Running Rich...

[UtterChaos]

Hi guys,
I got a running rich problem that's been bugging me for ages.  I get 85 miles from a tank of juice, a smell of petrol, sooty plugs and smoke and high revs.

Setup –

'97 Bandit 1200
Straight through can - Scorpion.
K’n’N filter in original box (with extra 2“ hole)
100.2 mains (standard?)
Dunno what needles but they’re in 2nd notch down with only one shim.
Screws are 1¼ out (didn’t need to drill ‘em - UK spec.!)
132bhp at the crank.

-  by all accounts it should be lean as hell!

I recently dropped the needles to top groove in an effort to cure it, the bottom of the revs got smoother (I think ‘cos carbon was burnt off of the plugs) but I’ve lost power mid range and top, still smokes at revs and still drinks gas – will change back!

I also ran it with no filter to see if the slides would lift – they still did which (apparently) suggests a modification to the slides (drilled?) – and it still ran rich!

I don’t want to loose any horses, but 85 mile range? … I’ve got to do something!

Cheers,

James

Annwn B.C.

[smooth operator]

I can't imagine it running rich with 100.2 mains in.(102.5 is stock) I'm running 150s for mains40 piolots,K&N pods and although I only get 100 miles per tank,its burning good.
  Start with a new set of plugs
 NGK- Cold: JR10B
         stock: JR9B
         hot:   JR8B
  Autolite- stock:4143 or #4162
  Champion- RA6HC #809
  Bosch- XR4CS
  Make sure your float hieghts are set properly, 14.7mm is the recomended hieght. Then have the carbs synced with a pair of gages.
   I'm thinking your floats are off, I'd start there and the plugs and then see what happens.
          Dan

[smooth operator]

Correction- The Autolite for the 1st Gen. is #4143,the Champion-#905 RA4HC. The other ones were for the 2nd Gen. Bandit.

[Red01]

FWIW - Dale/Holeshot recommends the Autolite 4162 for all B12's.

[UtterChaos]

Sorry guys, 102 mains it is ....

[pmackie]

Check a couple of things:
1. Float height
2. Float needles and seats.

If you using that much fuel, you may have one or more carbs running fuel through the engine due to the fuel level in the carbs being way to high. I'd check the float needles and seats for leaks/damage and check the float height while I was there.

Make sure the air filter is clean...

[UtterChaos]

OK .. so .. just come back from the garage.

I’ve now acquired another set of carbs and some KnN twins.  My new carbs have cylindrical needles – apparently the norm, whereas my old needles are tapered!

Here’s what I’ve done and what happened.

Fitted standard needles and twin KnNs – result bike ran but stalled as soon as you touch the throttle. – even the smallest blip on the throttle and the engine died.

So, changed back to the tapered needles but left the KnNs on – then ran out of time and rode the 25 miles home unable to rev over 6000 revs!

What the hell are tapered needle – and why are they in my bike !?

Why wont it run without ‘em?

- all this and I still only have 102.4 mains …. I think something is very wrong ..

HELP!  

James

[smooth operator]

I'm thinking your too lean. The bike ran befor with the stock air box, now your giving it more air with the pods,and its starving for fuel.(I'm a tile setter,not a technician)
  Dale Walker sold the tappered needles with his jet kit.I'm not sure about Ivan's,Dyno jet needles.I have Dales tappered needles in mine. It would be a way of adjusting the amount of fuel be delivered durring throttle opening.(still just a dumb tile setter, not a technician)
 In Fastlarry's FAQ from Bandits R US, with just a after markey can, you could run the stock mains but shim the needles. Once you did the hole in the air box mod,add a K&N filter,tappered needles, the chart shows 127.5 mains. And heres the part I don't get, going down in the pilots to 35s. I don't understand why they go down in the pilots,with the smaller piolots mine pops through the exhaust at low speed and seems to starve for fuel. I have the stock piolots in.
  Then when you add more air into the equation with the K&N pods, you go up to the 150 mains(thats what I'm running)w/ full exhaust and again I don't understand but go down to 32.5 piolots needles @2/3 from full rich(mine is 1.5 from full lean,by using a washer to get the .5)and screws 2.75-3.5 out(I'm @ 3)
   Now this is just a tilesetters quess, I have been wrong befor. Once I thought I was wrong,but I was just mistaken. But I think it needs more fuel.   Dan

[okbandit]

You have a jet kit of some sort.  I am assuming that you bought it used.  It would be helpful to identify what kit you have.  The number of clip slots in the needles is a clue as well as the air box condition when you started (any holes and where-what size).  An ivan kit will have a bunch of small holes in the lid, around 20 at 3/8 diameter.  Not sure about the HS kit as mine is a stage 2 with pods, but the needles are black with 5 slots.  If you can identify what you have you can go back to the base settings.

[okbandit]

Once I reread my post I remembered something I read.  If I remember correctly, doesn't the dynojet kit use a different jet numbering system then everybody else?

[Red01]

Once I reread my post I remembered something I read.  If I remember correctly, doesn't the dynojet kit use a different jet numbering system then everybody else?

Yes, in part because they use their own jets and everybody else uses OEM (Mikuni, Keihin, etc.) jets.

[wiredgeorge]

Dynajet jet needles are long and thin with little taper. Stock Mikuni jet needles are more likely stubbier in appearance with more taper.

The bike was using aftermarket jet needles that are killing your gas mileage. Get a set of stock jet needles and toss the aftermarket. The second set of carbs likely had stock jet needles which were likely lean off throttle. The reason wasn't the jet needles but the pilot circuit. You will need a larger set of pilot jets (which never come in Dynajet jet kits). Adjust your mixture screws as well... at idle, adjust each in turn for max idle speed. Should be a couple turns out I am guessing.

In any case, once you get the bike to idle and come off idle OK after installing larger pilots, see if the bike will pull redline cleanly. If the mains are too small, it surely won't. If they are grossly overlarge, it surely won't. Ever hear of a plug chop? Make sure you are using Mikuni main jets. Start at a size where the results will be meaningful with your set up. If you are using K&N filters and a slip on, go up perhaps 15 points over the stock size... on a Mikuni main jet of #102.5 that would be around a #117.5. Then buy a new set of plugs in the correct heat range. Put them in your pocket and find a deserted stretch of road. With the bike warmed up, go to the side of the road and install the new plugs. Start the bike and open the throttle wide open in 3rd or 4th gear and try running at LEAST a 1/2 mile and then hit your kill switch and coast to the side of the road. If you can't get to redline, go as high an rpm as  you can and sustain it for 1/2 mile.

Hit the kill switch, coast to the side of the road. The burn on the new plugs will reflect the air/fuel mixture at wide open throttle. Pull the plugs and if they are white, the mixture is lean and you will need to install larger main jets. If the mixture is black, you need to install smaller main jets. If the plugs are cardboard colored, the mixture is fine.

Once you have the idle and off-idle transition sorted and the correct main jets, fiddle with the mid-range. If your bike is baffled, you shouldn't have to make much adjustment, if any. If it lacks back pressure, then you MAY have to shim the jet needles. Mikuni makes .5mm shims which is about 1/2 a normal step size for jet needles with slots. I would guess you won't have to shim but could well be wrong. If you find a flat spot, usually between 4-6K rpm, then use two shims and see if that makes the flat spot disappear.

[dgc]

awesome.  thanks for all the input, i am currently dealing with a similar problem myself.