Carb troubles-Wet Diaphragms?

[rmack87]

Howdy folks.  Long time reader, first post.  Me and two buddies bought three bandit400s last christmas...we have been riding them in the highlands of lesotho.  slowly some issues have started to develop with one of them...developing in the following order:

1.  Hard starting when hot.  Starts easily cold.  Either starter will crank slowly, as if combating crazy pressures in cylinder, or it will crank rapidly....pitpitpitpitpitpitpit...but not turn over unless bump started.
2.  Loss of top-end power.
3.  Overheating in high-stress situations(up the mountain).

Cleaned the carbs a number of times now.  Doing some reading here(you guys are awesome) i learned that these(with the partial exception of the overheating) are all signs of running too rich.  Throw in the high alititude and things were making sense...I reset the float heights, and have even turned the pilot screws out to just .75 turns.  The bike is running better, but not quite as well as the other two bikes.

One interesting thing that I dismissed early on was a kind of grimey, sandy sludge on the slide valves of the carbs the first time i cleaned them(like a smoother, more putty-like, less abrasive version of grinding paste).  I wiped it off and didn't think too much about it.  Thing is, i recently discovered this grime will re-appear even after just one 300k ride.  Also my diaphragms are always somewhat wet, making me suspicious that petrol is spitting back up to the diaphragms/slides, degrading them, and the sandy paste i'm observing is actually the plastic of the slides having been eroded and ground by the petrol/grinding against the carb assembly.  I looked online to see if it's normal for the diaphragms to be wet but can't find any answers.

Are wet diaphragms normal?  Where is this sludge on the slides coming from?  Thanks a ton in advance!  Cheers!

-Ryan

[rmack87]

sorry, i also should have mentioned...the 'wetness' is oily...not like engine oil, but like engine oil and petrol have combined and given me this thin, non evaporitive liquid.

[pmackie]

How do the plugs look? Any smoke out the exhaust? Have you checked the valve adjustment?

I think I would want to do a compression check.

[rmack87]

Plugs are all rich-ish looking...not fouled, but definitely not the happy tan color i hear so much about.(still have yet to see one with my own eyes!)

yup.  Smoke is there, but only when the bike is cold.  It's a black smoke that I suspect is from running too rich.  The other bikes do the same thing.

I bought a compression tester a while back and it wouldn't fit the bike.  Tried welding an old spark thread to the adapter and just made a mess...was able to rig up a pen glued into an old spark sleeve gasket that fit pretty snugly, and tested the compression by 'feel'.  All cylinders 'feel' strong but of course i realize that doesn't inspire too much confidence.(working out of a small village in the mountains in lesotho...can hardly work with the tools we'd like to)

So...to Valve clearances...glad you mentioned that!  I was so locked into the carbs that I wasn't thinking about this.  We adjusted the valves shortly after we started having problems, and when double(and triple...and quadruple...) checking the heights after we set them we almost always figured out that something had changed!  We were following the manual's procedure at first....but then later decided the heights were most consistent when measuring at 180 degrees to the cam's "elbow".  Was too dumb to realize it then but now i'm thinking...maybe the cams are worn, giving us different clearances at different rotations(we were always measuring away from the elbow of course).

Which would mean that the measurements are so close...when the metal is cold the valves are happy...but hot and expanded the behavior changes drastically!  Makes sense with regards to the symptoms of the bike!

So now my next experiment i think will be to over-set the valve clearances.  What are the limits for this?  How much should I go over from the manual's specs(for intake i think .15 and exhaust .2mm)

[rider123]

Improper valve clearances wouldn't really have that much effect on how rich the bike is running. Just a few questions to help us to help you out:


Year/Model of bike and CC
Main and Pilot jet size
Turns out on the mixture screws
Jetted, stock?
Aftermarket pipe?
Float height on carbs?
Emulsion tubes worn in the carbs(could be it as it would dump alot of extra fuel on the slides)
Needle position or shims? (A really rich needle will also dump fuel unnecessarily)

