Bandit Alley
MODEL SPECIFIC => SUZUKI BANDIT 250 & 400 => Topic started by: elbandtioCA on January 09, 2008, 07:53:44 PM
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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.)
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Have a look for signs of ovalling in the needle jets.
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sound like the float orings are leaking amongst other things
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hmmmm, i just replaced the o-rings and put new float assemblies in, new seals all around.
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ok what float height you using?
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Yeah... float height would be a good thing to check. How's the air filter? Is it getting air? Any weird obstructions?
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How's the air filter? Is it getting air? Any weird obstructions?
Mice in there :shock:
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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.
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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
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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!
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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
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do you have the rubber plugs in the pilot jet holes?
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i'm not sure. what do they look like? are they something that could fall out easily?
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if you turned them up side down they would look like little Abraham Lincoln rubber hats
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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?
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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.
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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.
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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.
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yes you will have to take them off.
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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?
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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
:beers:
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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. :thanks:
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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
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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.
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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
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They are, I didn't know a GSXR 400 had 32's ?
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They are, I didn't know a GSXR 400 had 32's ?
only in 88
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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.
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I was wrong, I thought they were off a Bandit but as said above they are off a GSXR 400 '88 model.
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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
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or to make matters short: does anybody know the part number the needle jets that should be on my bike (it is an american bandit with 32mm carbs)? that way i can check myself to see if suzuki ordered the wrong size. my shop manual says that american gsf400s have a size "0-9" needle jet, but if i recall correctly there was a long series of numbers etched into the side of the jet. now i just have that sinking feeling that my mechanic got the wrong part and installed it.
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Download the manual. All the carb specs are listed, including diagrams.
Stock settings for your bike would have been
MJ 102.5
JN 5EZ74
NJ 0-9
He should be able to get it to run RICH with the jet kit installed... on the right (or wrong clip) it will foul plugs in a couple of blocks.
Does he have the air filter installed??? After sniffing gas all day sometimes you forget the easy shit... LOL.
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hey interfuse...i'm not sure of the numbers on the jets he just installed. if they are the wrong part, i won't know unless i (or he) opens it up again. but lets say he put in the wrong NJs and they are too small, making the bike run lean. would using the aftermarket needles, on the right clip position, be a decent way to fix the problem--to compensate for the leanness? or is this just "treating the symptoms"? if the only proper solution is to install the stock NJs (0-9) then that's what I want him to do--it doesn't seem right to try these half-ass solutions like playing with aftermarket needles. but if both ways lead to the same result, then i guess it isn't a problem. i just don't know enough about carb tuning to know what is right...
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It sounds to me like he got the wrong needle jets. If he was concerned, he should have checked/verified before he installed.
He will need to install the correct needle jets and appropriate needles for the bike to run correctly, IMHO.
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Yes double check the needle jets... they may just appear smaller when they aren't worn... it's hard enough to get the b4 to run well with the right parts.
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thanks guys for the input. here's what i've learned: my bike is a CA model with a CA specific carb. suzuki doesn't supply the CA model needle jets any longer, but only the jets for the non-CA US model. the part number is different, but both jets are listed as "0-9". so i'm not sure what the difference is. i called the suzuki dealer to ask if the non-CA jets would cause a problem in a CA model carb, and the guy basically said "no-comment." but the bike is running lean, so my mechanic thinks that having the non-ca jets could only be a good thing, because with the CA jets it would run leaner. i wonder what the difference is between the two parts, i.e. if they have different part numbers and yet they both are size "0-9." maybe the problem now has nothing to do with the needle jets, but with the slightly modified airbox or the aftermarket exhaust. i was just hoping to reduce variables.
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Find a dyno
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finally the bike's running well! whether or not the needle jets are the stock ones, the aftermarket clips (factory pro, i think) that the prev owner provided were the solution. i spent yesterday riding around on it and it is great. i was starting to get anxious because it was at the shop for a really long time, but in the end things seem to have worked out. thanks to everyone who gave me suggestions on here.
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:congrats: :motorsmile:
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Good stuff. Nothing better then riding your bike when its running well.