Bandit 1200 fueling issues

[banditdan123]

Evening all. Can't seem to get my. carbs set correctly under 4000rpm. I've had the bike on the dyno and it's reading rich and a flat spot until 4000rpm? After 4K it's spot on! Idle mixture screws seem to be best set at 2 turns out. Any help would be grately apprieciatd! 

[FJD]

fuel level maybe too high ?

or a sticking float, or leaking float seat O-rings

[bluedog59]

Have you taken the snorkel out of the airbox ?  

[dupersunc]

Don't go below 4000rpm.

You have not been charged for this advice.

[banditdan123]

It's running dual pod filters, tried lowering float height and found it made no effect? It is a bit stutery at 2000-2500 in first and second gear which becomes less noticeable when you're in 4th and fifth gear. It will sit fine in top gear at 2500 but will take until 4000 to pick up. Everything is fine on the dyno after 4000. 

[banditdan123]

Yes that has been suggested. Lol. 

[bluedog59]

If the a/f ratio on the dyno says it's rich then weaken it off. lower the needle a clip or half with a thin shim or maybe in on the air screws or down on the pilots.

All presuming everything else is serviceable and correct.

[banditdan123]

Will try a size down on the pilots. It's got 42.5 in at the moment. A/f ratio good from 4000 - redline. 

[Scara]

On 24/05/2017 at 4:58 AM, banditdan123 said:

Evening all. Can't seem to get my. carbs set correctly under 4000rpm. I've had the bike on the dyno and it's reading rich and a flat spot until 4000rpm? After 4K it's spot on! Idle mixture screws seem to be best set at 2 turns out. Any help would be grately apprieciatd! 

Would be nice to know just what the dyno readings for the AF ratio is.

Sounds like a couple of things could be going wrong here. If I may,

1). Carbs have been re-jetted incorrectly

2). Main jets too large and engine cannot disperse excess fuel below 4,000

3). Vacuum or air leak between air box and engine - carb boots, air lines, cracks etc.

4). Float level still incorrect.

Generally with air pods fitted, mains re-jetting is required to match both pods and pipes and a minor adjustment on the e clip.

Normally mains are enriched slightly to compensate by going the next jet size up - example #115 to #117.5

If a dynajet kit has been fitted then setup could be completely wrong. Its real easy to make a mistake with one of those kits.

Down sizing the pilots  doesnt seem to be the area you need to look at. If its idling ok, and you blip the throttle and hesitates on the rev before it comes down, its lean. On the other hand, if it comes down nice and dips, then bogs and comes back up to idle again, its rich. Simply turning the mixture screws one carb at a time will rectify that.

Carbs are a black art and any adjustments should be made one at a time. A mass correction could give you wrong signals and you start looking in all the wrong places.

best thing to do, is write down the current settings you have - check it with the book spec - correct it to default settings if the bike is unmodified and make your adjustments from there providing yourself with a good firm benchmark. Write down what effects your adjustments make to bike performance at differing rev ranges.

If re-jetting must be done, always always start at the main jet(s) first. Fit mains which will provide proper AF readings at WOT. If you dont do this first, anything else you do will be a complete waste of your time.

Happy to help out as you progress, keen to hear how it turns out.

 

Edited May 27, 2017 by Scara

[Wee Man]

Have you checked emulsion tubes for wear?

[banditdan123]

Hi there  Thanks for the reply. The engine is modified its a 1200 bandit with a ported gsxr 750 dot head and cams. It's also got an ignition advancer and dyna 2000 ingnition with dyna coils and leads. I have a set of bst38ss carbs that have standard needles with clip in second groove from top float levels are set to standard level 14.6. They have 42.5 pilot jet and all seals etc have been changed and the needles, emulsion tubes, float valves and seats were replaced around 500-800 miles ago. As above pilot screw is 2 turns out. 

[suzook12]

From memory, think  pilot jet should be #40, mixture screws 2- 2.5 turns out

[banditdan123]

Have put #40 pilot jets in and will hopefully have some dyno time soon. 

[Antman]

Hi 

I would be looking at using different needles with all those mods.

Get yourself a factory pro config 3.0 kit .

Give Marc at Factory Pro an email if the kit is NLA he can still make one up for you.

Did do for me on the 750.

 

[banditdan123]

I have been looking for a factory pro kit but haven't seen one listed. Do you have an email address for him? Many thanks. 

[Platpoep]

 

I would like to inquire about this part below, indicated with a red arrow, this is for a Bandit 1200 GSF year model 1997.

Can you please explain to me, what part of a carb kit is meant to be attached to this hole indicated with a red arrow?

is it the IDLE JET / Pilot JET?

I have been told that this is damaged to no repair and that a new carb kit can not be installed because of this one part/screw tread, indicated with a red arrow.

If possible can you please advise a new course of action?

 

Kind regards,

M Lunacek

[clivegto]

7 hours ago, Platpoep said:

 

I would like to inquire about this part below, indicated with a red arrow, this is for a Bandit 1200 GSF year model 1997.

Can you please explain to me, what part of a carb kit is meant to be attached to this hole indicated with a red arrow?

is it the IDLE JET / Pilot JET?

I have been told that this is damaged to no repair and that a new carb kit can not be installed because of this one part/screw tread, indicated with a red arrow.

If possible can you please advise a new course of action?

 

Kind regards,

M Lunacek

What

[wraith]

Hi pic is not there, and be nice if you said hello and started his own thread instead of using a 5 year old one 

Edited August 31, 2022 by wraith