Answers from Ivan

[China Greg]

There's been a number of references to Ivan's jet kits/needles, and I had previously promised a visit to his shop when I returned to NY from China.

I visited him today at his small shop in Congers, NY; he was very busy setting up an SV650 race bike,.. but we're old aquaintances, and he chatted with me for a few minutes concerning B12 carb set-ups.

He re-iterated: STAY WITH THE INSTRUCTIONS. He said that he's sold a lot of kits for the Bandit series, with excellent customer satisfaction, (he inferred that if complaints are around the Net, they MAY be generated in part by competitors for commercial reasons). The only problems [he claims] seem to arise when people get too far away from accepted equipment or settings.

So again, with BOTH of my FIRST GENERATION (1997-2000) models that I've had, this is what the key set-up seems to be, producing a crisp, idle-to redline curve [note: This is with a Yoshimura RS3 end-can]:

MAINS:  117.5
PILOTS:  37.5
NEEDLES: second clip down from top. No extra shim.
AIRBOX:  (20) 1/2" (?? check this diameter on your instructions) holes in the top back of the box, rubber snorkel removed
FUEL SCREWS:  YES up to FOUR turns out! Ivan says that those screws regulate the VOLUME of fuel-air mixture.. not the actual mixture pecentages as in old 2-strokes, for example. If you can run those screws OPEN, then so much the better.. means More Flow down Low. He guesses you can open those screws up as much as FIVE TURNS before they lose effectiveness.
As always, check your plugs for proper burn color.

My pervious fuel screw settings were actually 3-3/4 turns out; I'm going to clean out the pilots all carefully, then turn all out to a full four turns, and see how it goes.

Also, I had really bad results when my air-filters got even a little dirty, so I replace them at least once per season.
I was in the mountains of New Mexico on my first Bandit and it ran BLACK until I changed the filter...which didn't look that dirty... just a little gray. After the change, it was like a new bike. Just a head's-up on that.

Now, Ivan noted that on some exhaust systems that had LARGER DIAMETER header pipes.. (e.g., a D&D FULL system), you might need to add a shim under the needle... but in general, he agreed with my settings above.

Lately I have found a touch of white or gray on the plugs (tips only). My bike often sits for months at a time, and he asked how is it running around idle? I said, recently a tad stumbly. He suggests to make good and sure there's no GUM in the pilots, as modern gasolines have additives that gum up fast.


Report on results in a week or so, after I have knee surgery (I was teaching a Chinese biker club how to do wheelies on the beach south of Shanghai... when I had had to DAB heavily on the edge of the surf, and well,, now tomorrow it's time for Amelican O-to-pedic Docta Man with Knife)

PS- In regards to the newer 1250 Bandits (which are fuel-injected), Ivan says they may need a "TRE" [?] change... he thinks there are power limiters computed in for the lower gears. He offers anyone with a 1250 in the lower NY region to contact him... as he thinks he may have a plug-in TRE by-pass to fit... but at moment has had no B-1250 customers come in.

Generally, Ivan is a good guy and gets my respect... a little over-worked (and sometimes over-stressed; I wouldn't want to work for him.. he's a perfectionist). But he really does have a great brain for tuning, and has always been available for me (as long as my questions are brief!).

No, unfortunately I'm not getting any commission here...

[PitterB4]

Awesome post, Greg.  Thanks and welcome home!

[Rocketjock]

Dammit Greg. Now you've got me going over and over mine for answers. I just emailed Ivan a detailed letter on my "problem" which I guess is really kinda minor. That 2 to 4 grand rough running thing. But, I guess if you are going to do race mods to your bike, you shouldn't expect it to run normal in cruise mod. One thing I asked him about tho, was why I even did the airbox mod when the instructions seem to indicate that I could have run the stock needles with only the rubber duct removed. "Intended for use with stock header and aftermarket slipon." is what the instructions say.

[China Greg]

Rock/Jock- Once again, note that you have a SECOND Gen. Bandit... so a lot of the carb settings aren't the same as 1st Gen.
(for you F.I. guys... yer on your own!)
------------
Here's a little bit of "Jetting 101" theory, for anyone out there maybe without tons of jetting experience, (and please, anyone is welcome to correct me! I'm certainly not an "A" mechanic!)

