CO2 query

Windmill John

Windmill John

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My 2000 850 GS has suddenly started using a lot more petrol; just had new injectors and a hall sensor.
I was at the dealers on Saturday and they tell me my CO2 is way too high.
He said there was not enough adjustment in the CO2 sensor. He's adjusted best he can and we've booked it in for next week to look at it again and possibly the air temp sensor, in case that thinks it is colder than it is and is enriching the mixture.
My confusion is, bearing in mind my knowledge of normally aspirated bikes is very good, I haven't got a catalytic converter or lambda sensor. I didn't know I had a CO2 potentiometer.
So what does he mean?
Is it a computer adjustment through the CPU?
Any help?
Where is this potentiometer?
Cheers
 
If its like the 1100.the CO2 pot is accessed from under the rear mudguard,on the offside near where the ECU is.You are effectively tweaking the mixture through the ECU (CPU).If the dealer cant adjust it via the pot,it does sound like there is a problem elsewhere and he seems to be on the right track with the air temp sensor (in airbox).Other things to look at are TPS voltage and check for dirty air filter.
 
You want the CO (Carbon Monoxide) presence in the exhaust fumes to fall in the range from 1.5 to 2.25%

If they couldn't get the range right then they should have checked the temps sensors then and there it takes 5 minutes!

The one in the top of the airbox and one under the fuel tank at the right hand upper side of the engine

I think that your bike has an information display does the temp gauge read app 5 bars when warm in traffic? If so you can pretty much rule out the engine oil temp as thats where the ecu takes the engine temp from

The airbox one is only a matter of swopping one off a mates bike to test changing airbox lids is even better Less risk of breaking something!

Now the other question and I can't remember what a 4 gas analyser has on it since it's soooo long since I've used one BUT I think it's CO, O2, HC and Is it CO2?? If they are trying to set CO2 take your bike off them and run away very very quickly!
 
Thanks for the responses guys,
Hold on to your hats, my CO2 reading was 7!!
They got it down to about 4, ran out of adjustment, but did not have enough time to check other sensors.
I don't know anyone else with a GS locally, so am taking the gamble of leaving it with them to sort out. I am getting 45-50 miles per tank less over the last couple of weeks!!! I cannot afford that.
I know what I'm doing with my Honda Dominator and older bikes, they are normally aspirated.
I have to say I was tempted just to order an air temp sensor, but if that wasn't the fault, it would be a waste of money. Looks like the dealer can spend my money instead:(

BTW, no display for temp on my bike, no ABS, just High beam, indicators, charge, oil and neutral.
 
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Been there, done that... I also have a an R850GS. Mine started to run very rich. I therefore swapped my potentiometer (CO adjuster) with a used one from Motorworks - the range on this was much wider than that on my original one- tested with ohm meter. That gave me some improvement. Likewise swapped the oil temp sensor for a used one - again did comparative test of range, using boiling water to test cold and hot readings. Again, replacement had more noticeable range. Never bothered with air temp sensor. These changes had some effect, but what finally cured it was resetting the TPS to around 0.370 mv. This tranformed the bike and removed all surging. I now have nice coffee-coloured spark plugs and reasonable fuel consumption (52mpg). It's never been brilliant on this front because it is so low geared, so I have to thrash it. :D

Hope this helps.
 
Thanks guys,
Enjoyed the surge PDF.
Trullion, I'm unsure how to check the TPS setting and as I use this bike every day for work, need to make sure I get it right in short time.
Move to East Sussex, bring your multimeter with you, I'll ply you with tea and biscuits and we're done:)
After reading what you wrote, I am a little tempted to purchase a oil temp sensor, but as mentioned, if I do this, I wouldn't know where to reset the CO2 sensor to and could end up running very weak; certainly don't want to do that.
I might have to admit defeat, it's just the cost of repairs is so high. I like the dealer, but they are a main one so rates are high.
 
Thanks Tony, fantastic TPS document.
I'll have to wait until the weekend, but let's see how it goes.
I do have a multimeter, just never used it much on the GS.
Helped troubleshoot my rectifier on my old T3 though.

Does anyone have the settings for the air temp sensor?
 
