Idle Surges From a Leaky Valve Cover

[Msiert]

Just a heads up when doing a valve lash adjustment. When you put the valve cover back on use a new gasket making sealant to seal up the valve cover to the head.

It has been a number of years (7) that I had done a valve lash check so this week I did it. The last time I did them I set the intake at .004 and the exhaust at .006 and after 7 years they changed to .006 intake and .008 exhaust.

After the change back to .004 intake and .006 exhaust I took it for a test ride and after about 10 min of riding the idle started to surge and than drop so low it would stall out. But after adjusting the idle screw up (quite a bit) and giving it a lot of throttle on the way back I was able to get home without doing the walk of shame.

The next morning I took off the valve cover that I didn’t use any gasket seal on (relaying on the old sealer) and check the valve lash which had not changed and than I reinstalled the valve cover with a RTV Blue gasket maker and took it out for a test drive later that afternoon and didn’t have any problems.

There must have been enough air leaking through the old valve cover gray caulk gasket to cause the idle surges.

 

[Tony01]

Just a heads up when doing a valve lash adjustment. When you put the valve cover back on use a new gasket making sealant to seal up the valve cover to the head.

It has been a number of years (7) that I had done a valve lash check so this week I did it. The last time I did them I set the intake at .004 and the exhaust at .006 and after 7 years they changed to .006 intake and .008 exhaust.

After the change back to .004 intake and .006 exhaust I took it for a test ride and after about 10 min of riding the idle started to surge and than drop so low it would stall out. But after adjusting the idle screw up (quite a bit) and giving it a lot of throttle on the way back I was able to get home without doing the walk of shame.

The next morning I took off the valve cover that I didn’t use any gasket seal on (relaying on the old sealer) and check the valve lash which had not changed and than I reinstalled the valve cover with a RTV Blue gasket maker and took it out for a test drive later that afternoon and didn’t have any problems.

There must have been enough air leaking through the old valve cover gray caulk gasket to cause the idle surges.

Just a coincidence. Intake more likely.

 

[Venice Motor Bikes]

The only way that a leaking valve cover could cause an idle surge is because of a worn intake valve guide. Or maybe (if your engine has one), the little rubber intake valve oil seal that goes right below the valve spring.

 

[Msiert]

Today the 4G tranny with a 10 tooth output sprocket came in and I switched out my 4G with a 12 tooth output with it, had to take a link out of the chain to get it to work.

Took the bike out for a test ride afterwards and it did surge for a little bit and died a couple of times but after playing with the idle speed screw it went away, so you guys were right!

I‘ll check the carb attachment to the head to make sure the carb bolts are snug.

 

[Sidewinder Jerry]

Today the 4G tranny with a 10 tooth output sprocket came in and I switched out my 4G with a 12 tooth output with it, had to take a link out of the chain to get it to work.

Took the bike out for a test ride afterwards and it did surge for a little bit and died a couple of times but after playing with the idle speed screw it went away, so you guys were right!

I‘ll check the carb attachment to the head to make sure the carb bolts are snug.

On my Robin Subaru 35, I switched the Phillips head screws to torx head screws. This way I can use a small torque wrench to set the cover screws.