2000 1200 carb issues

[Wrider]

Hey all.  I was here a long while ago when I was attempting to resuscitate an old B400, which went unsuccessfully due to a fried ECU and cracked/bent frame.

Anyway my sister just sold her 09 Ninja 250 and bought a 00 Bandit 1200 (yeah, huge upgrade, I know).  She bought it and it runs ok, but the carbs definitely need dialed in and I was hoping y'all could help.

First off we're in Colorado Springs at 6000 ft.  Secondly it has a Holeshot Stage 2 kit installed.  It has the 147.5 mains.  It has the 35 pilots.  It has the K&N pod filters.  And it has a 2 Brothers slipon.

So here's the problem.  It runs like a raped ape as long as you're on it.  But idle and engine braking it backfires horribly and doesn't idle worth a darn.

FWIW I am a bike mechanic, but I have no experience with this particular bike and am all ears knowing how a lot of bikes run fairly particularly.

So here's the lowdown on it.  Idle adjustment screw (who decided to put it there anyway?) has been played with.  I don't have access to my carb sync tool but I eyeballed it when they were off and are pretty close.  Idle is 2000-2500 RPM while backfiring horribly.  Any lower and it slowly slows down and dies.  It also likes to backfire into the carbs and blow off the vacuum caps.

What I'm thinking...
1. Needs a carb sync obviously.
2. Needs a valve adjustment.
3. Open for ideas to get it running better.

Any advice you guys give me will be greatly appreciated!

[Wrider]

Bump

[wizzobeer]

If you have access to a stock air box I would try that. From what I recall, most kits recommend staying away from pods.

[Wrider]

Unfortunately I don't have access to one.  I've done some reading and it seems the pod filters do alright.  It's seeming like it needs a carb sync and it's possible I need emulsion tubes as well.

Any other ideas?

[Big_Jim59]

Sounds like you are running a bit rich on the idle circuit. Does it stink like a 70 vintage Chrysler when it runs? Does it start cold with no choke? Does it surge at steady throttle openings? That popping back, at closed throttle, could be unburned fuel. Try turning the pilot screws in a quarter turn at a time and see if the condition improves. Also, sync the carbs. You won't get to first base if the are not pulling up together. A buddy of mine has a B12 and he has his dialed in pretty close but we are a lot closer to sea lever here in the flat lands of Texas.

[Wrider]

So I finally got my manometer in and balanced the carbs.  Boy oh boy were they off.  Carb 4 had about 13 cm of vacuum while carb 3 had 2, carb 2 had 5, and carb 1 had 3.  Way off.

Anyway it's running better now.  I need to get back into the slides and move the needles back to the 3rd position, but 2 works for now.

[rider123]

yeah sync will help a lot, otherwise you're going to have lazy cylinders which will show up lean on a plug check. Once it's semi-synced I would drive around at low throttle openings(the problem area) and do a quick plug check. The plugs wont lie and will tell you where you need to go on the mixture screw settings. How many turns out are you now? Usually backfiring and jerkyness is attributed to LEAN pilot settings not rich. You may want to try turning out the mixture screws 1/8th to 1/4 out just to see if the problem gets better or worse. You can always turn them back.

[LowRyter]

I am guessing that you're running lean with #35 pilots.  Which is odd since you're in the mountain.  My 98 B12 did the same, fattened up the pilots and actually went down on the mains (home made failed st 1 attempt).

After many miles & carb rebuild we got the st 1 dialed in and opened the hole cut in the air box.

despite all that 3 of 4 plugs show rich but it runs pretty well. 

[Wrider]

Sorry I thought I replied to this.

Ended up being a sync issue.  I synced the carbs, made sure the vacuum lines were all on there, and it runs great now.