carb tuning, running rich, bad needle jets?

[elbandtioCA]

i posted on here asking about ignition problems, but it looks like my problem is carb related after all.  the bike runs soggy in the mid range and after a little while the plugs are getting fouled.  i've been reading up about all the different carb tuning tips but the strange thing is that my main jets are smaller than others (87.5), i'm using stock needles, and it still is running too rich.  the bike has a yosh exhaust. from what i've read it sounds like damaged needle jets could be a problem affecting richness in this range.  what am i looking for in terms of damage?  is it easy to spot...or does anybody have a picture?  thanks.  (this is my first bike so i'm probably asking all these questions in the wrong order.)

[Banditmax]

Have a look for signs of ovalling in the needle jets.

[gsxr400 racer]

sound like the float orings are leaking amongst other things

[elbandtioCA]

hmmmm, i just replaced the o-rings and put new float assemblies in, new seals all around.

[gsxr400 racer]

ok what float height you using?

[PitterB4]

Yeah... float height would be a good thing to check.  How's the air filter?  Is it getting air?  Any weird obstructions? 

[gsxr400 racer]

  How's the air filter?  Is it getting air?  Any weird obstructions? 

Mice in there

[pmackie]

As others have suggested, start with the easier things first...

1. Make sure you have a new, clean, air filter
2. Check the idle air screws, and adjust them 1/2 leaner (not sure if that is in or out on a B4)
3. Check the float height, make sure it is at factory
4. Check the float needle valves to make sure they shut off/no obstructions.

Some other questions...
is the bike burning oil? Normally blue smoke out the exhaust. If so, poor performance and plug fouling can occur from bad valves/valve seals and/or bad ring seal.

[elbandtioCA]

i'm starting to wonder if it IS demonic mice in there...  no real signs of oil burning/blue smoke.  floats are at factory, but adjusting to lower fuel level isn't solving it.  i haven't had the bike long but i didn't put a new air filter on it.  would that make it foul plugs?  i'll go down the list you provide.  thanks

[PitterB4]

Yes!  Lack of air will foul plugs!  I've shared this before but...  One day I did some work on the bike (actually new plugs, I think)... put it all back together and rode to work.  Well, I forgot to put on the side panels.  My commute at the time was ~60 miles.  There is one nice long, uphill interstate stretch where triple digits are easy and pretty safe.  I was completely tucked and was wearing baggy cargo pants.  Without the side panels on, I had the airflow to the back of the box completely blocked.  My pants were getting sucked all around the box.  Running for several miles like that WFO fouled the plugs.  I couldn't figure out why it went from running GREAT to running like a total turd.  Fuzzy plugs! 

[elbandtioCA]

thats interesting--about running the bike without the side panels.  i've had mine off for the duration of all this trouble shooting, but the bike will start fouling the plugs just reving the engine at the right rpm while it is stationary.  but your story does make me think i should take a better look at the air filter/box situation.  thanks

[gsxr400 racer]

do you have the rubber plugs in the pilot jet holes?

[elbandtioCA]

i'm not sure.  what do they look like?  are they something that could fall out easily?

[gsxr400 racer]

if you turned them up side down they would look like little Abraham Lincoln rubber hats

[elbandtioCA]

hmmm, i don't see that part on the carb diagram that's in the shop manual or on the illustration of the pilot system.  i'll have to take the carbs apart--i had somebody else rebuild them.  what is their function?