I have a 91 FLHTCU with 80k miles on it. I replaced all the gaskets on the top end, including head, and base, with new studs and bolts on the rear cylinder. Torque every think back to HD spec. Started the bike and let it warm up, rode it about 2 miles. Put it back in the garage and noticed oil leaking from the rear cylinder base gasket. Is it possible that there is pressure building up in the bottom part of the motor? I noticed when the cylinder where off that the motor was 1/4 the way full of oil, is that right? I replaced all the gaskets about 25k to 30k miles ago and had no problems until about 75k miles, when the rear srarted to leak a little.

Any help would be great.

Tom (krazyt)

 

Hi Tom from the UK and welcome to HDF. I have a 1990 FLHS owned from new. What you may be suffering from is that the faces of the crankcase and cylinder are not flat. These earlier engines have fairly small crankcase flanges, so any distortion in one or other can prevent a decent seal. It's the sort of job a competent indy should be able to put right, but may involve removing the cylinder studs from the crankcase, to ensure the top deck is flat.

For future reference we have a dedicated Evo forum, where you can meet fellow owners.

 

"91's were case breathers so I doub't your having a pressure build up issue. If you have oil being blown out the rear hose on the lower end of the motor, that's from oil leaking past the oil pump check valve. I'd bet that's where it's coming from. It will allow oil to collect in the crank case so when it starts, it slings oil around the crankcase and out the hose. That's an easy fix, you have to re-seat the ball in the check valve. Sometimes that happens when the bike sits for periods of time, sometimes it might be a speck of dirt. I'd start looking there.,,