Running rich but only on one cylinder.

mspenz

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These are out of a 02' single spark after 3k miles and the bike has done 36k miles overall.
When I have panniers fitted the box next to the silencer soots up quite quickly and that's how I first noticed it.
Bike runs well and gave me an average of 50mpg on a trip with a pillion last year so there can't be much wrong !

20190309_161741.jpg

I've changed the plugs, air filter, fitted a spare TPS I had, changed the injectors for a newly cleaned and balanced pair but the right side plug is still showing rich.
So...done a compression test and the results seem inconclusive ( for my limited knowledge anyway ).

LH cylinder shows 150psi with throttle closed and 215psi fully open.
RH cylinder shows 140psi with throttle closed and 205psi fully open.

Add a squirt of oil to the right side and it shows identical readings to the left.

Is that slight drop in pressure on the right pot enough to cause the dark plug, I thought that if they were within 10% of each other that would be considered as reasonably well balanced ?

New rings :nenau

Or is there anything I've missed ?

Mike.
 
i may be totally wrong but what about the thick rubber o ring on the injector ,one could be perished
 
fizzer said:
i may be totally wrong but what about the thick rubber o ring on the injector ,one could be perished
Click to expand...

All replaced along with the tiny strainers when the injectors were serviced.
 
Speaking of o-rings: Maybe the o-ring on the mixture screw is perished. Spray some silicon to protect o-ring on removal.
It would be worth cleaning out the mixture circuit. Remove vacuum take-off bungs before spraying carb cleaner.
Maybe some wear in the butterfly shaft. Though I'd expect the affect to be to lean the mixture. Maybe the ECU compensates and then you have too rich on one side.
Don't forget to drain the breather pipe oil in the air filter housing. (Not suggesting that's the prob)
 
All good solid suggestions.

The valve clearances are perfect as are the end float clearances, I need to check the balance again but it's running well with no abnormal vibration and the mirrors are smooth at idle...a good indication !

The RHS throttle body spindle was chattering when I got the bike so I changed it 5k miles ago.

Given that the compression is relatively even at matched throttle openings I can only assume that the air flow through the bodies is also even but it won't do any harm to clean out the BBS and housing, I'll also fit new o-rings but as already said that cause a weak mixture if anything.

The fuel pressure regulator is at a constant pressure ( 43.5 psi ) so each injector must have the same pressure, I changed the injectors after I started noticing the rich mixture so I'm wondering IF it's possible for the Motronic to send a wrong signal to one injector ( wrong pulsed ground signal for some reason ? ) :nenau.

I've heard it pinking on that cylinder a couple of times under load but that was before I noticed anything else wrong, it was also on the way home from Turkey last year so thought that it was just down to bad fuel and didn't think anything of it.

I don't have a GS911 and even if I did I probably wouldn't know what to look for on it :confused:

Mike.
 
I'd guess a problem with inj/ecu would be noticeable in poor running.
Is the plug grade correct? Are they Champions?
What about the timing. Any work on the HES? If you have a strobe light maybe worth checking.
On the bright side .. at least it's rich not lean.
Is there a possibility it's slight oil fouling rather than rich?
 
And it's probably an idea to have a good look at the HT lead and check the readings on the coil while I'm at it but other than that ..
 
Champion plugs initially but changed to correct NGK with the same results. If the timing was out ( unless it's cam timing ) I'd imagine that both cylinders would be affected, same goes for the HES but I could be wrong..and often am.
There's definitely a bit of a petrol smell at the back and no whiff of oil. My other 1150 ( a twin spark ) uses more oil and the plugs run clean.
I want to get it right as I have another trip to Turkey planned later in the year and would rather set off with a properly running bike :).
 
If it was me I would put in a new set of NGK spark plugs and run it for a bit. Then take them out after a good run and take a look at them.

You did say that the bike is running well and that you are getting 50mpg.

