Got a 1990 FLST which hadn't been serviced in a while. There was a slow leak which came from the primary case. Wiped clean and watched it leak from the lower two bolts and the drain plug (very dark oil). Drained the primary and oil was black. Replace main case gasket, and other cover gaskets. Replaced the drain plug with new. Added ATF-F fluid (red) about 30 oz. Also changed the motor oil and filter. New Plugs. Started the bike and saw leak, pretty fast drip. Shut off bike. All primary case bolts clean and dry and no evidence of leak. Drain plug clean and dry no leak. Red ATF fluid leaking from somewhere behind the primary. Did I over fill the ATF oil? It mst be forced out from somehere? Where's it coming from? Thanks for the help.
Primary Oil Leak
- Thread starter DonW
- Start date
BUBBIE
Well-Known Member
Probably the inner primary seal... Clean good behind the primary and look up between the inner primary case where the shaft come into it.
Cleaning the case,then running it should show you where the lube is coming from.
Why use that Light ATF?
I would Not use an automatic fluid in a primary
Get Rid the ATF unless it is an AUTOmatic...
If you use a heavier weight OIL for the primary LIKE Formal+ or another one like MTL by redline, you Might Not leak.. If this bike has set for a long time, IT Might need time to seal again WITH the proper lube...
signed....BUBBIE
I agree, it sounds like the seal dried out from sitting. You might get lucky after it get's some use and stop leaking, cross your fingers.
Just thinking out loud here. You might as well replace those trans seals on the primary side while you are in there. I chased an primary oil leak for a week only to find it was a trans leak.
I have an outer primary off of a Softail out in my garage that was replaced by a dealer because it was leaking through the casting. So don't rule that out either...........................as far as the ATF goes you'll get lots of contraversy on it, I use it and my bike shifts much better than with formula + due to the fact that the clutch plates release instead of sticking together.
So here's what I discovered. Took off the primary cover again and found one of the middle inner primary bolts backed half way out and several others loose. Figured that bolt was the source of my leak. Followed the youtube videos and took out the compensator and clutch pack and seals looked good. (By the way you need some serious sockets and big leverage bar to get those nuts off). Took inner primary bolts out one at a time and reinstalled with RTV and proper torque. Refilled case with wet clutch rated20W50. Drained transmission fluid and replaced with new. Fired it up and not one drop! Had a beer and started on installing turn signals which had been removed. That will be another post as it looks like whoever worked in the primary also had a hand in the wacky wiring. Thanks for the help and comments.
Thanks for getting back with the solution. Unfortunatly some will work on things without knowing what they are doing. If you run into any more problems that have you scratching your head there are many members here that have been in the same place and will be glad to help. Ride Safe, Don