Originally Posted by augerpro
So How does the crankcase keep from sucking air? No bubbles came from anywhere else.
I believe it is the tight tolerance between the crank journal and the case that keep it from sucking air. The chances of the engine sucking air from the front bearing are pretty slim and if it did it would not be because of the seal on the bearing, it would be because of a worn out crank journal. Bearings are not air tight! Engines made for RC boats sometimes donít have but a metal shield on the front bearing and they donít suck air! If you really think you have an air leak here are places to look & seal up.
1. Tank, tank lid and fittings
2. fuel lines
3. Fuel filter.
4. Seal carb to case with RTV
5. Seal back plate with RTV
6. Seal pinch bolt with RTV
7. Seal fuel inlet on carb around banjo.
8. If necessary seal carb boot at both ends
9. Make sure all the o-rings on all adjustment needles are in good shape and not loose in there housingís.
10. Make sure head bolts are tight
11. Make sure your exhaust gaskets are making a good snug fit and are not torn.
I know some of these things are obvious; I just listed all the things I could think of that might help. Does the engine idle well and for a long time?