Looking at your photo, I would be more worried about the plug on the left which looks a bit on the lean side. The other plug doesn't look far off.
 
As I interpret your info,the Rh cyl is down on compression very slightly,and looks a bit rich.
There does not look to be excessive carbon build.so assume guides and rings ok.
Also assuming injectors ok ,intake ok,,your question is why is it rich on Rh cyl.
Why is it not getting enough air or is it getting more fuel.
Mebbs swap injectors left to right and run for a while.
Could you have a leaky valve?
Worth doing a cylinder leak test?
Not particularly conclusive I know,personally I’d pull the head off on the Rh side and check the valves,
After swapping injectors over
 
Smug said:
If it was me I would put in a new set of NGK spark plugs and run it for a bit. Then take them out after a good run and take a look at them.

You did say that the bike is running well and that you are getting 50mpg.

Looking at your photo, I would be more worried about the plug on the left which looks a bit on the lean side. The other plug doesn't look far off.
Click to expand...


Suppose the concern is the difference between the two.
 
Smug said:
If it was me I would put in a new set of NGK spark plugs and run it for a bit. Then take them out after a good run and take a look at them.

You did say that the bike is running well and that you are getting 50mpg.

Looking at your photo, I would be more worried about the plug on the left which looks a bit on the lean side. The other plug doesn't look far off.
Click to expand...

Already changed the plugs only to get the same fouling, the lighter coloured to me looks good and seems to be pretty standard for a GS !
 
JJH said:
What’s the oil consumption like? JJH
Click to expand...

Nothing to be of any concern and no smoke or smell at either start up or on deceleration to stop at a junction with a following breeze..if that makes sense :rolleyes:.

Somewhere in the region of around 900ml for 2200 miles I seem to remember.
I don't have a problem with that and at least I know to check it regularly and I always carry some on a trip, anyway, it just means that the engine gets some fresh blood between changes so definitely not a bad thing !
 
mikeyboy said:
As I interpret your info,the Rh cyl is down on compression very slightly,and looks a bit rich.
There does not look to be excessive carbon build.so assume guides and rings ok.
Also assuming injectors ok ,intake ok,,your question is why is it rich on Rh cyl.
Why is it not getting enough air or is it getting more fuel.
Mebbs swap injectors left to right and run for a while.
Could you have a leaky valve?
Worth doing a cylinder leak test?
Not particularly conclusive I know,personally I’d pull the head off on the Rh side and check the valves,
After swapping injectors over
Click to expand...

I've already swapped the injectors to another set cleaned and checked ( returned with flow printout ) from 'The Engine Tuning Shop ' so I know they are good, I also re-checked the resistance on both and they are matched.

A leaky valve / weak spring seems most likely but I don't have anything available to hand or know of anyone who could do a leak test so it will probably be a case of head off and see how things look !
That's my next little dilemma :rolleyes:. There's a very slight 'sweat' at the base of the right cylinder and although it's not enough to run or drip it catches all the dirt and bothers my OCD..so when I take the head off I might as well remove the barrel to seal the base properly and if I take the barrel off I might just as well fit new rings to that side seeing that when I add a squirt of oil and do a compression test the reading on the right then matches the left almost exactly :blast.

But..I can't start work on the cylinder until I finish work on the final drive of my other 1150, the bike is in the middle of the work space and I can't move it at the moment, final drive was removed with the intention of just replacing the main bearing but it needed considerably more than that as you know :D.

I'll get onto the cylinder strip down in a couple of weeks hopefully..

BMW stands for ' Bring My Wallet ' :comfort

Mike.
 
Cylinder leak down test being done later next week, be interesting to see the results.
 
You might just have a gummed up ring......oooer.
When was the last time the old girl had an Italian tune-up?
 
AberdeenAngus said:
You might just have a gummed up ring......oooer.
When was the last time the old girl had an Italian tune-up?
Click to expand...

Quite possible...I'll give my rings the heavy right hand soon :rolleyes:
 
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