Mid-range problems: remember, we're not usually talking about RPM levels as much as THROTTLE position. A 3000 rpm stumble while "cruising" isn't necessarily the same problem as a power-curve "flat-spot" when nailing the throttle wide open. You'll have to try and identify out when and where the "problem" comes on.

Basic throttle openings vs. fuel circuits-

1. WIDE OPEN  :Mains
2. HALF-OPEN PLUS : Mains and needles
3. CRUISE   :Mostly needles, some mains, some pilots
4. OFF-IDLE  :mostly needles and pilots, influenced somewhat by fuel screws
5. IDLE  :Pilots and fuel screws

Each overlaps the other to a different degree.

Jetting is such a pain in the azz (for me)... always has been... but it's SO WORTH IT when you finally get it sorted out properly and the bike is suddenly CRISP across the total rev range, with no flat spots. (And after all, isn't that so much more desireable than just saying "IT'S FASTER NOW"?) 
Unfortunately, unless you're lucky, it usually takes a lot of trial and error to get it really sweet. (PS.. it may be a good idea to buy extra intake / airbox clamps because you may wear-out the screw heads after a while, if you're doing a lot of repeated carb-removal. The rubber intake boots might also eventually get stretched or cracked).

Investigating:
Start at the Top with your best-guess main jet size. Warm the bike up really good, and on a SAFELY deserted stretch of open road, whack it WFO wide-f&*$ing-open for 2-3 gears.  Assuming it runs smoothly (no bogging or stumbling, hit the kill switch, coast to a stop, and check the plug color of a plug...looking for LIGHT TAN, of course. When that's good, work your way down to the needles, checking smoothness at mid-throttle openings and slow roll-on. Make adjustments if necessary... moving the little C-clip "UP" will cause a leaner condition; "DOWN" will mak it  richer. Go lower to the pilots if necessary (but most pilots in my bikes haven't needed changing that I can remember). In the end, fine-tune the low-throttle openings with detailed fuel-screw adjustments (usually 1/4-turn increments at a time). Eventually, you'll get it. Just make sure other things aren't affecting your results, like dirty air-filters, mis-adjusted valves, or poorly-synched carbs.
TAKE NOTES on each change you make. You WILL forget, otherwise.

I had an Asia-only Honda 400SF in China, to which I added a carbon-fiber end can meant for a GSXR 750 (NEW condition, off EBay for only $80!), then chucked the clunky airbox in favor of individual Unipod filters. But no matter what I did after that, I COULDN'T get it to run. Barking, belching, spitting, stalling. Took me WEEKS and it was just driving me crazy, ran horribly and I was about to give up and go back to stock.. until some online-Aussie genius recommended a BIG jump in main-jet size. I ended going up a full, incredible FIFTY PERCENT larger on the main-jet sizes, and man, DID it EVER run!! That little F%*#er SCREAMED... probably picked up a whopping 15% power increase over stock. Suddenly, it was like a rat-monkey with it's ass on fire. I almost creamed myself when it finally howled to life cleanly. DAMN that thing would RIP across the Chinese farm roads. Loud and raspy as hell with that big, open D&D pipe... good thing the cops over there had no time for such details. PS..I did almost NOTHING to the bottom fuel circuitry; used stock needles and pilots... mostly just some fuel-screw tinkering.

Point is here, keep trying. Read all the stuff you can find on jetting...over-lapping fuel circuits, etc... how one affects the other... and ONLY MAKE ONE CHANGE AT A TIME, or you'll go nuts and never figure out what worked and what didn't.

Yes, it SUCKS to keep ripping that bank of carbs in and out, over and over... but you'll get better/faster at it, I asssure you.

[Rocketjock]

Greg. It's interesting that you run your first gen with second gen screw settings while other people with first gens talk about 2 to 3 turn settings. Lately it's been Snowfrog who runs a Yosh with the clips set at middle position. I have owned Yosh's before and it seems to me that 2Bros may have a bigger hole. Perhaps that's the difference.