how much does humidity affect jetting

[dirtyd]

This past weekend my R didn't run all that great. It was mid to uppers 70's but extremely  humid. I mean so humid that anything outside like paper or cloth would be damp just sitting outside, Iv'e never seen it that bad here. Bike ran great all summer and even at silver lake. It seemed to only do it when under a good load. When I noticed it I would be coming into a banked corner and when getting back on the gas it would sometimes stumble before it really got on the pipe and then would rip. If I was just ripping down a straight road it seemed to run fine. Just wondering if the humidity is what the cause is. I leaned out the needle one slot (from 3rd to 2nd notch form top) but didn't seem to make a difference. Also recently went from a NGk 9 plug to an 8, only because thats what I had. I wouldn't think going to a hotter plug would cause the problem but correct me if I'm wrong.
My set up
clean air filter
ESR 310 trx9 port
ESR TRX5 pipe
38mm A/S quad vent
50 pilot
175 main
not sure of needle but what ever came with carb when I bought it new, clip in 2nd slot

[Bowtie316]

I can't say how much but it will certainly lower useable oxygen in the air. For me it's usually temperature more than humidity that requires me to change jets, because it's almost always 70-90% humidity around here.

[Jerry Hall]

Humidity is measured two different ways....Relative humidity the number the weather forecaster recites and specific humidity used by the scientific community.  


Specific humidity gives a number of the actual mass of water per cubic foot of air without regard to air temperature or barometric pressure and can be used directly to determine the effect on jetting


Relative humidity gives a number that tells how much water can evaporate or how much water the air can absorb.  100% relative means that the air cannot hold any more water vapor and is temperature dependant.  There is a lot more water in the air if the relative humidity is 80% and the air temp is 90 deg than if the relative humidity is 80% the air temperature is 35 deg.

So what does the above information mean?

The effect humidity has on air density depends upon air temperature.  80% relative humidity at 90 deg F can necessitate a 1 to 2 jet reduction in main jet size while 80% relative humidity at 35 deg F will not usually require any change in main jet size