Thoughts on 1 of 6 intake valves looking filthy?

[mstraub72]

Hello again all! Time to pick your collective brains. Quick update: Been slowly doing my first ever cam cover gasket replacement job, and have been taking it crazy slow and make sure everything is bang on spec. That whole entertaining saga is over at:

Little advice for first time Cam Cover Gasket replacement...I'm stuck

So, happy to report that yesterday was the turnaround point of the job...gasket was on, torqued it up in 5 little steps up to the recommended 10Nm max (vs. 12Nm the manual states), and then begun putting the whole schmozzle back together.

Curiosity got the best of me as I took my paper towel plugs out of the throttle body holes. Figured while I was here, flashlight in hand, I might as well see what it looks like down in there. 5 out of 6 intake valves looked great. The very rear one though...she's filthy. Bike ran like a champ, no stumbling, no smoke, no feeling of a missing cylinder, and all the plugs looked nice and clean, that proper cleanish brown you like to see on a plug.

So, this is what I see sitting beside the bike, where the throttle bodies are. Arranged and cropped the pics with Front / Mid / Rear cylinder headers.



What could cause just one intake valve to be so different? Anything I need to worry about? Should I maybe get hotter plugs (iridium?) and plop those in before I keep putting more of the bike together? Nothing makes sense to me...the rear throttle body feeds both valves equally in theory. Only ever used Premium fuel and Motul 7100 or 300V full synth oil. Even if one of the plugs was bad, would that mean that it's partially spitting unburnt fuel back up into the intake chamber? So weird...

 

[mstraub72]

Well, while I was finishing up my day driving around, I figured screw it, I'm already all the way in here, new plugs it is. Eliminate one possible culprit. So, in they go, then the rest of the cam cover reassembly ensues...

 

[dealer]

Hello again all! Time to pick your collective brains. Quick update: Been slowly doing my first ever cam cover gasket replacement job, and have been taking it crazy slow and make sure everything is bang on spec. That whole entertaining saga is over at:

Little advice for first time Cam Cover Gasket replacement...I'm stuck

So, happy to report that yesterday was the turnaround point of the job...gasket was on, torqued it up in 5 little steps up to the recommended 10Nm max (vs. 12Nm the manual states), and then begun putting the whole schmozzle back together.

Curiosity got the best of me as I took my paper towel plugs out of the throttle body holes. Figured while I was here, flashlight in hand, I might as well see what it looks like down in there. 5 out of 6 intake valves looked great. The very rear one though...she's filthy. Bike ran like a champ, no stumbling, no smoke, no feeling of a missing cylinder, and all the plugs looked nice and clean, that proper cleanish brown you like to see on a plug.

So, this is what I see sitting beside the bike, where the throttle bodies are. Arranged and cropped the pics with Front / Mid / Rear cylinder headers.



What could cause just one intake valve to be so different? Anything I need to worry about? Should I maybe get hotter plugs (iridium?) and plop those in before I keep putting more of the bike together? Nothing makes sense to me...the rear throttle body feeds both valves equally in theory. Only ever used Premium fuel and Motul 7100 or 300V full synth oil. Even if one of the plugs was bad, would that mean that it's partially spitting unburnt fuel back up into the intake chamber? So weird...

Looks like oil leaking past valve stem.

 

[Claviger]

That, or the inejctor pattern is biased towards the #1 valve on cylinder 3 so the back of that valve isn't getting washed.

All the DI cars have the same issue, but I suspect Dealer is spot on with his diagnosis.

Actually...something just occured to me... Do you still have the EVAP canister on and the stock intake setup?

 

[scot in exile]

Only use premium gas/petrol, money to burn you have

 

[mstraub72]

That, or the inejctor pattern is biased towards the #1 valve on cylinder 3 so the back of that valve isn't getting washed.

All the DI cars have the same issue, but I suspect Dealer is spot on with his diagnosis.

Actually...something just occured to me... Do you still have the EVAP canister on and the stock intake setup?

I have the RamAir kit, but still have the EVAP canister. I only know this due to the amount of rubber hoses I had to mark up while removing the Throttle Bodies. Haha...

 

[mstraub72]

Oh, and one other potential issue / culprit. As I said above, I grabbed all new plugs. Tossing them in now, and plug #5 (second most rearward plug, cylinder 3) doesn't have that assuring "zzzzzip" feel you get when you push the coil connection back onto the spark plug. It's pretty loose. The rest clipped onto the threaded tops of their new plugs nicely. Can a guy just get in there with some needlenose and try to squeeze the connection inside the rubber coil boot a little bit and tighten that up? Haven't messed with coils before, but each spark plug wire coming off the respective coil "looks" like it might just thread onto the coil itself, making for an easy replacement if necessary? It just has the look of a threaded piece. But, Murphy's law, it likely isn't replaceable and one would have to get a whole new Coil 3 if this is a problem. Again, bike never gave a hint of a stumble, or any error warnings on the dash.

 

[Claviger]

This bike has been on the market for quite some time ,he keeps listing it on ebay with a reserve(we all know what he wants for it) and comes no where close to it

Oh, and one other potential issue / culprit. As I said above, I grabbed all new plugs. Tossing them in now, and plug #5 (second most rearward plug, cylinder 3) doesn't have that assuring "zzzzzip" feel you get when you push the coil connection back onto the spark plug. It's pretty loose. The rest clipped onto the threaded tops of their new plugs nicely. Can a guy just get in there with some needlenose and try to squeeze the connection inside the rubber coil boot a little bit and tighten that up? Haven't messed with coils before, but each spark plug wire coming off the respective coil "looks" like it might just thread onto the coil itself, making for an easy replacement if necessary? It just has the look of a threaded piece. But, Murphy's law, it likely isn't replaceable and one would have to get a whole new Coil 3 if this is a problem. Again, bike never gave a hint of a stumble, or any error warnings on the dash.

Yes you can tighten down the connection safely.

I don't remember but isn't #9 here connected to the 3rd cylinder throttle body just next to the vacuum line? Just thinking here, it's very weird only 1 valve has gunk, I really, unfortunately think @dealer may be right on this one about the seal.

 

[Rocket Scientist]

My guess is the dirty intake valve has lost its clearance. As the face of the valve wears, the valve clearance tends to get smaller until the valve is actually staying open a tiny bit at operating temperature. This will allow the burning combustion gases to leak past and create that burned look on the back of the valve. I would be checking my valve clearances.

 

[Claviger]

He did, they're good.