Author Topic: Jetting Thread  (Read 87598 times)

Offline Banditmax

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Jetting Thread
« on: May 31, 2007, 09:17:32 AM »
As there are quite a few of us with non standard bikes out there i thought it'd be good to start a thread sayuing what engine mods you'd done and what jetting you are using. Please only posts with specs in start a new thread if you have problems with your jetting
 Heres Mine at the moment its running well no big flat spots and pulls real good at top end. But not completely happy with the fuel screw setting at the moment.

 Height above sea level: Around 750-1000 feet
 Outside Air temp: 14.1c
 Bike is: 1993 first gen non V model Japanese import. 33mm carbs.
 Engine Mods: In airbox K&N filter with standard lid. Waco full racing exhaust system with baffle installed. M-max derestrictor box. Carbs have just been fitted with all new o rings.
 Needle: Factory Pro ti needles on 3rd clip down
 Main: 97.5
 Pilot: 32.5
 Mixture screw: 1 and 1/4 turns out
 Float height 15mm

Edited thanks for the tips guys

Offline PitterB4

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Jetting Thread
« Reply #1 on: May 31, 2007, 09:56:12 AM »
Just a couple comments from your trusty Mod and I'll get out of the way of this thread (which is a great idea).  We actually started one of these a year or so ago but I don't think it got very far.

Knowing which B4 you have will be helpful (V model, first or second generation, US 32mm carbs or not...).

Also it would be interesting and useful to document your satisfaction with it.  E.g.: "Runs awesome up top but has bad flat spot at 4K"...

Go get 'em!
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Offline stormi

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Jetting Thread
« Reply #2 on: May 31, 2007, 03:04:27 PM »

Awesome timing guys!  We're going to have to jet Dita here right away, and I haven't a clue where to start ( and have been too busy to search the forums so far)

Dita - 91 Bandit 400 - SOLD
Blue - 02 Hornet 919 - Perfect Gentleman
02 KTM 200 EXC - Sold
08 VFR800 - Lowered 1.2"
17 KTM RC390
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Offline andrewsw

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Jetting Thread
« Reply #3 on: May 31, 2007, 03:15:27 PM »
altitude: 1500ft
average temperature year round ( a completely useless number): 47.3 F. summer temps avg: 65F, but that's 95F during the day and 50F at night... IOW, jetting is a pain.

Mods: K&N filter in stock airbox with no snorkle. Yosh full 4-2-1 exhaust,

Main: 105
Pilot: 32.5 (stock)
Needle: Factory Pro, position 3 (I think, gotta look)
Mixture: 3.25 (EDIT: woah was I wrong!! had listed 1.25..., 3.25 might be too much and may be a cause of some softness between 4-5k when very warmed up)
floats: 16mm, raise to try to cure softness at 5k or so (was15mm)

runs real good, but I think she might need more top end. I might try a 110 main, we'll see. I think there may be more unknown mods to this bike because of a couple clues: 1) I'm running more jet than a lot of folks (I think). 2) this bike has been drilled for safety wiring for the track, so I can't say whether anything has been done inside the case, but its certainly more likely than if she wasn't drilled.

MORE EDIT: I'm getting some softness between 4-5k. Shows up when very warmed up (after a long ride) or when very hot out. If cruising nicely at that engine speed in say 3rd gear (what is that, about 35mph?) and I crack the throttle just a bit (maybe 1/16th) it will stumble and miss. if I give it more, it clears up. I think its either too much on the mixture screw (though that should be mostly out of the picture by then) or maybe float level. Its not a big deal and if I don't try to ride so nicely, then its no problem  :motorsmile:

MORE MORE EDIT: a supposed factory trained suzuki mechanic claims that my softness is either the pilot jet or the float height. Float height is easy (since I only have stock pilots available at the moment). Will try 16mm just to see what it does. Also, am I rich on the fuel-air? it doesn't stumle on the throttle blip... but its still out pretty far and maybe that is affecting the 4-5k just off idle thing.

