Help with Dynojet kit, Bandit GSF1200

[Bandit1200inFL]

I purchased a 2002 bandit 1200 with 14,000 miles.

[LowRyter]

I know years ago that Dyna jet kits had a pretty poor reputation.  So far as jet kits, Factory, Holeshot, and Ivan's have good reputations.  Now, I am not saying that Dyna Jets haven't been improved but 10 years ago when these bikes were new, that was the general tone.

I have a Gen 1 bike with the home made kit, with extra hole on the air box.  Don't have much to share on Gen 2 bikes.

Please take my opinion regarding jet kits with a grain of salt.  I am just relating general thinking that is years' old.

[rider123]

Well if its a dynojet, you'll probably need dynojet mainjets, stock ones won't work as the emulsion tubes are usually changed with the jets. Did you get the unused jets in the kit?(ie, 96, 100) Are you sure it's rich? "Breaking up"(incomplete burn I'm assuming) when hitting hard on the throttle usually means it's starving for fuel. If you hit hard on the throttle and it sort of loses power and sounds kind of wallowy and "wet" then it's usually rich. Lean will sound more "tinny" and a higher pitch. What notch are your needles set to?

 A good way to find out is take it on a long highway ride with higher rpms then pull the plugs when cool. It may just need a notch up or down on the needles if they are adjustable. I had my bike do something similar with over half throttle inputs and I just added a shim to the needle(made it richer at mid-range) and it fixed it.

For fun if you want to change the needles so that they are richer or leaner do this

Bad ASCII diagram
      __                  <----TOP OF NEEDLE
      I  I        
      I_I                                                                              
      I_I
 __ I_I__                <------------ C-clip (in middle position
      I_I
      I_I       <------ The little dashes are notches cut into the needle where the C-clip sits
      I  I
      I  I
      I  I
      I  I
      I  I
      I  I
      I  I
      I  I
      I  I
       V


Move the C-clip down a notch or two to richen up mid-range and larger throttle inputs

Move the C-clip up a notch or two to lean up mid-range and larget throttle inputs.

Take a look at the plugs if the centre white electrode has smudges of dark carbon you're probably too rich in the mid range/wide open throttle inputs. If its bone white, you're probably too lean at larger throttle inputs.

Also look at the base ring, which is the ring around the base of the plug where the ground strap is welded to. If you see dark sooty deposits you're mixture screws are probably a bit rich, if there is no or very light deposits that don't go all the way around the base ring it probably is a little lean you can turn out the mixture screws an 1/8th of a time to richen the low throttle idle mixture or turn in the mixture screws an 1/8 of a turn at a time to lean the mixture screws. Since you already said that it idles very nicely I wouldn't touch them for now since your problem is mostly with the larger throttle inputs I would start with adjusting the needles. Even if the main jets are off a bit adjusting the needle will help considerably.

WARNING: When you take the carb caps off, because you have a G2 Bandit, put a rag in front of the carbs as there is a little O-Ring that can get lost easily. Take the cap off CAREFULLY.

Is there an extra hole cut into the airbox or is it stock? If you want to see quickly without adjusting anything, whether it's rich or lean you could take out the rubber snorkle at the rear of the airbox(you can pop it back in later) which will allow more air to flow into the engine. If you are too rich you should notice an immediate increase in power. The problem with the G2(2001-2005) bandit's airbox is it designed for the 600 so it's constantly starved for air. While the K&N helps a bit it's still restricted by the dinky air intake, no amount of high flow filter can fix that.

For example I bought a hole shot kit in which you install larger jets but also cut an additional 1.5" hole in the lid to double the amount of air going in there. If you install larger jets without adding to requisite amount of airflow you just make it horribly rich, even with a high flow exhaust and filter it's still not enough. Removing the snorkle temporarily will turn the 1.5" hole with a 2" hole thereby increasing the total amount of air going into the airbox. It may not be a permanant solution but at least you'll be able to figure out if you need more air in there.


If I were you, for fun I would remove the snorkle(you may lose some low end torque) since it requires the least amount of work and see if you suddenly get some more power and it starts running better. If the hesitation is worse, then you are too lean at larger throttle inputs.

 It may not be a permanent solution but at least you'll know the deal of what's going on. Can you post a pic of one of your spark plugs?

[rider123]

What do you mean the needles are "high". Do you mean the needles have the C-clip toward the top of the needle?(leaner) Maybe moving the C-clip on the needles down one notch(richer) may help, you could always change it back.