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The older motronic on the 850GS doesn't 'learn' the throttle position, so the opening and closing of the throttle isn't necessary for this purpose, (though see below). You should pull fuse 5. What I do is peel back the rubber connector, stick a pin through the rearmost (red/white) wire and connect the +ve lead to the pin. The -ve lead I clamp to earth; it's easiest to connect to the side stand spring (in the down position). Switch on ignition, but don't start. Make note of reading (so if you have to you can reset to a known point). Then adjust to 0.370mv. I find that you have to re-adjust slightly after giving the throttle a few twists to settle it. Off hand I can't remember which way the adjustment moves when you tighten the screws, but I find that you can allow for this, so that when the adjustment has been made, you switch off the ignition, and then switch it on again to recheck the setting it then stays put. A bit like doing up locknuts on valve adjustments, if you see what I mean. Anyway, it worked for me. I was so pleased with the result that I adjusted the one on my 1100RS as well.

Sorry, I can't help with actual resistance values (at least not here, still at work). I simply compared mine to a used one from Motorworks cause I was looking at relative changes rather than absolute ones - they said they were happy to have it back if it didn't do the trick. Might be worth giving them a call.

Good luck.

I'm going home now :)
 
Thanks Trullion, I hope you're back at work now:)
One last question.
Over the last couple of days, my tick over has gone down to 500 RPM, so I'm booking to tomorrow off to check everything.
Do I assume that it would be best to get my tick over back to standard before I set the TPS, as 500 RPM would probably give a wrong reading to the exact position of the butterfly?
I know exactly what you mean re tappet adjustments!
Really appreciate everyone's input.
 
you don't have the engine running while setting the TPS, and the butterfly is not moved when adjusting tickover.
 
Thanks for that.
I knew not to have the engine running, but I, old fashioned wise, assumed the idle adjustment would push against the butterfly, holding it slightly open; I'm obviously wrong on that score?
 
Windmill John said:
Thanks for that.
I knew not to have the engine running, but I, old fashioned wise, assumed the idle adjustment would push against the butterfly, holding it slightly open; I'm obviously wrong on that score?
Click to expand...

idle is adjusted with the bypass valves (brass screw heads in throttle bodies). do not touch the throttle stops unless you particularly want to spend ages setting them up again ;)
 
Marvellous!
Let's see if swearing is involved tomorrow:)
What I want, is to buy a new bike, with the tolerances of a new bike, so no oil leaks, but with points, normal tappets, normal carbs and a shaft drive. Kick start and electric.
I know about emission laws, but hey!
 
don't worry, it's all pretty much as easy as setting up an old bike...



...as long as you've not touched those throttle stops :D


i think you might want to read up on one of the "how tos" here or on ADV rider ;)
 
i think you only need the full zero=zero malarky if the throttle stops have been tampered with.

if the factory paint is still on the adjusters, i'd start at step 5 and set TPS to 0.385 which i've found to be a sweet spot for 1150s.
 
Yes, DON'T muck about with the throttle stops; you'll only introduce another variable. I've never adjusted mine on either of my oilheads. As has been said, the engine shouldn't be running when you check and then adjust the TPS. Strictly speaking it's best to adjust the valve clearances first, but here we're talking about solving rich running rather than doing a tune-up. So if it works you can then give it a good service. Just to be clear, when you made the connections as I said in my earlier post re-connect the connector, then switch on the ignition (don't start the engine) and take the reading. Then adjust to around 0.370mv.

For the record, mine was so bad you could see soot blowing from the exhaust when the engine was warm, and it reeked of petrol, though it ran alright. If the TPS adjustment doesn't do the trick (and the air cleaner is clean) you could try replacing the oil temp sensor - this is to be found behind the alternator on the RHS of the crankcase, under the tank, next to the oil cooler union. If you remove it and measure the resistance (ohms) cold, then stick it in boiling water and re-measure, you should see a change. I don't have the actual measurements - I just compared mine to another, used one. Personally I doubt that it is the air temp. sensor, though I understand the logic of why it could be. There's not much to go wrong with it, unless it has been damaged. I once forget to re-connect mine after replacing the air filter - can't say it made much difference. Still, changing it might be worth a go. The potentiometer affects the mixture at the bottom end, but if you do a lot of traffic riding it will influence fuel consumption more. I couldn't get mine to have any noticeable effect on mixture strength. When I replaced it with a used one that had a much larger adjustment range (ohms again) I was then able to adjust the mixture strength. The real improvement in my case, however, came from adjusting the TPS.

Good luck
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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