Is it normal to have exhaust pressure under your valve cover?

[outlawbusa]

We had head work done a while back on one of the bikes and ever since installing the head there has been a clicking noise we have been unable to track down.

We have had the cams out at least 20 times checking valve clearances, cam chain, swapped tensioners, etc, etc and yet to track down this noise.

The bike runs great and picked up power on bottom end but lost a couple mph on top end once the head work was done. We had decided to pull the head back off over the next couple days and go ahead and replace the cam chain and a few other parts...however tonight may have changed some thoughts.

We took the cover off once more and started the engine with the cover off. There is a strong exhaust pressure coming out of the head into the valve cover area. This may be the noise I have been hearing.

Is it normal to have some exhaust pressure into the valve area, I would think this would pressurize the case also? If not, would I be looking for a valve that is not seating properly? Head gasket not sealed properly?

Since it started the second this head was installed I would think there was not enough time to damage anything like a burnt valve, especially since the bike still runs like a champ.

Anyway, should know a little more in a couple days...what are your thoughts?

 

[mikepeavler]

Sounds like you have a leaking valve and or springs may need to be a tad tighter to follow the cam profile if you swapped them. Some pressure is normal...hence the pair garbage on top...however nothing like what your talking.

M

 

[Commuta_Busa]

sounds like either a valve or valve seat issue.

 

[smac]

Could also be the head gasket leaking pressure back into the engine or even a cracked head. Are you sure the head you got back was actually your head? Just a thought...

 

[outlawbusa]

After speaking with a local buddy it appears to be possibly a normal discharge with the valve cover off. There are 4 holes/tubes that go through the top of the head and normally into the pair valves or block off plates. Once the valve cover is off this pressure is able to shoot straight up instead of into the pair valve.

Thoughts?

 

[smac]

Ticking noise could be an exhaust leak. Try using an engine stethoscope to pinpoint the noise.

 

[JGGUNS]

I assume you have done a compression and leak down test? That will tell you if you a valve not fully closing or a broken copression ring letting blowby into the case.

 

[mikepeavler]

A small fraction amount of air is normal...but nothing what I'm reading sounds normal about your situation. I run block off plates on mine and keep in mind you have a crank case breather so there should be an "out" for any internal air that is formed. I'm still thinking you have a leaking valve if your air is excessive.

 

[outlawbusa]

I believe we got it taken care of...ticking is gone now. The leak down test came back looking great on all cylinders.

We shimmed a little tighter towards tighter end of spec this time. Pressure looks good, nothing at all coming out of the breather.

Went for a short spin across town last night and the Bad A sound it used to have is back again

Ready to roll~!~