View Full Version : 1984 FXRT Primary Oil Line Question

07-04-2017, 1:14 AM
Hello Everyone.

I recently purchased an 1984 FXRT with a pulled cylinder stud. In addition I purchases a 1990 EVO motor to replace the 1984 motor. I swapped out the motors and was running the oil lines and started to discover some issues I can't seem to find a good answer on.

Please see below diagram of oil line routing on the early model 1984 FXRT.

https://cimg0.ibsrv.net/gimg/www.hdforums.com-vbulletin/529x381/80-oil_line_routing_d33107a4cbf6bc50f9ef59b7730d7dbf3 c08136a.jpg

There are two oil lines that go into the primary. One is a "T'ed" off line from the oil pump going up the the oil vent tube. The other is routed to the engine case separate from the engine case breather vent. . The issue I am running into is the 1990 EVO motor does not have that oil line attachment on the engine case as the original motor cases had.

I have done some reading about isolating the primary. I believe I could do this rather easy but reviews on the longevity of the fix are mixed. If I did do this and needed the vent the primary how would you do this. In addition since I have a dry clutch in there if I fill the oil just to the bottom of the clutch basket will it be okay or will my clutch go bad.

The other question I had was if I wanted to keep the oil system that is in place. Instead of running the line back to the engine cases could I run the line and "T" it off to an existing oil line? Perhaps the feed line from the oil pump into the oil filter?

Thanks in advance for you assistance.

07-30-2017, 10:53 AM
I believe the 90 breaths through the heads while the 84 was a crankcase breather. This would mean that the engine breathes through the two holes in the cylinder heads where the air cleaner mounts and into the air cleaner. The 90 had a separate crankcase vent line that will run to the air cleaner.

I would also seal the primary

07-30-2017, 2:03 PM
I dislike dumping breather oil into the air filter housing and on my 1994 FXR I don't connect the hollow bolts to the (S&S in this case) filter housing. No issues with suckback into those little tubes and I'd have noticed on the dusty roads I often ride on.

In the days when men were men and sheep were nervous, cars had road draft tubes and breather caps but emissions regs mandated positive crankcase ventilation. Motorcycles often have more crankcase pressure issues than cars and I hate oily elements or spark plugs as an engine ages so when it's my bike the only thing going into the air filter housing is outside air.