If you don't know all the info just try and do the best you can. A big hint would be if the bike has been Jetted with an aftermarket pipe. Perhaps the previous owned did a really crappy job jetting it(we see this alot) and now it's super rich. Usually when there is alot of fuel dumping into the slides it can be these things:

1. Mainjet way too rich
2. Mainjets actually worked themselves loose and it's just a big ass hole with the emulsion tube the only thing holding the fuel back(saw this once but usually only one carb will be bad not all of them)
3. Needle extremly rich will also dump fuel
4. Float height set too low which will flood the carbs
5. Pilots way too rich or mixture screws turn out too many turns will make the low end rich
6. Pilots working themselves loose
7. Emulsion tube is ovaled and worn dumping extra fuel in there when the slide comes up(can be sort of temporarily fixed sort of by lowering the needle a notch or two)
8. Air filter dirty and clogged
9. Emulsion tubes loose or O-rings dead

The best advice I can give you is take one of the outside floatbowls off so you don't have to pull the entire carb bank off and take a look in there. Unscrew CAREFULLY the mainjet and pilot jets and write down the size. They should be marked with a number, mainjet sizes for a Bandit 1200 will be like 100, 110, etc in steps of 2.5. Pilot jet sizes would be around the 15, 17.5, etc. Dynojet mainjet sizes will be in steps of 2. Mikuni jets are in steps of 2.5.

If you have a Dynojet kit in there, they use crazy ass rich float height settings to achieve their jetting but their Mainjets are smaller. If you have a Bandit 1200 the Dynojet kits suck for some reason on this bike. Since the Dynojet mainjets are actually smaller than stock sometimes people after maxing out on the Dynojet kits will order Mikuni jets instead which really make it rich, it just turns the jetting into a cluster phuck. Anyway don't sweat it even if it's all messed up depending on the model we can suggest the proper jets to try and sort it all out.

For example I have a Generation 2 2005 Bandit 1200 with a Holeshot jet kit installed:

Mainjet: 112.5
Pilotjet: 15
Mixture screws 3.75 turns out from lightly seated
Float height: 13mm
1.5" extra hole in the top airbox lid
Stock filter
5 shims on the needle(or if you have an adjustable tell us how many notches from top)
Muzzy Slip on with mid-pipe


If you get this sort of info it would really be helpfull. For example one guy had some winner install a jetkit on a Stock exhaust and intake.(WTF?) Needless to say it was rich as hell, you can't just add fuel or air without adjusting either to keep an apropriate ratio. See what you can come up with and we can help you more. Just be REALLY CAREFULL with those jets, they are soft brass so don't go jihad screwing them in and out, nice and snug is fine.

If you have the pilots out only 3/4 of a turn you either are compensating for a super rich mainjet as you said the top end is crappy or the emulsion tube has ovaled and is dumping extra fuel in there. Or your float height is crazy low or your pilots have been changed out for super rich ones. Did you take a look at the emulsion tube to see if the brass is worn? The emulsion tube is the hex nut tube that the mainjet screws into. You want to check to see if the top of the emulsion tube where the needle seats is perfectly round and not ovaled. Here is a pic of an ovaled emulsion tube needle seat:


Is it all the carbs that are rich? Which would suggest the settings are off. Do you have a stock or a K&N filter? If it's a stock filter the bike would run alot better with a K&N if it really was that rich, however the real solution is to jet it to what your normal setup is.

From just your symptoms with zero information I would guess the mainjet is way too rich. Once you have the mainjet sizes, etc we'll be able to help you more. These bikes are almost stupidly easy to tune so if the previous owner phucked it up don't worry about it, we can probably get you set up quickly. Black smoke and running better when cold than hot is a sure sign of richness. Valves only affect the size of the fuel/air charge not the ratio of fuel to air as the wet slides will attest to is way too rich. Is your needle adjustable? If so lean it out one notch for fun by moving the C-clip UP one notch and see if you suddenly get some more power when warmed up.

[rmack87]

Awesome, thanks rider!  

bike is a '93-ish import(i suspect from japan) that i bought in south africa, reg papers say '93 and that service manual seems to be accurate so far, with the exception of some small electrical differences.

