I'm still getting some coughing into the air box when it's not warmed up fully. What's that? It doesn't seem to have any flat spots at any rpm's just the coughing, strong smell and lousy mileage.
Really want to get this figured out since I'm a little hesitant to go on a long ride with such bad fuel consumption.
Just too clarify the 90's or 100's should be paj1 which you can see from the top.
The 170's are paj2 behind the slide diaphragm.
The bigger these are the leaner you are.
Coughing spitting up through carbs is typically a lean condition. Lean conditions usually improve as bike warms up. Opening up the a/f screws will usually help this. But will also make your idle smell even stronger.
For fuel mileage sake I don't mind mine spitting a little till the bike is warmed up, as long as its not to an embarrassing degree.
Also, if the vboost is open at idle the spitting up can be exacerbated.
One clue that the vboost is open at idle is if you've got a particularly awesome sounding lumpy idle that sounds like you've hot huge cams. Vboost closed it idles much smoother. . .
If your af screws are only out two turns which is pretty lean already you could also try installing 90's in the paj1 spot to cure that spitting but the af screw is a more direct way to address the spitting, neither are going to help your fuel smell by going richer to cure the spitting tho
The fuel smell and the coughing spitting are opposing issues since one is a rich condition and the other is a lean one. Kinda makes it hard to sort out.
Honestly tho with your jetting it oughtta be just fine and there's probably a real problem somewhere.
If all your jets are as you say they are your mileage should be better for sure. Any stock vmax oughtta make a solid 35-42mpg when just cruising and highway riding, around town very spirited riding low 30's isn't terrible. Really wailing on it a lot can yield high 20's
Possible problems?
Float level too high?
This will cause lower mileage too, the higher the level the less vacuum in the venturi's it takes to move fuel from bowl to carb throat.
Slides sticking open?
(Usually this one will be accompanied by all sorts of nasty behaviour that's super annoying, chugging, refusal to take throttle etc) this can be checked by using a screw driver and opening the slides all the way and quickly releasing them, they should return rapidly.
Needles not dragging on needle seat?
This can cause the slides to stick) Improperly assembled slide/ needle assembly. Properly assembled the needles should have some wiggle to them so they don't drag on the walls of the needle seat tube causing the slide to hang.
Bowl drain screws not leaking?
This could account for the wet boots. Were they wet on inside or out?
Floats needle/seat not sealing well? (This can be diagnosed by how long the fuel pump runs after the 1st or 2nd time you turn the key on without starting it) once the bowls are full you should be able to come back in 5-10 minutes and turn the key back on and not have it click more than once or twice if that. If it clicks more then the bowl level is leaking down somewhere. Having cut your fuel filter open was a good move too for evidence of a tank problem.
Main jet backed out and loose? ( I've had em fall out completely before when I was being too delicate during assembly trying not to strip anything)
Believe it or not with one main having fallen out it wasn't terribly obvious riding it, just when idling since it would load up and want to die from too much fuel.
Same goes for the screw on the jet block that holds the needle seat tube. (That breaks really easily by the way)
Missing jet block rubber plugs? (Yep, I've done that too)
Jet block not seated adequately against gasket? ( had this happen when I put too big an O-ring on the main needle seat tube before installing the jet block, it feels tight but the block wasn't seating against the gasket
Missing o ring behind the slide covers?
this ones easy to do, at least for me. They fall out right before you install the cover sometimes. I'm not sure what the symptoms of this are.
Cracked or improperly seated boots?This would make a lean condition, accounting for the carb spitting but just the opposite on fuel smell; UNLESS they are making you so lean the cylinder won't fire therefore expelling the unburnt fuel.
I honestly don't think vboost makes a lick of difference open, closed or out of adjustment. I've run mine in lots of different configurations and other than a bottom end response loss on off idle if open too early or all the time, the ET's and mileage did not change appreciably.
If closed all the time you're of course going to lose power up top but it shouldn't run badly, just slower.
If you have the carbs off you should be able to play with that switch and figure out a little bit about it by watching the vboost mech and feeling of the butterflies.
(Don't chop your fingers off!)
All that being said I don't remember my vmax ever not smelling like rich exhaust except when it was bone stock, and maybe a little bit even then.
If your idle speed is right and its firing on all cylinders synch is probably ok, obviously if synch is so far off that one cylinder won't fire it's going to blow raw fuel since that cylinders is still going to get fuel from the orifices in the carb that are downstream of the butterfly. If idle is right and synch is way off the cylinder with the closed butterfly may not fire at all.
If you don't have an ear for it then checking the exhaust pipe temp is a good way to detect cylinder firing. If one is colder then you can crack it open a little at a time till it does start firing to prove it out. Checking for equal temps is rather difficult with the stock exhaust. An infrared temp gun is handy for this.
Another thing you can do is check the plugs making sure they look normal, then just let it idle as long as you can where you smell the fuel. Might need an extra fan on the radiator. Do this for a while never letting it do anything but idle and then check the plugs.
Might tell you a little but no promises there.
