I just swapped in new James gaskets on my 96 1200 Sportster. seems like everything is sealed up nicely except the rear base gasket. it leaks on the primary side at the rear corner immediately upon start up.

Here's the weird thing, it leaks on a cold engine but once it's warmed up it stops. hoping someone might know whats up here, I've taken it apart twice. the first time the leak was really bad. then took it apart the second time, torque it all down perfectly and it had greatly decreased on the second try.

thanks in advance for your responses!

 

Cylinders grow in length as they heat up. Sounds like that growth is closing up the leak. What style gasket did you use? Multi layer steel or the paper/silicone impregnated type. It sounds like your talking about the cylinder base gasket? Follow the proper torque procedure in the factory manual? YD

 

Might need to have the cylinder base trued... Cometic is the only way to go...

 

I built a new 124 engine using new parts, used james for the rocker gaskets (both support plate and cover), BOTH leaked in BOTH cylinders, ordered a new set of cometic to replace them.

I'm not saying that all of the james gaskets are awful (im using them in the primary to engine and engine to trans gaskets without leaks) but i'm very dissapointed with the rocker box gaskets, they look really well made but doesn't seal that well..

 

I'd suspect something going on the either torquing or that stud if it's the same place twice, those studs do stretch and once they start.....