And to be honest, the mechanic is right, having a jet kit in there should be better than stock as these bikes are neutered so much from the factory. The problem is that the Dynojet kits for the Second Generation Bandits(G2's) are notoriously finicky to get right where as the Holeshot and Ivan's are basically plug and play. That doesn't mean they are bad they just take a little more time tuning.

Also how do you know for sure that it's rich? When you rev it while parked on the centre stand do you see a puff of black smoke?(rich). Spark plugs sooty? Also if you are really rich and you rev it the idle will go BELOW the set idle then recover(at least the pilot screws may be rich). If you rev it and the idle goes slightly ABOVE set idle then settles back you might be too lean. Also if you are lean you will hear popping on deceleration. Do you have popping when decelerating?

[rider123]

Well if these conversion charts are right you may be really lean:

http://roadstarclinic.com/content/view/61/96/

Keihin* Dynojet* Mikuni
92 92 85
95 94 87.5
98 96 90
100 98 92.5  <-----This is you a 98 dynojet jet is only a 92.5 mikuni main jet(stock is 100)
102 100 -
105 102 95
108 104 97.5
110 106 100
112 108 -
115 110 102.5
118 112 105
120 114 107.5
122 116 -
125 118 110
130 122 115
132 124 -
135 126 117.5
138 128 120
140 130 122.5
142 132 -
145 134 125
148 136 127.5
150 138 130
152 140 -
155 142 132.5
158 144 135
160 146 137.5
162 148 -
165 150 140
168 152 142.5
170 154 145
172 156 -
175 158 147.5
178 160 150
180 162 152.5
182 164 -
185 166 155
188 168 157.5
190 170 160
192 172 -
195 174 162.5
198 176 165
200 178 167.5
202 180 -
205 182 170
208 184 172.5
210 186 175
212 188 -
215 190 177.5
218 192 180
220 194 182.5
222 196 -
225 198 185
228 200 187.5

These are what I found online. Going by this chart you have the jets BELOW what the stock jet would be. However Dynojets mark there jets by the size, IE 100 would be 1.00mm and Mikuni goes by flow, so a 100 mikuni jet(stock for the bandit) flows 100 cc per min. If you have jets in there UNDER 100 you're not even up to the stock jetting of the bike which would make it theoretically super lean, hence the hesitation. Now remember the Dynojet kits come with there own needles, slide springs and emulsion tubes, so maybe they have a more agresive taper, Wider jet bellmouth etc. Also the airbox is stock(no extra holes). I looked it up and he seems to have the right kit in there at least.

Here are the dynojet kit part numbers:

Bandit 1200 (2001-2004) 3151

Instalation insctructions:
http://www.dynojet.com/pdf/3151.pdf


After reading the instructions, boy it's definatly different than stock, for example the float height needs to be adjusted to 11-11.5mm thats a full 2mm lower than stock. Wow thats rich.(makes up for the leaner main jet I guess) According to the instructions the clip should be in the 4th notch from the top and the mixture screws should be 3.5 turns out from full in. It also says to use the 96 jet not the 98 but you just may need a bit more juice or they changed their jet kits and upped the jet sizes one up.

[rider123]

Well if 96 is for a completely stock bike maybe 98 is not enough. Looking at number 4 plug (number one still hasn't cleaned up from the previous leaks.) I'd say you lean at mid range and wide open throttle and a little rich down low. You can see your porcelin is very very white but the tip of the centre electrode and ring around the bottom is pretty black which mean your pilots are a little rich but as the rpm climbs your lean. If it was me I'd richen up the mid-range with a step down toward the needle tip on the C-clip and maybe turn the mixture screws in a 1/4 turn. However for now just leave the mixture screws where they are and concentrate on the midrange for now.

It may be the problem isn't helped by the K&N filter. For your generation Bandit it's wonky as hell to get dialed in correctly. I tried myself to get it tuned with a K&N and it worked(sort of) but there were holes all over the RPM range especially mid-range. Do you have the stock filter still? Maybe pop it in then go for a ride and see if that helps.

Unfortunatly you got the wonkiest filter with the wonkiest Jet kit you could get, but it's not impossible to fix.

Can you give me a pic of number 2 spark plug I believe you said 1 and 3 were leaking so they'll take some kms to clean up but 2 and 4 should be ok to look at. Also can you look down into the spark plug right at the bottom of the porcelin, this tells you general jetting, it should be light to chocolate brown/grey if its white then you know you're lean. Maybe take a picture with a flashlight shining into the plug so I could look, but judging by the porcelin I'd say your super lean in the mid-range and up top which would explain the crazy hesitation. Try the stock filter and see if that helps.