MORE MORE EDIT EDIT: I'm still fussing with a little bitty rich spot between 5-6k and its driving me crazy. I raised the floats, lowered the fuel level to 16mm and its better, but still a drag when its really hot. (we were pushing 95F today). It only shows when fully warmed up and I crack the throttle just the tiniest bit off cruise at 5-6k rpm. it goes away easily with a touch more throttle. Its annoying because when cruising in that range, there's always little tiny throttle adjustments and it sputters just a bit... ack. also tried turning idle screw in to 3.0 from 3.25... no go, starts to lean surge a bit and won't idle as smooth...

Offline BrianM

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Jetting Thread
« Reply #4 on: May 31, 2007, 03:49:43 PM »
For the time being (I'll edit when it changes, again)

5500' above sea level
32mm carbs (completely rebuilt, nothing skipped)
stock airbox, filter, exhaust
Main: 95 (and still too rich)
Pilot: 30
Mixture screws: 2.25 turns out
Float height is stock
Needles are stock and shimmed up 3mm

And I'm still running rich.  Odd to see so Little mixture when I've never had a bike use less than 2.5 turns before, but I'm also running the smallest pilot possible (made a HUGE improvement).  I'm planning on getting some Factory needles, and dropping another main.

     BrianM ~ 1991 Bandit 400

Offline Thief400

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Jetting Thread
« Reply #5 on: May 31, 2007, 11:08:27 PM »
Heres the setup for my 91 with 33mm carbs

660 feet above sea level
195 thermostat
yosh zyclone 4 into 2 into 1 pipe
air box with 2 extra holes and snorkle removed
degreed cams
timing advanced 2 degrees
127.5 main for spring temps up to 68 to 70F
125 main when it gets hotter out
needle in the stock location 3rd groove with this pipe
stock float height
stock pilots
air screw 2 turns out

Offline interfuse

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Jetting Thread
« Reply #6 on: June 21, 2007, 11:50:09 PM »
altitude: 76 m (249.3 ft)
temperature: -35 to +35 degrees celsius (right now its closer to 30) average is 9 degrees
MODs: Stock airbox, stock filter, yosh exhaust, factory jet kit, US model needle jets
Main: 95
Pilot: 32.5 (stock)
Needle: Factory Pro, middle clip
Mixture: 2.25
floats: 15mm

Verdict: Slightly lean between 4-5k and around 8k almost unnoticeable once hot, unless you're cruising in that rpm range. I might try raising the float to 14mm or going up on the MJ.

'91 GSF400
It's more fun to ride a slow bike fast than a fast bike slow.

Offline turbofb

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Jetting Thread
« Reply #7 on: August 29, 2007, 03:18:56 AM »
Heres my setup,it runs flawlessly at all temps and rips to redline with no hesitations or flatspots, so Id say that Factory Pro's setup list/guide is dead on for anyone in a similar environment.It ran horribly before the jet kit....

Factory Pro 1.0 jetkit in stock carbs,91 model Bandit 400........
97.5 main jet
3rd clip on FP needles/springs
15MM float height
stock pilot jets
2.25 turns on the screws,stable 1600rpm idle with a nice lope
Stock air box with K&N,lid perforated around the snorkle inlet
Yosh 4-2-1 headpipes with Hindle Stealth muffler
Iridium plugs,stock heatrange w/Accel wires
Sea level,average temps and humidity
Hot thermostat
I only waited 15 years, to buy a B4!!

Offline tomacGTi

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Re: Jetting Thread
« Reply #8 on: December 13, 2007, 11:25:05 AM »

Another read on jetting besides the Factory Pro way of doing it.

