Oil line Sizes

Hey PSF,
I've only been messing with kz's forba while, BUT I have messed with cars most of my life. -8 is closer to a 1/2 from what I've found. When your stringing trans cooler lines on a hotrod, and you're using the steel braided stuff I know you usually use -6. I dnt believe the -8 will allow for enough line pressure. Try the oil pressure gauge and see what you have, but you might also try some -6 hose.

jp-15 wrote: Hey PSF,
I've only been messing with kz's forba while, BUT I have messed with cars most of my life. -8 is closer to a 1/2 from what I've found. When your stringing trans cooler lines on a hotrod, and you're using the steel braided stuff I know you usually use -6. I dnt believe the -8 will allow for enough line pressure. Try the oil pressure gauge and see what you have, but you might also try some -6 hose.

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Im running 6-AN fittings with 3/8 " hose. 8-AN is way big, and uses 1/2 " dia hose. I think 1/2" hose is to big, could cause a pressure drop?

I'm not quite sure I understand. You say you think that 5/16" is to big, but you're using 3/8" (6/16"). I believe -6 should be alright for oil cooler lines on a bike. Then again, I've got minimal experience with this on these motorcycles. I would just think that if I use -8 on my racecar for the oil cooler with a HPOP, that -8 would be like a garden hose to the kz with a LPOP. Obviously, the smaller the line, the more pressure you will have. In theory. You need to find a happy medium between volume and viscosity.

I have a 13 row Earl's cooler with Earl's -8 hose and fittings on my little 1105 motor, and I have never had a problem with my oil light coming on.

jp-15 wrote: I'm not quite sure I understand. You say you think that 5/16" is to big, but you're using 3/8" (6/16"). I believe -6 should be alright for oil cooler lines on a bike. Then again, I've got minimal experience with this on these motorcycles. I would just think that if I use -8 on my racecar for the oil cooler with a HPOP, that -8 would be like a garden hose to the kz with a LPOP. Obviously, the smaller the line, the more pressure you will have. In theory. You need to find a happy medium between volume and viscosity.

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ya, my bad its 1/2 " hose if you use 8-AN not 5/16.

The proper way to check the oil level in a bike with a cooler is to stop the engine, put it on the centerstand, wait 10 minutes, then check. Add oil to bring it to th proper level.

I have the oil level/amount part taken care of. But i wondered about the lines. i could try reducing the line size. Its just weird that the problem started after a cooler swap. I had the old cooler with the same line on there for over two years with no problem. Then i added a one row larger cooler and now i got a light. But i will try to get a gauge sometime. Does anyone have a decent used one they would like to get rid of decently cheap?

Powerstroke_fan wrote: I am having some problem with my oil pressure light after a bigger oil cooler install.

First question: how is your cooler plumbed into the system? I've seen some bikes with the cooler in parallel with the oil system (oil is taped off near the pressure switch and returned somewhere like the oil fill plug, but the stock oil transfer pipe is left in place). In this case it may be possible for the cooler to cause a loss of pressure in the head/cam by stealing to much oil volume away from the pump.

Most people put the cooler in series by replacing the stock oil transfer pipe with two hose barbs. In this case all of the oil that flows through the cooler then passes on to the head. A loss of pressure in the cooler would cause a loss of pressure in the head. But bigger lines and a bigger cooler would both reduce the pressure lost on the way to the head, making the system better. With this setup smaller hoses should be bad.

Second, where is your oil pressure switch. The most common setup has the switch located before the input to the cooler. So any pressure lost through the cooler would not even be seen by the pressure switch. The switch would always see full pressure.

I also think the pressure switch is really more of a flow switch. I seem to recall the switch has a disk that plugs the oil transfer pipe, and the disk is pushed up when oil flows around it. If not enough oil is flowing the disk would not be pushed up far enough to close the switch contacts. Can anyone confrim this?

Is there any chance the new cooler or one of the lines or fittings is plugged or pinched?

I was reading this and wonered if maybe your old system was working but borderline too big so when you put on that bigger cooler, the added cross-section of the cooler was just big enough to reduce your pressure to the point where now it is triggering your light. You shortened your lines but maybe it wasn't enough to compensate for the added area in your cooler. Beings you only changed the cooler, it seems the only thing it could be is the extra volume of the cooler resulting in a loss of pressure. This is interesting beings I'll be adding a cooler to a bike this spring and the cooler you have is about what I will need. Can you increase the pressure in the system some way? I know when a turbo is added, they used to put in a little bit stiffer spring in the oil pressure swith behind the engine to compensate for the extra volume and to feed the turbo.

Iam not sure on the stiffer spring racer54. But i agree that maybe my lines are too big. Iam running oil cooler bypass fittings that replace the stock switch.piece with a two piece set up. The switch is still in the factory location tho, which is before the cooler. Thats why the light was throwing me off before because i thought pressure dop in lines shouldnt affect the light. but i guess with the drop in the lines its just not enough to open the switch fully. Anyways i will be ordering smaller lines friday to see if this fixes the problems. i will probably be going with -6an size line.