Installing a jet kit generally improves everything there are no compromises unless your a bracket racer or something and tune for all topend. My jet kit install has improved everything, acceleration smoothness is all improved over stock. My guess is you don't have enough jet and he's trying to compensate by the mixture screws because that base ring and electrode tip is pretty black(hard to see need more light). You may want to get new plugs soon as well it looks like number 4 is wearing a bit. Also new plugs will give you a better idea of whats going on since they will have fresh deposits.

Bottom line is your going to need more jet if you want to use the K&N filter it might even need more than the largest in the kit (100). I would pop in the stock filter for fun and see if it improves the bike. Unfortunately stuff that will work on 99% of the bikes out there doesn't on this bike which may explain that your mechanic thought it would work at the base settings. My guess is due to the EPA restrictions the bike is way underjetted from the factory to try a squeek by the requlations and in order to do that they have to jet the bike kinda wonky with a piddly air intake, etc. So just doing what's normal doesn't work. Hell my old 84 GS750EF had a larger air intake which was the days before all this EPA bullshit. Opening up the breathing just a little upsets the razor thin balance Suzuki had to overcome just to get the thing out the door. Frankly I'm suprised they did it. That's why it's better to buy a kit from either Holeshot or Ivan's as they've been tested already.


For example I have an additional 1.5" hole in my airbox and my mainjets are 110's thats like 4 sizes up from stock but really that how the bike should have come stock out of the factory. Even 2 1.5" holes your only using a little over half of what those 4 carbs can theoretically pull. Really according to Fastlarry's site you should have 2 2" holes which will give you 96% of what the carbs can pull but that would require even higher jets. I think a stage 2 kit which are the K&N pods the main jets are probably around 130 or so which is even larger. The dynojet kits uses mains that are SMALLER than stock so of course it will probably be on the lean side up top without some tuning and probably in other bikes it works fine because they aren't so hobbled out the factory so the stock jetting is probably closer to normal than this bike hence the dynojet kits work better on other bikes.

If I had your bike, it looks like the kit he installed doesn't have emulsion tubes so you could probably buy mikuni jets if you have to, I would try moving the C-clip down on the needle a notch or two to start off with and see if that fixes it or at least improves it. If not, you could try the largest jet in the kit(100), and/or go to the stock filter which doesn't flow as well at high rpm but it may help until you have your bike dialed right.

If the largest jet in the kit doesn't work you may have to go to mukuni jets or larger Dynojet jets(all the jets are cheap so don't fret it)If you are choosing Mikuni and are using the stock filter, my friend got very good results on his bandit with 102.5's a stock filter and a yosh slip on with a couple of shims on the needles and a closed(stock) airbox. Maybe for you it might be prudent to still use the nice adjustable needles from Dynojet. If you wanted to use the K&N you might want to use 105 or 107.5's if you are using Mikuni. You can also order the Dynojet jets from dynojet at 2 bucks a piece if you want to stick with that which may be a better idea since you already have the needles, float height and everything set up for dynojet.

If you want a super quick way of determining if your lean in the mid-range and up top just tape over a little bit of the snorkle hole with masking tape. No more than an 1/8th of the intake and see if it helps. I wouldn't ride around like that for a super longtime because the rich pilot settings will become even richer but you can try it for an hour or two and see if it works. Just ride around for 15 mins till the bike is warmed up then tape the hole a little bit(not the whole thing lol) and try hitting the throttle hard in the mid range. If it hesitates less then you know you need more needle and/or more jet.

[rider123]

Here are your options to test what you need from the highest and easiest fix/test to the most work intensive. You could also try these simple steps as you may be able to fix the bike without having it out of action with the mechanic on Monday.


1. Tape up a little bit of the air intake. Time 3 minutes max. All you do is remove the document tray(2 philips screws) and temporarily tape over a bit of the hole no more than 1/8th max and see if it help the hesitation. Note you should only be concerned with the mid-range as taping up the hole may upset the balance a bit down low. Ignore any low end richness. If it helps take the tape off and go to step 2.

2. Adjust the needles Time 20 minutes max. Move the C-clip on the needles towards the tip(down or richer) one notch at a time and see if that helps the mid-range hole(it will if you are lean there which is my guess) You need to take off the tank to get to the needles. Remember to put a rag or something in front of the carb caps as there is a tiny O-ring that can get lost easily. If it helps but not entirely fixes the problem after running out of notches(the lowest) put the needles back to stock(4 from the top) go to step 3.

