I think now the oil is leaking from the front main bearing. Is this because of the rubber sealed bearing or is there another problem?

I have 5 RB .15's ( one is a Collari, it is awesome!!! ), and I have noticed that some are messy and some are not. I heard a rumor that the front main bearing has been faulty in some of the X15's. I was told by Art Carbonell that my (brand NEW) X15 Collari had a leak in the front bearing when I asked him to help me tune it after I was having problems getting a reliable run at a recent major race event.

I replaced the bearings and the motor has since ran flawlessly.

I am a devoted RB supporter because all of my RB motors have performed excellent in the past, but I must say this last issue raises questions in my mind.

Now of course it can always happen that a bearing can leak some oil and if this is really excessif and your engine is still new or you are at the run-in process you could go back to your dealer or LHS to take a look at the problem and see if he can solve this for you.

Well, I raced today and being the stubborn SOB that I am, I kept inspecting the engine to try to trace he source of the leakage. It was in two places:

1) When I rotated the fuel nipple, I didn't tighten the nut enough so it leaked. Tightened; fixed.

2) The included manifold gasket had a tear in it. The bad seal caused leakage from the exhaust port. Replaced gasket; problem solved!

Sometimes, the easiest solutions are the right ones. Rody, thanks for the help. The engine is awesome and is very stable for a modded motor.