Bad gas mileage

[zz28zz]

This all started in 92-93 when I had a Kerker 4 into 2 header installed and the mech re-jetted the carbs. Uni-filters were also installed at the same time.
Mileage went from ~47 to ~29 mpg. Bike seemed to run ok but the pipes are looking pretty sooty. Plugs are a light tan color.

Bike was stored for a few years and I'm now trying to get her back up and going.
Pulled the carbs for a serious cleaning today and made notes of what I found.

Float level measured .94" on all carbs (spec= .84-.91") Measured like this: http://www.fjowners.com/index.php?topic=6580.0
air jet= 160
low speed fuel jets= 37.5
main jets= 124
idle mix screw= 2.25 turns out
Needle= next to top slot

The float level being too high would translate to fuel level in the bowl being too low, which would make it run lean correct??

The other question mark is the needles. They have multiple slots which makes them aftermarket, right??
I didn't see any markings on them, so I'm not sure what they are. Is there any way to identify them?

Same thing for the needle jets, not sure if they are original or not. Any way to identify them?

Any other thoughts on why the mileage dropped so much??

Thx
John

[yamaha fj rider]

There are those who are better with jetting than I am but here we go. Pilot jet should be #40, you called this a low speed jet. Mixture screw about 4 turns out. I think the 124 main jets are to big? I think you are lean to 1/4 throttle and rich above that. If there are no marks on the needles or needle jets you are just guessing at the jetting. You can adjust what you have but still not know what it is. I would replace these with the right stuff. You can keep messing with these and never get it right. Call Randy at RPM tell him what you have (exhaust, air filter) he will fix you up. Spend a small amount of money once to get it right. Hope this helps? 
http://www.rpmracingca.com/

Kurt

[zz28zz]

I was looking at the emulsion tubes on Randy's site and noticed he sells e-type tubes. My tubes don't have the cut-out on the top.
Does the cut-out make them e-type?
Do they enhance atomization?
Did the 84 carbs come with e-type tubes??

Noticed the needles in the carb re-build kits are brass colored, mine are silver. Does this necessarily indicate they are non-Mikuni??

Also, I don't see Mikuni 124 main jets being offered on any of the sites I checked. Maybe they're Dynajets???

Sorry abt all the questions at once. Just trying to figure-out what all I need to get.

[racerrad8]

I was looking at the emulsion tubes on Randy's site and noticed he sells e-type tubes. My tubes don't have the cut-out on the top.
Does the cut-out make them e-type?
Do they enhance atomization?
Did the 84 carbs come with e-type tubes??

Noticed the needles in the carb re-build kits are brass colored, mine are silver. Does this necessarily indicate they are non-Mikuni??

Also, I don't see Mikuni 124 main jets being offered on any of the sites I checked. Maybe they're Dynaj

ets???

Sorry abt all the questions at once. Just trying to figure-out what all I need to get.

E-tube is for emulsion tube.

The flat bottom slide uses an un-shrouded e-tube as well as a shorter main jet needle. The picture on my website is not the correct e-tube for the 84.

The brass needle is a replacement for the OE aluminum needle.

If you have 124 jets they are probably dynojet jets which are rated differently from the Mikuni which are the listed on my website.

Randy - RPM

[zz28zz]

Thx Randy. That clears up a lot. In regards to the "E-type" tubes statement, I was going from memory. Must be getting old 
I saw a Dynojet/Mikuni jet size conversion chart online. Looks like the 124 Dynojet converts to approximately a Mikuni jet half way in between a 115 and a 117.5 cc/min. I suspect I'll need to drop main jet size to a 115, or maybe a 112.5..

Once I get the carb o-rings installed and the fork seals replaced (that I ordered from ya), I'll start road testing.

[RichBaker]

A 124 DJ main is WAY too rich. I have 114s in my '90, with D&D pipe, UNI pods. Sounds like everything else is pretty close, though.

[andyb]

Sounds to me that someone went with a comically rich main jet and then set everything else quite lean in an effort to smooth things out some.  IMO, I'd pretty much start over.  A 115-120ish mikuni main jet, bring the needles to the middle, air jets to 155, and set the float heights to spec.  The emulsion tubes (needle jets, e-tubes, etc) should also be checked for ovaling/wear, and replaced if there's any question.  From there, you'll have to do some fine tuning, but things should be fixable.