Lean mixture when turing / leaning during riding

[Bradley.Isaac]

Hello Fellow GSers,

Usually there is enough information on here to find or piece together an answer for whatever question I have. It seems like every question I ever have has been answered several times already. However, I cannot find anything about my new issue.

When riding, right hand turns cause a lean mixture and left hand turns cause a rich mixture. What could cause this?

Some background...
'83 GS850G with stock airbox and 4-1 exhaust.
New orings on intake boots, new intake boots, new intake boot bands, carbs twice fully disassembled and dipped (told by mechanic who saw them thew were the cleanest they had ever seen! ) ,all new orings in carb, new rubber plug over pilot jet, new airbox boots, new airbox boot bands, airbox weather sealed, clean airfilter, valves adjusted, compression tested 130-145 psi, vacuum tested petcock (put 10inHg vacuum using a hand pump on the fuel port. Still had full 10inHg after 24+ hours with no fuel in line between petcock and handpump)

I am in the process of tuning my carbs now that I have preformed my due diligence. To aid with tuning I have a MTX-L Wideband O2 Gauge installed on the bike. The gauge does outline a simple procedure for calibration but I don't have any illusions about the accuracy of this gauge. All decisions about changing needles/jets are made after a plug chop. So even though I don't trust the gauge for absolute readings I do trust its relative readings. For instance, if the gauge reads 12.0 and then changes to 18.0, I trust that the mixture has become more lean. Not necessarially that the mixture was at those absolute values.

So when I am cruising along at 1/8 to 1/4 throttle (aprox 13.5 on gauge) and go into a sweeping right hand turn the bike looses power. At the same time the gauge has gone to 18/20. So these air/fuel readings are likely not the true ratios but I do believe that something is happening when I turn that is causing the ratio to lean out. When I turn to the left the gauge reads 10-12 and I regain power. During normal "straight up" riding the bike has lots of power and the plugs all look okay. I don't know if I could maintain a right hand turn long enough, since i have such weak power, to color the plugs and get an idea if maybe one cylinder is not firing. Does a cylinder not firing even make sense? Wouldn't that leave an excess of fuel and indicate rich on the gauge?

This happened to me the other day after several hours of riding and again today after at least an hour on the bike. Between these two occurances I have changes both the main (120 to 117) and pilot jet (45 to 42.5). I have shimmed (radio shack washers) the needles leaner (from 0.5mm to 2.0mm). I have adjusted the float tang using clear hose to verify the fuel level. Set at 5mm below edge of float bowl.

I don't know what this could be. Since I have changed so much with jetting between occurrences I would think that none of those items would be the culprit... Any ideas?

I hope I haven't drudged on too long with too much detail. Thank you for your time and any help you can offer.

Cheers,

[ender22]

um, off the top of my head:

1: Are the float needles clean and free moving? Do they stick open when you lean the carbs?

2a: try taking the corner with the bike perfectly vertical and use your body to lean, Results?
b: Try leaning the bike over while going in a straight line, Results?

3: check the float levels

4: Does it lean out when the petcock side of the tank is up higher?

5: Is there something in your exhaust that's moving around?

6: Is the ignition coil working properly when angle or with G force applied?


All in all I like #6 as the long shot cause. Hopefully it's something else.

[pdqford]

Does a cylinder not firing even make sense? Wouldn't that leave an excess of fuel and indicate rich on the gauge?

That'a a common misconception. If there is a misfire, yes, there is excess fuel in the exhaust, but the gauge is not a fuel sensor, its an oxygen sensor. It sees the unused oxygen from the misfire and reports it as a lean condiction.

[OldVet66]

Making a turn shouldn't cause a loss of power. I suspect your float levels are borderline and would check that they are correct and verified with a visual float level tube before over analyzing the situation.