Before i dive into the carb details, all three of our bikes run rich, likely as a consequence of altitude.  All of them have black, smokey exhaust cans but they are not drinking oil(well one of them is, but not much...and for old bikes i can't complain).  They all improve when we go down to the lowlands, and i suspect they'll be great at sea level(which we are hoping to take them to the coast  very  soon).  This bike, while running rich, isn't running INSANELY rich.  It never fouls itself out.  Even at the top end, i'll sit there with the throttle wide open and get nothing more...it doesn't sputter like it's fouled...it just stops giving like the slides aren't rising the needles out or something else is going wrong...it's not flooding itself out, really...so while the starting problem can be tied down to running too rich, I think something else is happening with regards to the top end.

Pmackie's noting of valve clearance sounds promising, actually...if a clearance is set too close, the bike valves are sealing up nicely when the bike is cold...then when the bike gets hot things expand and the valve doesn't seal...in the case of the intake valve maybe during compression the mixture shoots back into the carb, cutting into performance, causing overheating, soaked diaphragms, and MOST telling/promising is the erratic starting(when hot it never starts via electric...either super slow cranking or super-fast cranking...but never normal).  The way it starts makes me think...sometimes the valves are sealed and the starter is struggling with the hot engine...turning slowly.  Other times  when it's hot enough maybe there IS a valve leak(or two) and the starter turns the engine super-quick but with the loss of compression still can't start the bike.

That being said, keeping things simple it makes plenty of sense just to say it is just flooding when it's hot, so i really want to get all the carb info to you ASAP.  It will be a few days.  Right now i can say:

Carbs:  Twenty year-old bike, and the needles and jets look relatively new.  Either it's been rejetted or parts have been replaced.  Can't remember for sure all of the specs, but by my memory all of the jets were in the 90's size-wise.  The butterfly valves have a 95 stamped on them.  At one point i had the suspicion that the main jet needle was too long, as it extends a good centimeter into the emulsion tube with the slides raised completely.  Is that normal?  Needle clip is currently set at the highest position(leanest), and i'm suspicious that by actually lowering the clip(making it run more rich), the needle will come out of the emulsion tube more and give me the top end back.  Is that possible?  Float heights i'm certain are good at 14.6 plus or minus a little(i used the 45 degree angle trick to help make sure the little springs on the needles weren't compressed).  Carbs have also recently been balanced by a professional.  It did a lot to help the idle.  He thought he had cured the bike but never got it hot enough i suppose and never saw the whacky behavior.

In the mean time, while we wait for my lazy ass to dig up the actual jet sizes:

1.  Does my asessment of the valve clearance, esp. With regards to the starting, make sense?  Is there an explanation for why running rich would make the engine turn over quickly and not catch?(trying to see if maybe i'm barking up the wrong tree with carbs).

2.  If the main needle is too long, will it cut off the top end of the throttle?  Will setting it a clip down(making it more rich, which i really don't want to do) restore some top end?

3.  If I do decide to dig in and re-set valve clearance(which i don't think could be a bad idea), what is the maximum clearance i can give the valves, to help account for cam wear?

Thanks everyone!  Cheers!

EDIT:  forgot to mention, something that might make you all cringe a little is that the air filters are all stock, and warped to hell.  I've tried duct-taping the holes with no noticeable difference in performance.  The 'filter' is literally just a spongy black foam that sits in the air box.  Currently, the bike with the problems has the nicest of the air boxes, actually.  It's probably doing its job pretty decently.(better than the other two bikes which aren't having troubles).

[rider123]

I'm assuming by your jet sizes etc, Your talking about a Bandit 250 or 400 or correct? Don't worry about the needles extending into the emulsion too far thats normal. Since you're lucky enough to have adjustable needles you don't have to worry, even with it on the lowest(richest) setting it's not going to come out of the emulsion tube or anything. As you go up in altitude you have to reduce the mainjet size. The needle only affects the mid-range and 1/4 to 3/4 throttle inputs. Top end and over 3/4 throttle is all mainjet. If you want to see definitively what the top end is doing is find a place you can really hammer the throttle without going to jail get up to third gear and accelerate full throttle to near redline then hit the kill switch just before redline and coast to a stop. Be careful as the plugs will be hot but try and take one of the outside plugs out of there. The top 2/3 of the centre electrode should be burned clean and there should be a nice light to dark grey ring around the base where the ground strap is welded to and deep in the plug near the bottom of the electrode should be a light grey tinge to it. If the base ring is black or has sooty deposits on it you are too rich.