Another tidbit for those of you like me that have a Dynojet kit:

Width(thousands)------Kehein # -- DynoJets # -- Mikuni #
0,0350----              92,5--------- 92----------- 86,3
0,0360----              95----------- 94----------- 88,1
0,0370----              97,5--------- 96----------- 90,0
0,0380----              100---------- 98----------- 91,9
0,0390----              102,5------- 100---------- 93,8
0,0400----              105--------- 102---------- 95,6
0,0410----              107,5------- 104---------- 97,5
0,0420----              110--------- 106---------- 99,4
0,0430----              112,5------- 108--------- 101,3
0,0440----              115--------- 110--------- 103,1
0,0450----              117,5------- 112--------- 105,0
0,0460----              120--------- 114--------- 106,9
0,0470----              122,5------- 116--------- 108,8
0,0480----              125--------- 118--------- 110,6
0,0490----              127,5------- 120--------- 112,5
0,0500----              130--------- 122--------- 114,4
0,0510----              132,5------- 124--------- 116,3
0,0520----              135--------- 126--------- 118,1
0,0530----              137,5------- 128--------- 120,0
0,0540----              140--------- 130--------- 121,9
0,0550----              142,5------- 132--------- 123,8
0,0560----              145--------- 134--------- 125,6
0,0570----              147,5------- 136--------- 127,5
0,0580----              150--------- 138--------- 129,4
0,0590----              152,5------- 140--------- 131,3
0,0600----              155--------- 142--------- 133,1
0,0610----              157,5------- 144--------- 135,0
0,0620----              160--------- 146--------- 136,9
0,0630----              162,5------- 148--------- 138,8
0,0640----              165--------- 150--------- 140,6
0,0650----       167,5------- 152--------- 142,5
0,0660----       170--------- 154--------- 144,4
0,0670----       172,5------- 156--------- 146,3
0,0680----       175--------- 158--------- 148,1
0,0690----       177,5------- 160--------- 150,0
0,0700----       180--------- 162--------- 151,9
0,0710----       182,5------- 164--------- 153,8
0,0720----       185--------- 166--------- 155,6
0,0730----       187,5------- 168--------- 157,5
0,0740----       190--------- 170--------- 159,4
0,0750----       192,5------- 172--------- 161,3
0,0760----       195--------- 174--------- 163,1
0,0770----       197,5------- 176--------- 165,0
0,0780----       200--------- 178--------- 166,9
0,0790----       202,5------- 180--------- 168,8
0,0800----       205--------- 182--------- 170,6
0,0810----       207,5------- 184--------- 172,5
0,0820----       210--------- 186--------- 174,4
0,0830----       212,5------- 188--------- 176,3
0,0840----       215--------- 190--------- 178,1
0,0850----       217,5------- 192--------- 180,0
0,0860----       220--------- 194--------- 181,9
0,0870----       222,5------- 196--------- 183,7
0,0880----       225--------- 198--------- 185,6
0,0890----       227,5------- 200--------- 187,5

Here's the rub:Dynojet needles also have a known different taper and tip in comparison to Factory Pro needles and even more different yet versus than stock (both companies). They size their jets with the actual orofice diameter in inches versus the CC flow as Mikuni does. I know the website below is for an F650 but it's for reference sake, I didn't take a micrometer to my needles to confirm.

The shape of the needle seat is also slightly different for probably the same proprietary reasons. The OEM 102.5 is also known to be slightly bigger as well versus an aftermarket Mikuni 102.5. The Dynojet 100 (which comes in the jet kit) visually, has the same size orofice but more than likely has a seat designed for the DJ needle.

When the EPA tests bikes, they sniff them at highway speeds (probably 55) I'm guessing in top gear which is why the idle screws are as lean as they are and the mains as big as they are (to be "compliant " but still make some power). With the tighter taper of an aftermarket needle, it would only make that jet even richer since the hole is less covered at small openings. Obviously the higher the needle comes out of the seat, the more that flow number comes into play.

In the end, it comes down to what works. My bike is away for the winter now but I did make some changes to it that will probably affect the jetting come it's hibernation in the springtime. Putting all that schwah in here helps me remember it as well as hopefully will help a couple of you out as well.

