in it. The red light became an indicator of whether the bike was on, or not, which came in handy when I turned it into a race bike (push-button main switch).

 

Once I get the oil pressure resolved that might not be a bad idea to just plug it. I had planned on doing away with the key on this thing anyway in favor of a toggle.

So, if you don't have the sensor, did you just leave the sensor wire unhooked to keep the light on all the time? Or do you have to ground it?

BUT, I'm sure would kind of wig me out racing it with a big red light glowing in my face but I'd rather have that than it start spewing mid-race.

 

Left it unhooked. I didn't ground it, no need.

It won't take long to not notice the light when riding but, if you don't like it, you can always close the circuit at the connector.

 

This has been my experience as well.

 

Starters are for pussies. I can push an EX500 around the Road Atlanta pits on a June day faster than anyone!


(for about 20 seconds...)


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