I changed the oil and filter and replaced with Harley oil, 20w50 and a new Harley filter. I rode about 1 hour to Erie and after a couple hours I started back. Everything was fine on the way out. The oil pressure was about 35 pounds at 2300 rpms. The outside air temperature was 62. The bike is a 2008 Ultra Classic that started life as a 96 cubic inch and was later bored out to 103 with a mild cam. On the way home the oil pressure started out at about 35 pounds and after about 15 minutes it slowly started decreasing. I made it to my HD dealer in about 30 minutes and by the time I got there, the pressure was down to about 17 pounds at 2300 rpms. I had some oil indication problems in the past and they changed the pressure sensor twice to no avail. I left it at the dealer and when I checked on it they said that they had ridden it twice for 10 minutes each and could not find anything wrong. One tech said that 15 lbs pressure is "completely acceptable" on these motors. My problem is the slowly decreasing oil pressure. After some discussion they said they would put there pressure gauge on it. Any suggestions?

 

I know the hotter the oil gets the thinner it gets so it can drop.. What's it at idle hot?

 

sometimes as low as 3lbs depending on the out side air temp

 

Hook up a mechanical gauge and monitor oil pressure!

 

Hi Troy
That is what the dealer said they would do today. The problem is they may have to ride it for quite a while to get it to do the same thing it did for me.

 

I am new to HDs , but almost every engine I have seen act like this in past , had issues with worn bearings , or an oil pump going south.

 

Oil viscosity thins as it becomes warmer, and will show up in the high-volume, low-pressure HD system.
Scott

 

As I said , new to Harleys. I do understand that oil thins out as it warms up , it just weirds me out that oil pressure drops as low as it does in these things.
I'm used to seeing this happen as bearings , etc wear , and clearances increase. In every other engine I've owned , the problem was solved by replacing bearings , and/or the oil pump.
Mine does the same thing, and it still makes me nervous.
Scott

 

Just a quick update. When I had my cams done , they made an adjustment at the relief valve and the pressure doesn't drop as low as it did
Scott.

 

The TC system is designed to be a high-pressure system as compared to an EVO, or Shovel for that matter. These older systems were low pressure high volume. Every TC I have owned has ran close to 40-45 PSI at cruising speeds of 70 and 4,000 rpm's and from 15-25 at idle....depending on the temperature and the model-year, or modifications made (meaning the larger oil pump or adding an oil cooler). I would be truly concerned if a tech told me that operating pressures of around 15 were normal on a Twin Cam.....it isn't. If it's down to 3 at hot idle, unless I happened to be riding thru Death Valley and the temperature was 115-120...that would also be of serious concern.

Here is the part that would really make you nervous. The service manual I once had for the EVO instructed one to set the idle just high enough for the oil-pressure light to go out. Back in those days, when guys were revving-up their engines on a hot day at a traffic stop, they were not showing off....they were trying to keep the oil-pressure warning lamp extinguished. Mechanics usually balked at the idea of installing an OP gauge on an EVO. All it would do is scare you to death anyway.