You can also use this to guage your cruise and needle settings as well.

For example to test to see if you are rich down low, ride around with light throttle inputs going through the gears gingerly and just sort of cruise around at less than 4000 rpm and pull the plugs. Same thing here your base ring should be a light to dark grey and there may be a little more deposits on the centre electrode and the tips of the electrodes closest to the ground strap should be a dark grey max. If you see sooty black tips with a sooty black base ring and some dark colouring on the tips of the ground strap than your cruise which is handled by your pilots are probably too rich. If you see some dark streaks on your centre electrodes is also a sign of the needle at cruise may be a bit rich as they all sort of overlap a bit, however since you have it on the leanest setting I kind of doubt it.

To test the mid-range its the same sort of deal but in the case you want to do a few passes with 1/2 throttle from say 4000 rpm to 7000 rpm or whatever the mid-range is based on your redline. So the best way to do this is cruise until 4000 rpm in 3rd or 4th gear then peg the throttle at 1/2 or so up to 7000 and go back down and do this a couple of times. You're basically artificially doing a few passes in the mid-range. At the last pass hit the kill switch at 7000 rpm and coast to a stop. Check the plugs, needle position with show up as streaks on the centre electrode as well a the base ring. Base ring should be a full turn of light to dark grey with either a clean centre electrode or some light to dark grey streaks on the centre electrode. If the base ring is sooty and black or there are black streaks on the centre electrode then the needle is too rich. In fact I would be worried since your needle is so lean(could be previous owner is compensating for a crazy ass rich mainjet) I would doubt that the mid-range would be rich, it may actually be very lean.

The best way to sort everything out is to give us a little more info:

For example pick one bike that is the least screwy so it will be easier to get running right then just do the same on the others. So on this bike:

Does it have an aftermarket exhaust or stock? An aftermarket exhaust will flow alot more than the stock and will need a richer mixture.
What CC's/Model is this bike? There are 2 types for example of the 250cc, one has Variable valves which may be the reason the valves are wacky, I don't know how the variable ones are adjusted but maybe there is a special procedure?
Try and get definitive jet sizes for Main AND pilot. Generally the needle should be on the centre or neutral position for testing. The fact that it's on the leanest which is extremely unusual leads me to believe its a jet job gone bad and the guy before you was compensatinig for a rich main or pilot jet. Which would make is screwy, ie rich down low and lean at mid, then rich up top for example.
Is the air filter stock or a K&N? Is the filter dirty? Has the K&N been cleaned and re-oiled properly? If you put too much oil on a K&N filter it will totally screw with the jetting(make it rich)

Try and give us the model and CC as there are Bandits from 250 to 1200 CC so we need the model so I can scare up the manual and look up what jets should or should not be in there. From the jet sizes at least you probably have Mikuni jets in there which helps alot for sorting it out. Since jets are only a few bucks each it's not super expensive to jet for your altitude.

If you want for fun to see if you get a little more omph put the needle down one notch richer and see if the transition area in the mid-range is stronger, ignore any other richness overlap for now. You can always set them back if it doesn't go well but that will give you an idea if the mid-range is artificially lean. Even if you are super rich, if the mid-range is improved then you definately know that there is some compensation going on there.

As far as the valves go, I had a similar problem with a GS750EF, what the problem was is the previous owner let it sit too long and some of the valve springs lost their strength so the bike wasn't sealing the cylinders properly when hot. If you do a leak down test when warm this will show up as lost compression or slow leaking compression. All I did was buy new springs, pop them in re-lap the valves and the bike drove like new. Since your bikes are 20 years old it's possible the valve springs are tired and when heated up are losing some strength(heat makes metal softer) and not sealing the valves properly. It's not that hard of a job to do, just be sure to buy enough beer as you don't want to run out mid way!

