carb tuning, running rich, bad needle jets?

[gsxr400 racer]

Keeps your plugs from instantaneously fouling out , they block the pilot or slow jet circuit which causes the pilot circuit to get its fuel on the bandit carbs from the main jet circuit, unlike the gsxr400 gk73a carbs.

[elbandtioCA]

so i just read another thread about the rubber pilot jet plugs and somebody suggested looking on bike bandit.  strangely, the schematic on bike bandit is slightly different than the one in the shop manual--it shows the plug as part #8, whereas the shop manual does not show any part here.  i wonder if the guy who rebuilt my carb, or a previous owner, was working from the schematic that doesn't show that part.  if those plugs weren't in, would the bike be fouling plugs at approx 5k rpms?  i take it that i need to take the carb off the bike and take it apart to check this out.

[elbandtioCA]

gsxr racer--thanks for this info--this is starting to sound like it could be the culprit.  the bike seems to run fine for a very short while and then the plugs are fouling quickly if it is in the mid range for very long. 

[gsxr400 racer]

yes you will have to take them off.

[elbandtioCA]

maybe i've got a "smoking gun": there were no rubber plugs in the pilot jet holes.  the needle jets may also show a little bit of "ovaling" but i don't have a sense of what normal wear looks like.  what is the cause of ovaled/worn-out needle jets (slides?), and should i be be replacing anything else while the carb is taken apart as a way to prevent the new needle jets from getting worn?

[gsxr400 racer]

will run rich as well , change the float needles and all the orings if you have not yet and get the rubber plugs you need.
cheers
 

[elbandtioCA]

hi gsxr400racer, i just updated the post i had in the general forum but i bet you know the answer.  i had already paid a mechanic to rebuild the carbs so all orings were replaced.  but he didn't check the needle jets nor did he notice that it was missing these plugs.  is that standard procedure?  he actually has the bike still, and the reason i found out it was missing the pilot plugs was because i went to his shop yesterday thinking i'd just settle the bill and get it home where i could open the carbs, but he had the carbs off the bike.  so i showed him the schematic that shows those plugs and we discovered it didn't have them. 

and thanks for all your help with this!  if you didn't mention those plugs i'd probably still be in square 1.   

[gsxr400 racer]

if he ordered the parts through Suzuki he had to have looked at a phish and they are on there, hope that fixes it for you.
cheers

[Herr Tod]

If you can see a small hole in the tube where the pilot jet goes, you need the plugs. If there is no hole (leading to the main jet) you don't need them. All of my 33 mm carbs have the plugs, they are all from a German Bandit 400. A 32 mm set I have, off a US Bandit 400, does not have the plugs and does not have the passage to the main jet.

[gsxr400 racer]

A 32 mm set I have, off a US Bandit 400, does not have the plugs and does not have the passage to the main jet.

If these are the ones you got from me then they are 32mm from a 88 gsxr400 gk73a

[Herr Tod]

They are, I didn't know a GSXR 400 had 32's ?

[gsxr400 racer]

They are, I didn't know a GSXR 400 had 32's ?

only in 88

[PitterB4]

If you can see a small hole in the tube where the pilot jet goes, you need the plugs. If there is no hole (leading to the main jet) you don't need them. All of my 33 mm carbs have the plugs, they are all from a German Bandit 400. A 32 mm set I have, off a US Bandit 400, does not have the plugs and does not have the passage to the main jet.

Really?  The 32s on my old US bandit had them.

[Herr Tod]

I was wrong, I thought they were off a Bandit but as said above they are off a GSXR 400 '88 model.

[elbandtioCA]

ok, so here's the update to my saga...and a question for the pro carb tuners on here.  i still didn't get my bike back from the mechanic.  he wanted to see it through by putting in the rubber plugs in the pilot jets, and by installing new needle jets, because the old ones showed some minor signs of ovaling.  he ordered the parts from suzuki. 

but today he called and said he'd done the work, but the bike is running very lean, even though he's basically rebuilt the carbs (as opposed to the rich/fouling plugs that it was before).  he was puzzled, again.  he said he put 105 main jets in because he didn't have the 102.5 jets lying around, and he said the air mixture screw is at 4 turns out.  when i bought the bike the prev. owner gave me a set of aftermarket jet needles that had been on there before he returned to the stock needles (i think they are factory pro), so my mechanic asked me to bring them down--he wants to try swapping in the aftermarket needles to see if he can get it running richer.

but then he mentioned that when he got the new needle jets from suzuki he was amazed at how much smaller the hole was compared to the old ones... and... he also noticed that the number was different than on the old needles jets.  but he figured that suzuki would know best...

so does it sound like a possiblity that suzuki provided the wrong part and now the thing is running too lean because the needle jets are the wrong diameter?  do any of you carb-masters know if there were more than one size needle jet available for these bikes, or would it be possible that suzuki just screwed up and provided one for a different bike?  i mean--would the needle jet from a different model of bike even fit in there?  at this point i'm getting exteremely frustrated by the whole process-especially because i get the sense that the mechanic might not be making the best decisions (like installing a part that has the wrong number and looks different)--that i'm supposedly going to pay $$$ for.  the advice i've gotten on here is very valuable to me--without gxr400racer's tip the mechanic wouldn't have even caught the pilot plug problem.  sorry for such a long post...as i said, this has turned into a saga