Leaking cylinder head

[dub 24]

Hey folks
I was checking my stick coils today and on removing said stick coil I had exhaust gases escaping through the plug hole. I am amateurily assuming I have a cylinder head that is cracked . If anyone can offer advice etc I would be very grateful
Cheers
Dub 24

 

[AberdeenAngus]

Have you checked the plug?

 

[dub 24]

Cheers Aberdeen Angus, yep I tried another plug and it was the same.

 

[Cyrano]

Cheers Aberdeen Angus, yep I tried another plug and it was the same.

Could be a leaky plug-hole gasket , and what you feel is probably the "breath" from the sump. I reckon a cracked head would provoke more severe symptoms.

 

[dub 24]

Cheers cyrano unfortunately what I didn't put in my initial post was that the bike was coughing spluttering and backfiring which led me to think I had a stick coil problem.
Cheers
Dub 24

 

[mspenz]

Would be unusual for a head to crack, can you see or hear something when the engine is running ? I'll probably get shot down for this but maybe try removing the stick coil on that side ( earth it using a spare plug ? ) and then start/run the engine on the secondary lower plugs...this way you will be able to look into the spark plug tunnel and see if there's any gas escaping from around the main plug.
It's also another way to check if your coil is failing, try starting it with only the primary's connected , if it doesn't start or run then try just with the secondary plugs connected...or disconnect a secondary on each side one at a time ( only briefly )..if the engine cuts out it's likely to be the coil stick on that side.

Use new plugs or torque one that has been tightened more than a couple of times to 20Nm and re-check for a leak.

 

[mspenz]

Also to add, I had a problem with a backfiring bike a few years back, it ran fine until it was under load and it turned out to be the stick coil breaking down but it would only show up under load.

 

[dub 24]

Would be unusual for a head to crack, can you see or hear something when the engine is running ? I'll probably get shot down for this but maybe try removing the stick coils ( earth them using spare plugs ? ) and then start/run the engine on the secondary lower plugs...this way you will be able to look into the spark plug tunnel and see if there's any gas escaping from around the main plug.
It's also another way to check if your coil is failing, try starting it with only the primary's connected , if it doesn't start or run then try just with the secondary plugs connected...or disconnect a secondary on each side one at a time ( only briefly )..if the engine cuts out it's likely to be the coil stick on that side.

Use new plugs or torque one that has tightened more than a couple of times to 20Nm and re-check for a leak.

Hey mspenz
Thanks for the reply I have ran the engine with the stick coil removed and running on secondary plugs and the gases were indeed coming out of the spark plug tunnel, I did this because when riding the bike yesterday and trying to accelerate I was getting serious coughing, spluttering, and a initial pause in power/ acceleration followed by full power in acceleration. Would you have an idea what the issue is and what is causing the gases to escape through the spark plug tunnel
Cheers
Dub 24

 

[mspenz]

Hey mspenz
Thanks for the reply I have ran the engine with the stick coil removed and running on secondary plugs and the gases were indeed coming out of the spark plug tunnel, I did this because when riding the bike yesterday and trying to accelerate I was getting serious coughing, spluttering, and a initial pause in power/ acceleration followed by full power in acceleration. Would you have an idea what the issue is and what is causing the gases to escape through the spark plug tunnel
Cheers
Dub 24

I'm just learning as I go, much like yourself..maybe worth spending on a compression tester before going further ?

 

[dub 24]

Hey folks
We pulled the head of the cylinder and couldn't see anything obvious. I am going to delve a little deeper and take the rocker/ camshaft holders off and check the valve and seats for any obvious cracks etc. One thing we did notice was the bolts holding the cylinder head at the bottom weren't as tight as the rest and are wondering if this could have caused the issue. If anyone has any advice or suggestions please shout as any help it always appreciated.
Cheers
Dub 24

 

[tadhgocuilleain]

I might be way off on this but there's a hole/channel that runs from the exhaust header through to the plug hole. Is it possible the header isn't sealing properly and is blowing exhaust back through that hole?

I saw your earlier thread about getting the exhaust studs off. Is it possible something got damaged in the process?

 

[dub 24]

Hey Tadhg thanks for your reply there is a cylinder head cover gasket/ seal but I think it's only an oil seal. As regards the exhaust studs that's on the other bike I am rebuilding this is my daily commuter . One BMW isn't enough to cause stress I have to have 2.
Cheers
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[Steptoe]

Stop panicking and replace the spark plug tunnel seal.

And when you fit it make sure it's on the rocker/valve cover, do not push it into the head and then replace the rocker cover, you'll squash it and get a sound like a cracked cylinder head

And if testing the stick coils you leave them in place and remove the lower secondary plugs and see if the engine runs on both (or any) cylinders..

 

[dub 24]

Cheers steptoe have a new seal ordered
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