If you want to be lazy, just skip the lapping process, I did it in winter so I didn't care how long it took. Try replacing the valve springs on one of the bikes and see what happens it's not super expensive and after 20 years they are probably due anyway so it's not like your throwing money away.

Although on the flip side if the bike is super rich it will have problems starting when hot. For example on ANY bike if the bike is warm and you pull the choke to full it will be hell to get the thing to fire up if at all. It will literally be drowning the engine. When the engine is cold it needs the dump of fuel to get started until the engine is hot enough to use a lean enough mixture. A leakdown or compression test when warm will tell you one way or the other. Thats why I suggest fixing the least phucked up bike and use that as a benchmark for fixing the others. If you have one that is jetted correctly with a new air filter with properly sealing valves your gold just reproduce and fine tune the others and your set.


EDIT: If the air filters are warped and phucked up it may be worth it to go and buy OEM stock airfilters for all the bikes just so you can eliminate that possibility.(God knows when they were last changed) If the previous owner totally butchered the airboxes or whatever you may have to re-jet to use K&N pods just to sort out the insanity. At least you'll get some extra power. Do all the bikes have aftermarket exhausts? And what the hell are they?(model)  

Fill in the blanks:
I have a 1993 Bandit _______:

A. 250
B. 250 VVT
C. 400
D. 600
E. 1200
F. I have a Kawasaki you retard!

[rider123]

Opps forgot the starter. There was a guy here who had a wonky starter that when hot wouldn't have enough power to turn the engine over. When it doesn't turn over you say its making a grinding starter clutch slipping noise? or just chugging? I say we try fixing one thing at a time before we start tackling all the problems at once and problem number one is having non-valve seal-age and wonky jetting setups. I would do the cheap stuff first, go and buy OEM filters to replace the bent and warped ones for all the bikes that would probably help the richness immediately because God knows when those filters have been changed. Who knows maybe the guy never changed them and the bike is rich as hell because the filters are clogged.

Next choose the least wonky bike to get running right so you can use it as a bench mark for the others this will save time and energy down the road. Do those simple things first and it will be alot easier for you. If the bike you choose you feel the valves are weird it might be worth the money to get a compression test when the bike gets wonky and explain it to the mechanic so he can do a leak down/compression test.

[rmack87]

Super response.  Thanks so much for taking the time to make it clear.  

Sorry about the confusion the bikes are '93 bandit 400s.  I think the one with the issues is a japanese import.

Right now, for the other two bikes i'm of the opinion--if it aint broke, don't fix it--.  Each bike is quite unique with regards to mods, and carbs.  One of them is a vv(the one with problems is not), and each probably would require some unique changes with the carbs.

Truth is we will only be riding the bikes for a few more months, mostly down at sea level, and then ditching them in south africa to go back home to the U.S.  So it's not worth our time/money to invest 'too' much.  That being said, we want the bikes to run well and understand that there is no magic button to press to get things sorted out on this bike that's giving us problems.  In the end...the other two bikes are running well...not perfect, but well, and I'd rather not risk making anything worse.  If it aint broke, don't fix it, kind of thing.

As for special mods to this bike...nearly everything is perfectly factory with the exception of some wiring.  The exhaust can has a big-old ding(EDIT:  Huge-ass dent going along the whole length of the can) on the side facing the bike...like it was dropped and then rotated and re-set for aesthetic purposes.  How would this affect the tuning of the bike?

Went for a run today on it with the needles raised(clips dropped to be clear) one clip.  More grumbly and pingy through the exhaust on the whole range of revs but initially i thought it had more top end power...i think it was just that the bike stayed cooler for longer, though.  When i got to city it was nearly impossible to keep the bike alive at low revs as the flooding got bad.  Anyways...the leanest setting on the clip is where it will stay for now.

I'm suspecting main jet more and more the more you explain to me.  May have a chance to look at it soon.  How do you get that sucker out?