3. Install the next larger jets (100) Time 2 hours max. I changed my jets a few times already and if you loosen the throttle and choke cables you can move the carbs enough without resorting to taking the entire carb set off the bike. If you are unsure let the mechanic do this. You may need to go back to step 2 to adjust the reason we put the needles back to stock after you've detirmined you need more jet is to start out as base settings as the larger jet may be too rich in the mid-range if you've kept the needle at the richest setting from step 2.


If you want to clean up the plugs a bit go for a long highway ride which should burn off the carbon built up from the initial leaks which will make reading the plugs alot easier.

[rider123]

Thats a good idea and the easiest. What I would do is tape the hole a little bit then go for an hour on the highway then immediately come back home let the engine cool and then post pics of the plugs. It's alot easier that way. Also I would try the larger dynojet jet first before switching to Mikuni(last resort). If you can do the initial diagnostic work  it will be alot easier to get fixed properly on Monday. If the plugs are new like you said then there may be something weird going on because #1 is way too rich(could be pilot screw settings) in the mid-range and #4 is too lean. Thats why it's good to go for a long run on the highway at a constant speed to clean up whats there so you can look properly. It could be that some of the cylinders are too rich and some are too lean. It's kind of rare but it does happen which will make the bike jerky at the point of where the mixtures are different. Did the mechanic sync the carbs? If you can take the pictures outside which has more ambient light.

As far as anti-seize paste or whatever I'm not sure what he means. I've never had anti-seize paste on the threads and never had a problem in the 25 years of owning bikes. Is he saying that some of the paste was leaking into the cylinders?

[rider123]

Don't give him advice just tell him the symptoms. IE, "well I taped up a little bit of the air intake and the problem got better", etc

[rider123]

Well if your jet is too small I wouldn't go totally crazy with higher rpm until you get it fixed. The reason why is you can actually burn a hole in the piston with it super lean up top like that. It makes sense though that your just running out of steam in the higher RPM with way too small a jet. In fact one jet size up may not even be enough. At least the jets are cheap from Dynojet($2 a piece x 4). Also you'll know at least you need more jet because if it improves then you're moving in the right direction.

To give you an example I'm 4 sizes up from stock with mukuni jets stock is 100 I'm at 110. If the bike is so lean up top it can't even reach top rpm wow is that lean! In fact I've never heard of a bike so lean in the top end it couldn't even reach top rpm. Considering your equivalent mikuni jet is a few sizes LEANER than stock I can understand why your having problems. According to the conversion chart stock jets for mikuni(100) are 106 for Dynojet. 100 Dynojet just may not be enough but at least you'll notice an improvement. I would keep everything Dynojet, ie springs, needles etc. And just try to up the mains. It's good to see your making progress though.

The reason the bike is slower with the stock springs is they are probably stiffer so the slides pull up less(leaner) with throttle inputs. Since you are already lean it just would make it worse. I think you're on the right track so even if you need bigger mains than the 100 I would stick with all Dynojet including any main upgrades. You may end up around 104 or larger Dynojet mainjets in the end. Actually you're doing us all a huge favour because up until now while we knew the Dynojet kits were a little tough to tune, now we definitively know why. In fact if you get the bike running great with Dynojet you can share the info for people who buy their kits without realizing that they need larger mains then whats in the kit.

After perusing the instructions again it seems to me that the Dynojet kit is really designed for a stock bike or with or without an aftermarket slip on and stock filter. Or alternatively a high flow filter and a stock exhaust. You have both. I just can't see having a smaller jet than stock even with fancy needles, springs, etc being enough for a High flow filter and a slip on. I'm sure if someone put the kit in there with a totally stock bike it probably would run just perfectly but then what's the point? Stock jetting while being still a little lean works perfectly fine. I guess it would make it better but if you're going to the trouble of popping in a jet kit you might as well get the full benefit by doing the other upgrades.

Just for a lark try throwing the stock filter(less airflow = richer) in there for fun and see if it improves the top end a little.


