Oil On Throttle Body & Rich Right Cylinder

[Adamski1100]

HI all, ever since I bought my R1100 GS (99 - 30k miles), it has had a noticeable petrol (rich running) smell when stationary. I have serviced the bike, and swapped out the plugs which looked like originals, and to my surprise they were a completely different colour, the right cylinder black with carbon, the left plug looked much cleaner. I replaced the plugs, and also the injectors for a set of 1200 Tills injectors, and immediately the bike started better, idled smoother, and seemed a lot happier, however, when I pulled the new plugs I spotted the same result, carbon on the right plug, left plug much cleaner. I have carried out a compression test which has shown both cylinders are virtually identical, and give good readings. Over the weekend, following a ride of some 45 minutes, I happened to put my hand on the bottom of the TPS plug, and ended up with some oil on my hand.

Could this contribute to the differences in running between the left and right cylinders? Where would be the best place to start to diagnose? Check the airbox for oil and for any cracked or leaking breather lines?

 

[Riceburner]

Just so I'm understanding correctly..... errrr (how to put this)....

Which left and right are you using? Normal convention is to use the viewpoint of "sitting on the bike", then applying left and right. I ask because it sort of sounds like you're using the viewpoint of "facing the front of the bike" - in which case left and right would be reversed from the normal convention.

I'm mainly asking because "traditionally" it's the left cylinder which can get blacker oily plugs more readily - so if it really is the right side plug that is oiling up - then we can negate a few potential issues.

As reference - the Throttle Position Sensor (TPS) is on the left cylinder inlet manifold. (unless I'm massively wrong!)

 

[Adamski1100]

Just so I'm understanding correctly..... errrr (how to put this)....

Which left and right are you using? Normal convention is to use the viewpoint of "sitting on the bike", then applying left and right. I ask because it sort of sounds like you're using the viewpoint of "facing the front of the bike" - in which case left and right would be reversed from the normal convention.

I'm mainly asking because "traditionally" it's the left cylinder which can get blacker oily plugs more readily - so if it really is the right side plug that is oiling up - then we can negate a few potential issues.

As reference - the Throttle Position Sensor (TPS) is on the left cylinder inlet manifold. (unless I'm massively wrong!)

The oil residue on the bottom of the throttle body is on the left side as you sit on the bike.

The black spark plug is from the right side of the bike as you sit on it, as if the right cylinder is running rich.

 

[Riceburner]

The oil residue on the bottom of the throttle body is on the left side as you sit on the bike.

The black spark plug is from the right side of the bike as you sit on it, as if the right cylinder is running rich.

ok - cool - that clears things up immensly! I'm going to treat them as separate issues then.

My guesses would be:

Black plug on RHS would be either a fuel-ratio issue, or a spark issue: first thing to try would be a new plug - or just clean the plugs and swap them. If the blackening swaps sides, it's the plug, if the blackening stays on the right, it's something else. Perhaps the coil or just the plug lead would be the next things to check.

Oil on the underside of the TPS would be a weep somewhere on the head/rocker cover - you may be able to trace it back to source. My money would be on a weeping rocker-cover gasket - maybe the inner seal is malformed or not in place - that's an easy thing to happen when you replace the cover after checking the valves. Also - did you absolutely dry off the mating surfaces of the rocker cover and the head? I've always found that ANY trace of oil on those mating surfaces or the gasket itself will cause a weep when the rocker cover gasket is replaced. (I once inadvertently left a trace of blue paper caught up in the underside of that mating surface - got a VERY oily boot on the next ride...)

 

[Adamski1100]

ok - cool - that clears things up immensly! I'm going to treat them as separate issues then.

My guesses would be:

Black plug on RHS would be either a fuel-ratio issue, or a spark issue: first thing to try would be a new plug - or just clean the plugs and swap them. If the blackening swaps sides, it's the plug, if the blackening stays on the right, it's something else. Perhaps the coil or just the plug lead would be the next things to check.

Oil on the underside of the TPS would be a weep somewhere on the head/rocker cover - you may be able to trace it back to source. My money would be on a weeping rocker-cover gasket - maybe the inner seal is malformed or not in place - that's an easy thing to happen when you replace the cover after checking the valves. Also - did you absolutely dry off the mating surfaces of the rocker cover and the head? I've always found that ANY trace of oil on those mating surfaces or the gasket itself will cause a weep when the rocker cover gasket is replaced. (I once inadvertently left a trace of blue paper caught up in the underside of that mating surface - got a VERY oily boot on the next ride...)

I fitted new plugs recently and have run through a couple of tanks of fuel, same result unfortunately almost identical to the plugs I replaced. Left plug still looks relatively new, right plug already has a coating of carbon. I will try and dig out my Carbtune tool to see how the balance is left to right.

Looking again at the oil residue on the underside of the throttle body, there doesn't appear to be any leaks from the rocker cover / head, it appears to be coming from a small allen head bolt on the underside of the TB, the cable running to the TPS sits beside this so I guess the oil has run down that. So i assume its a breather system issue, or a build up of oil in the airbox.

 

[GORILA]

The oil on the left cylinder could well be from the camchain tensioner bolt. It sits on the cylinder just behind the throttle body. Often just nipping it a little tighter will solve this issue.
There is an updated version. This has a 15mm hex bolt versus the original which was 17mm.

 

[Adamski1100]

I removed the airbox oil drain plug after a ride last night, with the bike on its side stand, and roughly half a teaspoon came out. I will run the bike a bit more and give it another drain to see if there is any difference.

 

[Adamski1100]

Finally found where my Carbtune was hiding, put it in such a sensible place I struggled to find it! Anyway, the balance at idle looks pretty good, but on throttle the right cylinder gives significantly higher values, I will adjust this weekend and see what happens! I also noticed while crouched down on the right side of the bike, it absolutely stinks of fuel / exhaust, so i wonder if I also have a small header leak on that side.