the great wave of xshead

[southerndime333]

i have a stupid question for all you crazy cats... i know how much you love them, =D

ok here goes... i took the head off my 1979 xs... right next to the valve springs on the intake side.. there is a wall like thing why is it there??

right there that ive marked in black , thanks to 650 motorcycles

 

[DirtyErnie]

My guess: oil control. Acts like a dam to divert more oil to the hotter Exhaust side of the head to help cool the valves and springs over there. Picture how the oil would get thrown around with that cam spinning a couple thousand RPM.

 

[southerndime333]

Do the exhaust valves get hotter than inlet??

if that wall wasnt there more oil could get around.. cool things alittle more ?

 

[DirtyErnie]

Do the exhaust valves get hotter than inlet??

if that wall wasnt there more oil could get around.. cool things alittle more ?

Quite a bit hotter, with all that exhaust gas blowing around the stems and heads and guides an' all...

That looks like the kind of thing that wouldn't have been done if there wasn't a need for it. I just think about that camshaft spinning up to 3,500rpm and the kind of oil that would be flying around in that space.

 

[littlebill31]

The oil would also get caught in there and be unable to circulate back though the engine if it were removed. It would also fill up around the valve and go into the intake/exhaust if the shoulder was not there. That would be bad.

 

[southerndime333]

The oil would also get caught in there and be unable to circulate back though the engine if it were removed. It would also fill up around the valve and go into the intake/exhaust if the shoulder was not there. That would be bad.

i understand now, cheers guys.... i wasnt going to cut the walls off ... just wondering why they are there...

 

[XSLeo]

There are oil drain holes by both intake and exhaust valves. This prevents excess oil build up around the valves.
Having the wall does throw more oil around the exhaust valve which will help cool the valve.
If you wonder which valve gets hotter ride your bike a few miles, touch the carbs then touch the exhaust see which one burns your finger.

 

[xjwmx]

There would have to be drains on the other side of it, otherwise it would fill up eventually and be there forever. Actually, there should be a jet of oil shooting at the end of the valve. Don't know that there really is, but there should have been if there isn't.

Most of the time a valve problem will be the exhaust valve. It gets hot exhaust products going past it, but the intake gets cool gasoline going past it.

 

[littlebill31]

I was thinking there was a little port, but couldn't remember.

 

[XSLeo]

On the head in my lap, by the exhaust valves there is a low ridge between the valve and cam. At the outside by the cam bearing seat is a groove to let oil drain away from the area under the cam. The cam chain tunnel lets oil drain from this area too.
The drain holes by the valves are drilled just above the spring seats.
The drains by the exhaust are about 5/16, the intake are about 3/8.
With the wall deflecting oil away from the intake and the groove sending oil from under the cam and the smaller drain hole it keeps more oil a bit longer around the exhaust valve, this cools the valve area a bit more. This flow of oil under the cam is how the cam bearings get oiled. The area under the cam is about level with the bearings seats. The oil under the cam builds up deep enough som some runs into the cam bearings.
On the rocker arms, oil is sent to the rocker arm shafts and rocker arms under pressure. There is a hole in the rocker arm that squirts some of this oil to the cam where the rocker arms ride. Oil gets thrown all over the cam chest by the rocker arms and the rotation of the cam and the oi thats carried up by the cam chain. This thrown oil is what lubes the valve stem/rocker arm contact point and some gets into the cam bearings.
I would say that most of the oil to the top end comes up as spray from the cam chain.
I hope this answers the questions you have about oil flow in the head.
Leo