Hello, I have 2 O.S. powered vehicles, Revo (18TM) and HPI RS4 (.18CV-RX). First of all, I love my O.S. engines. They hold a tune very well and hardly go through any glowplugs. My problem is "stuff" leaking from the front bearing. By "stuff" I mean I don't know what it is. I notice a line of dirt on the body that is directly in line with the front of the engine as it's being slung outwards from the force of the engine. I can only assume that it's fuel leaking. Both engines do this and neither have any problems. One thing the .18TM does different is around the dust boot on the carb slide I see "stuff" gathered around the end. Like I said, both engines are running fine, this is more of a nuisance than anything. I have sealed both engines to the best of my ability. This is the only part I don't know how to fix. There may not even be a fix but I need to know if there is a way to stop it. Thanks!!!!

When nitro fuel burns, not all the oil burns. Most of it comes out of the exhaust but I think it's only normal that some comes through the bearings
This is why nitro cars are "messy" and need more cleaning than electric

My OS does the same thing
Unless we both stuffed our engines [X(]

I can remember my 3.3 and the original motor for the RS4 not leaking at all. I'm wondering if it is a problem with O.S. engines. I have read some more posts like mine saying they have the same problem. I also wonder if other manufacturer's have the same problem.

It is absolutely normal for some oil to come out of the front bearing and be thrown from the drive washer or flywheel. This will leave a stripe under the engine and on the body. That small amount of leakage is needed so that the front bearing gets lubricated. If there was no leakage you'd have a problem. The only problem would be if the leakage was severe enough that lots and lots of raw fuel was being thrown from there. That would be that the fit of the crankcase to the crankshaft is bad. Remember, the front bearing does not provide any kind of seal. The seal is made by the close fit of the crank and the crankcase between the carburetor and front of the engine.

Well, that's the best explanation I have gotten so far! Thanks for clearing that up for me.