Since this is a jetting thread here are my mods/numbers:

-Stock pilot
-Stock float height
-Did not drill the slides
-Stock slide springs (DJ ones would make the midrange flat)
-105 main (Mikuni)
-DJ needle, third position with one shim
-3.5 turns out
-Intake cam mod-not degreed
-Modified airbox lid with larger snorkel, no additional holes
-Removed silencer in collector
-Cobra F1S pipe with original core replaced with 2" perf'd stainless (more like an aftermarket pipe)

I haven't had a chance to really ride it with the pipe modded since the weather has come in now. Before with the smaller baffle (more than likely the reason why they say it's unnecessary to rejet), it made great power almost everywhere and was maybe a hair fat on the top end. With the free-er flowing baffle, it should theoretically even out and may have to go up on the main. We'll see come springtime.

Obviously everyone's bike is different but I'm mainly curious to see the jet sizes everyone has because they seem to be all over the place (for good reason: every setup is different).


Offline gsxr400 racer

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Re: Jetting Thread
« Reply #9 on: December 13, 2007, 01:47:22 PM »
this will turn into a even greater thread with time :beers:
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Offline Banditmax

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Re: Jetting Thread
« Reply #10 on: April 22, 2008, 01:23:53 PM »
I am now running
 Height above sea level: Around 750-1000 feet
 Outside Air temp: 14.1c
 Bike is: 1993 first gen non V model Japanese import. 33mm carbs.
 Engine Mods: In airbox K&N filter with standard lid. Waco full racing exhaust system without baffle installed. M-max derestrictor box. Carbs have just been fitted with all new o rings and floats.EDIT Fitted hotter thermostat now too.
 Needle: Factory Pro ti needles on 3rd clip down
 Main: 97.5
 Pilot: 32.5
 Mixture screw: 2 and 1/4 turns out
 Float height 15mm

Bike runs nicely and pulls strongly throughout.

Offline Tainted-Meat

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Re: Jetting Thread
« Reply #11 on: April 29, 2008, 03:50:27 PM »
Got a Bandit 400 Variable Valve,
 it's a 98 year and is completly standard

i am living not too high above sealevel and am needing some info on jetting, floats and what not.
good thread but needs some more info
gonna keet trying till i get it right

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Offline andrewsw

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Re: Jetting Thread
« Reply #12 on: April 30, 2008, 12:27:12 PM »
Instead of continuing to edit my old post, I thought I'd start fresh.

1993 400, Yosh 4-2-1, K&N filter in stock airbox with snorkel removed (anyone know if that's worthwhile? seems like it would cause more turbulence and possibly restrict more as a result... .02)

Main: 97.5
Pilot: stock, 32.5
Needle: Factory Pro, middle position
Float Position: 15mm
Air/fuel screw: 3.25 (still tweaking that)

Seems pretty good through out. I haven't done a good plug chop on the main yet, but I think it's pretty good. Pulls very strong in all gears.

Altitude typically 1500ft, very dry, cool average temperature.

Offline tomacGTi

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Re: Jetting Thread
« Reply #13 on: May 05, 2008, 11:00:33 AM »

Make your own conclusions, but I think that modifying outside parameters especially for something tuned to work a certain way may yeild less than stellar results.

Offline Thief400

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Re: Jetting Thread
« Reply #14 on: May 05, 2008, 11:41:12 AM »
That's an interesting read but when we had my engine on the dyno and a air pressure gauge hooked into the air box we had the most power with the snorkel removed and 2 extra holes in the lid. With the modified lid the engine made about 3 extra HP and the pressure was higher in the airbox meaning that there was less of a vacuum and more air.
That article only holds water if your bike is left stock, no pipes, no slipons, even the filter material makes a difference. And as any engineer know that there's the physics of how an engine works and there's the reality of how it works