ratl wrote:
If I understand correctly, when the temperture drops, the fuel amount going into the manifold at a given throttle setting remains essencially the same while the amount of air increases due to a significantly higher change in density relative to the gasoline. So, except for the shot of gas from the accelerator pump, the ratio at a constant throttle position is too lean.

Sound like the easiest solution for a temporary basis is to open the pms a bit.

Or, I am I out in left field?

Not at all .... elegantly explained.

It would be best to completely rejet for wide swings in temp but the PMS trick works quite well. The circuits overlap so a slight increase in fuel at the low end seems to do the trick.

Doc

I know right now I should turn my PMS IN and lean the bike out a tad because I am running rich, now if I wait for it to warm up, it will be fine and if it gets really hot, I will be running lean.
Which is the reason for an ADJUSTABLE MIXTURE SCREW IN THE FIRST PLACE...

Yes.

That's essentially why you should always rejet at the temp at which you do most of your riding. That way you can use the PMS to slightly offset the effects of temp.

Doc

EFI

DocShadow wrote:
ratl wrote:
If I understand correctly, when the temperture drops, the fuel amount going into the manifold at a given throttle setting remains essencially the same while the amount of air increases due to a significantly higher change in density relative to the gasoline. So, except for the shot of gas from the accelerator pump, the ratio at a constant throttle position is too lean.

Sound like the easiest solution for a temporary basis is to open the pms a bit.

Or, I am I out in left field?

Not at all .... elegantly explained.

It would be best to completely rejet for wide swings in temp but the PMS trick works quite well. The circuits overlap so a slight increase in fuel at the low end seems to do the trick.

Doc

OK Doc, wanna pick your brain a little. Where I am at the average summer temp during the day is upper 90's and eve summer temp in the low 70's upper 60's. Winter day temps average upper 40's to mid 50's and eve temps range between high teens and upper 30's. Now with such a high differential in summer and winter temps as well as day and night temps (usually about 30 degrees) where and how would I even begin to figure out a median jet setting so that I can rely primarily on PMS tuning for compensation in the fuel/air mixture? Sorry for the long question.

the truth is you guys wwwwaaaaaay over think this stuff
On any given ride on any given day the Temp will vary 10 to 15
degrees the elevation could vary from 2000 ft to 9000ft.And the
Humidity maybe slightly

Which is why you find a nice general "close" setting on the"CV"carb
and go Ridin! BOO YA

MY HEAD HURTS! but, this IS a very interesting thread.

That must be why my road*s been running kinda rough the last time i went out 42degree

It would be very interesting to know how much adjustment to make for temperture swings of say, 20, 30 and 40 degrees.

Lets say it turned out to be a quarter turn out for every 20 degree drop for instance, it would certainly make it easy to set up for a ride without a lot of frustration on the ride. We have temp swings of 30 - 40 degrees as the norm from morning to day to evening here. This would be great information to have.

Anyone have any thoughts on that?

Well, Being from the Yamaha of Warren area, I know for a fact that Ken who owns the shop and has a stellar reputation in community as best shop in tri state area, He says he runs em a little rich in winter and maybe I should not say, but he even adjusts mine back for free in spring even though the screw is in a bear of a place to get to. But I am long time customer who always goes there for parts and gives him a shot to beat any price I find on the net, 9 out of 10 times he does.

So yea, run richer in winter.

Last winter mine ran like crap because of leaking intake, but this year it ran exceptionally perfect when they set it up for winter. It's like 60 here and I can tell it's running too rich now. So I'll be going in for the free while I wait adjustment. And did I mention he has free donuts and made to order coffee machine too?