Won't start and now air pushed out of breather

[pablohoney]

I recently rebuilt my 79 650 special and it was running just fine, started right up and ran great for a while. But the other day, it was idling and just died. No warning, sputtering, just died. It won't start with starting fluid. When I kick it over air is being pushed out of the breather tubes. This sounds pretty detrimental. Is it?

 

[pablohoney]

Never mind just a fuse. But is air supposed to come out of the breather?

 

[Tomterrific]

Yes.

tomterrific

 

[retiredgentleman]

Sure, with the pistons going up and down as they are prone to do, air will pulse in and out of the breather. I like the way Yamaha designed my 78SE................both hoses from the breather go into the air box. The air with a very small amount of oil mist is recycled back into the cylinders and is burned. Works perfect.

 

[pablohoney]

Cool, good to know thanks.

 

[XSLeo]

As RG said as the pistons go up and down they move air. The same amount as gets moved above the pistons.

This air needs to go somewhere. If it just compressed it would blow out seals. That makes a real mess.

They designed the breather to relieve this pressure.

As the engine runs oil gets thrown all over inside the engine. Some of this oil becomes a mist and moves out with the air. The early bikes just ran a hose to the bottom of the bike or into the hole in the right side cover to let this mist lube the chain. The hose would get a film of oil on the inside and as the pistons move up and air gets drawn back into the engine, this oil film will catch most of the dirt from the outside air thats drawn back in.

Later bikes hooked the hose into the intake so this mist wasn't blowing all over the road.

Some folks put a Power Brake Check Valve in the hose. This valve is a one way valve, it lets air out but not back in. This creates a vaccum inside the engine. It helps prevent minor oil leaks and helps the rings seal better.

Some just put a small filter on the end to prevent dirt from getting back in.

Leo