I like your idea of valve springs...is that a generic part or do I have to buy OEM?  Thing is these bikes are gray imports in South Africa, meaning Suzuki dealerships can't even order parts for them.  We also want to get going on a trip soon.   When cold, the springs SEEM very strong, but i don't know how much that behavior changes with heat.  Perhaps i can measure them and compare to manual spec?

Starter is not grinding...just sometimes trying to chug along but not getting it done, while at other times racing quickly.  I don't think the starter clutch is slipping or anything.  Also realized today that pulling the enrichening lever when it was turning quickly but not starting made it turn even more quickly...definitely thinking valves as a suspect on that end.

So...is allowing some extra valve clearance unadviseable??  I'd really like to try it, and then if that doesn't help invest in some springs.

Thanks so much for your help!  Currently on my list of things to do is A. Check main jets for wear and B. Give extra clearance on the valves.  Cheers!

[rider123]

Changing the mainjets is not as hard as it sounds. In fact if you loosen the throttle and choke cables usually you can tilt or slide it enough to get in there to change them out. Of course its easier when you take out the bank of carbs. Look for the mainjet that will be screwed into a long hexagonal bolt which is the emulsion tube. Here is a pic of my Bandit 1200 carbs which is slightly different but the general layout should be the similar:



As you can see the mainjet is screwed into the emulsion tube. The thing called the "Mid-Jet" is the starter circuit jet.

Here is a microfiche for a 93 Bandit 400 carb bank(American model anyway):

http://www.bikebandit.com/1993-suzuki-gsf400p-bandit/o/m6137#sch246848

Its kind of a crap picture but #30 in the microfiche is the mainjet which says 105 but I'll double check that with the downloadable manual in the downloads section. If you have a Mainjet that is LOWER than stock. It's quite possible someone popped in a Dynojet kit on a stock exhaust and mid-pipe which kind of defeats the whole purpose which would make the jetting wonky. The best info you can get is to take off the float bowl of one of the outside carbs and check what's in there for sure. When I get back from work I'll be able to look it up at least what should be in there stock.

[pmackie]

1.  Does my asessment of the valve clearance, esp. With regards to the starting, make sense?  Is there an explanation for why running rich would make the engine turn over quickly and not catch?(trying to see if maybe i'm barking up the wrong tree with carbs).

Hey Rmack87

123 has given you a lot of jetting info, so I'll stay away from that area.

It is NOT likely that that the valve clearances are allowing significantly more pressure when cold than when warm, but I am concerned that based on your description, that you may have two issues:
1. The bike sounds rich. This would cause it to run better when cold, and worse when hot.
2. I am concerned that 1 or more cylinders are low on compression. Once warmed up, the combination of low compression and the rich jetting causes a fall off in performance.

I thnk you should be doing a proper compression test, both dry and wet, and if at all possible, a leak down test.

Of couse, you should make sure that the valves are properly adjusted first. You CAN set the valves to the Loose end of the spec, but don't get too carried away.

[rider123]

I agree with PMackie a compression test would really give you an idea on how well the valves are sealing the cylinders. Even if the compression is fine(hopefully) at least it would eliminate that as a source of a problem. If you want to test the cylinders without taking the timing cover off to turn the crank you can put the bike on the centre stand and put it in top gear, then you can just rotate the back tire to turn the engine.

Another good test to see if the valves are sealing well is measure the compression at the top and hold it there. If you see the PSI's slowly die off like a leaking tire then you know that cylinder is not holding its compression and the valves are not sealing well. Some die off may occur just from ring leak or the compression guage not sealing in the sparkplug hole etc. but if it's going down fast then you know those valves could probably use some new springs and a lapping. It made my GS750EF run like new.

Test if possible cold then hot. We can work on the wonky jetting together as it will be easier than redoing all the valve springs etc. Like I said invest the $20 a piece and get new filters to replace the demented old ones. You never know it may completely fix the problem with the wonky jetting. I've seen some pretty rough airfilters in my time from laziness or lack of knowledge that they need to be changed out so a quick $20 is a good place to start before outlaying more money. A new filter may even fix the horrid richness who knows.