Here's a quote from the installation instructions which is ambivalent at best:

For mildly tuned machines using the stock airbox,
with stock or K&N filter. May also be used
with a good aftermarket exhaust system
K&N filter # N/A

No K&N  fliter part #(6001 btw)  and "May be used" kind of vague. Seems to imply you use either the kit with a K&N or stock filter and the stock exhaust or a good exhaust and stock filter. The little dyno chart they give you is within the realm of a stage 1 kit around 112 horsepower but I don't get the impression it was researched well as they don't have a K&N part number which kind of says to me they never used one to test it. Dales(Holeshots) instructions are huge and you can call him up if you have a problem. Seems like this kit was only ever tested with a stock filter which is my guess. But thats fine since you already know that you need bigger mains, in fact you don't have to buy a jet kit at all theoretically. You can always just buy a selection of jets and do it yourself, the bonus of the jet kit is the experimentation has been done for you. My friend who owns a bike shop just made one up himself with 102.5's a closed airbox a couple of shims and a Yoshimura slip on and stock filter and it worked great so don't get discouraged. You are definitely on the right track. There are many ways to skin a cat and all the engine cares about is getting the right amount of fuel. It doesn't care how or with what kit etc.

[rider123]

Oh and if you want to keep the lower toothed sproket you can get a speed healer at:

http://www.healtech-electronics.com/

But thats more money. To be honest for this bike while the gearing is a little tall I don't really see any reason to change the stock sproket size unless you do alot of in town or are maybe a drag racer or something but hey if you like it stick with it. Note your odometer will click off faster so you will have an artificially high milage count which may hurt resale value if you don't use the speed healer. Ie it'll say 50,000 kms when you've only done 45,000 kms, etc. Also your top speed will suffer a little as well. I think this bike tops out around 150 miles an hour or so so yours maybe "only" 135 or 140? Still in bad trouble fast if you get caught. Jetting should be number 1 priority, if you make alot of changes all at once it gets harder to pin down problems. Although with a lower toothed sproket, once the jetting is good you're going to be able to open your own wheelie school!

Here are the installation instructions. Looks pretty easy.

http://www.speedohealer.com/your_pics/gsf1200s/tutorial.htm

[rider123]

I don't know if this helps but it seems this gentleman is using the 100 Dynojet main in basically the same setup as you with good results. I PM'd him and see if he can pipe up what he did since he has the same kit.

http://forums.banditalley.net/index.php?topic=6864.0

[rider123]

If you look at the dyno run in that post, there is a little dip at mid-range that might be fixed up with another notch down(richer) on the needle. Also if you look at the Fuel/Air ratio in the lower RPM range <4000 he is almost dangerously lean and was complaining that it was a bit cold blooded. In that case turning out the mixture screws maybe a 1/4 turn would help as mixture screws control idle and part throttle/lower RPM operation. So thats why getting a Dyno is a good way of determining where you need to go.

For instance turning out the mixture screws does add a little to the overall mixture so since that is the most pressing problem I would turn out the mixture screws a 1/4 turn and I would bet that dip at the mid-range might be cured or much better, as going a full notch richer may be too much to fix that little dip since the fueling seems pretty good.

Alternatively you could try just the notch richer on the needle which will put more fuel in there sooner and that may help with the low end leaness. Really down low should be a bit lean as that is cruise so you want as much fuel economy when cruising but when you hit the throttle you want as much power. Also usually it seems the best practice is to tune down.. MAINJETS--->NEEDLES---->PILOTS

Towards the end of the thread he mentions he went to a full stage 2 holeshot solution and mentions he went from 100's to 147.5. I can only assume the 100's he mentions are the Dynojet one as that what comes in the kit. If you can get to what hes got with the 100's then just tweak from there you should be totally fine and you'll get around 112-113 horsepower instead of his 110. Trust me, you could really use that extra power when the liqour store is about to close!

[rider123]

Awsome! Glad it worked out for you, but drilling out the jets? Wow thats ghetto but I like it!

[rider123]

Well jets are not just a straight hole they are usually tapered like a bellmouth to ensure consistent and smooth fuel delivery. I figured instead of him ordering the real jets and waiting a week he just drilled it out and hoped you wouldn't care. Sure it works, but I'd rather have the real jets in there. If you want order a set. He said around 110 or 114?(pretty big difference) maybe order 108's and 106's if its too rich. It really doesn't take that much to pop new jets in. You might as well just do it yourself, you'll take your time and do it right. Start with the richer (108) and work down(if necessary), that way it's safer in case 108 is too lean.

As far as fuel injection is concerned it is more effecient however on light loads it can get snatchy, especially on small vehicles like motorcycles. Also to tune it you need a $350 Power Commander or other programmable EFI module so for that amount of money you could have 20 sets of jets and a slip on high flow exhaust. I'll take the $8 or $16 set of jets. I know carbs are going the way of the dodo but they do have some advantages over fuel injection.