 Even if it's jetted crazily a set of 4 mainjets is like $12 so you don't have to spend a crazy amount of money to get them running well which translates into more cash for you when you sell them. The $12 invested in jets may turn into $200 come selling time.

I believe you said you had three bikes? Even if one needs alot of work just sell it with the pair as a parts bike and you don't have to spend a penny on it that why I said to concentrate on the least phucked up bikes first which will give you confidence to tackle the demented ones and the least amount of money as well. Once you get the jet sizes on the least demented bike we can start to tune it a little better than all you have to do is replicate the results with the other two.


You said that when you put the needle one notch richer you seemed to get a little more power until the bike fully warmed up which tells me that the needle is set way too lean and the reason it's so lean is to compensate for either a rich mainjet or a rich pilot jet. If I get the numbers I can compare against what is stock and we can see which is the problem area. It could be that some fool went up on the pilots to try to improve the cruise range instead of giving it just another notch richer on the needle or he read something on the internet and like the broken telephone game got it wrong. If the pilots are only .75 turns out I'd say something is definitely rich. I believe the Bandit 400 needs them about 1 1/2 to 2 1/2 turns out, if it only needs .75 to keep it from dying that could be your problem there.


I did find the stock jet sizes however for you(American model):

Mainjet: 100
Pilot jet: 32.5

Since you have stock exhausts on there any jets other than those the bikes have been screwed with. I've been sort of half assed searching around and I've seen jetting done with K&N pods with like the mainjet at the 127.5 range and the pilots as high as 37.5 so if the previous owner just gets these magical numbers in his head not realizing you need an aftermarket exhaust system with pods and pops those jets in......Since some of the bikes airboxes have also been butchered I'd say someone was screwing around.

[rider123]

Ok I got some more info for you. You can download a clymer guide for your bike here:

http://www.carlsalter.com/suzuki-service-manuals.asp

Chances are you have the Euro/Canadian/Asian model so you probably have the BST33 mm carbs not the American BST32's with the plugged up mixture screws and slightly neutered EPA jetting.

So to save you some time here are the stock settings(Anything other than the States):

Mainjet: 102.5
Pilotjet: 32.5
Mixture screws: 1 1/2 turns out from stock

Now for your bike there are two models the American and the rest of the world. It's possible some guy was reading something on the American model which needs more jet to come up to Euro/Canadian standards. If you are .75 turns out from stock I can almost guarantee you your pilots are at least one size up at 35. If not that the mainjet is larger than 102.5 so you need .75 turns out just to survive. The previous owner maybe read something on an American board to try and de-neuter the bike but is using settings for a slightly different carburetor. Who knows? Get those Jet numbers!  

[rmack87]

great.  Thanks guys.  How do I remove the needle seat to check for wear?

[rider123]

Well the microfiche sucks but there should be a hexagon stalk that the mainjet screws into. That is the emulsion tube just use a 8mm wrench and unscrew. Inspect the O-Ring as well that can be a source of leakage. However with the amount of fuel you have going in there I doubt its just an ovaled needle seat but it doesn't hurt to check.


EDIT: Just taking a side view of the CARB in the clymer manual it looks like the emulsion tubes are press fitted, if so then don't even bother checking the needle seat as you need to take the carb totally apart and tap out the emulsion tubes. Put it this way if you unscrew the mainjet and there is just a stalk there with no way to unscrew what the mainjet is screwed into then forget it. To be honest with the amount of fuel going in there I doubt a slightly ovaled needle seat would do that. What a ovaled needle seat does is just makes the mixture a little screwy(rich on the needle mostly) which can be fixed temporarily by leaning out the needle. IF your emulsion tubes are press fitted, basically non serviceable, you would litterally have to take the carbs entirely apart and get a punch to punch out the emulsion tube. Not worth it. If you still want to check you can take the tops off the carb and remove the slide and look down in the throat of the carb, you'll see the seat where the needle sits through the top of the carb, just have a quick check. Getting the Jet number is much more important. Just take an outside carb floatbowl off while the carbs are on the bike.

Considering your probably LEAN on the needle not rich, I would highly doubt the needle seat is the culprit, not with that much fuel in there.