1200 Bandit running rough, carb problems

[slabsideB12Kent]

 

Thanks for taking the time to read what is one of the most posted questions on the internet regarding 1200 Bandits? (possibly)

Bought the bike recently after a 3 year break and im so happy, the suzuki engine is amazing. This is my third one.

When I test rode the bike all seemed well. After a week I found the carburettors needed balancing.

Balanced the carbs and found there was a 1000-3500 rpm flat/wobble spot while under load. So I raised the needle to the second clip and while things are better the revs through the 1000-3500 rpm range are erratic. So as I approach the apex of a bend with a closed throttle and open the throttle there is a serge in power at the apex that cannot be predicted. The idle is also alittle rough and if you open the throttle while in neutral the revs rise as the throttle is opened, if I then keep the throttle where it is the revs will slowly then increase. Choke is a nightmare but since I raised the needle the bike doesn't stall under breaking. If the bike idles for along time at a set of lights it becomes very difficult to regulate throttle and seems to "bog down". 

Bike has an Art rear can, has been "dynojetted" and has a K&N filter in the standard airbox. 

I'm going to look at the carbs this BH weekend. I'm thinking of a clean concentrating on the pilot jets, mixture screw settings and float bowl heights, while changing the air filter and needle height back to standard

Any more idea???

 

 

[Blubber]

Welcome to OSS. 

As for your question...best get your ass over to " general " and properly introduce yourself.  I've noticed that gets people a lot more helpier 

 

 

First round at the virtual bar is on you...btw 

Cheers 

[gsx]

BST 36 s . . . Emulsion tubes at a guess 

[wraith]

Welcome to OSS 

As @Blubbersays say hello in the general bit  and make shore you read the rules  (top of the general bit)

As to your question, did all this start after you balanced the carbs or before?

1-3000rpm is pilot jet.

[Foz]

Sounds like the pilot circuit needs a good clean

[Nik]

You say it's been dynojetted. Does that mean that your emulsion tubes and needles are Dynojet? My experience with Dynojet is that they are crap. Their parts are made from cheese, and wear severely. It could be the cause of your problems. 

Edited May 5, 2018 by Nik

[Bow]

Multitude of things to check.

check your pilot jets are clear, and all the pilot circuit is clear.  A squirt of carb cleaner through the system will show up any blockage.

needles,  are they smooth. Dynojet needles wear quickly, and once worn can cause over fueling off idle.

emulsion tubes,  has the venturi worn oval,  again,  over fueling off idle.

inlet rubbers,  are they cracked , seated properly, lean running issue.

spark plugs,  good indication on how the motor is running. Google it,  loads of info on the net.

hope this helps .

[slabsideB12Kent]

 

The advice is great thank you.

When I raised the needle I could see wear in the coating of the needle, not something I saw when I raised the needle on my 7/12 back in the day. 

I bought new standard pilot jets from Fowlers of bristol Wednesday morning and for £6 they turned up today (Thursday). Very happy. 

 

I'm going to fit them at the weekend and hopefully all will be well.

 

Thanks again for the advice, for those who care/need to know I will post again soon. 

 

Edited May 3, 2018 by slabsideB12Kent

[BanditStates]

On 5/3/2018 at 2:09 PM, slabsideB12Kent said:

 

The advice is great thank you.

When I raised the needle I could see wear in the coating of the needle, not something I saw when I raised the needle on my 7/12 back in the day. 

I bought new standard pilot jets from Fowlers of bristol Wednesday morning and for £6 they turned up today (Thursday). Very happy. 

 

I'm going to fit them at the weekend and hopefully all will be well.

 

Thanks again for the advice, for those who care/need to know I will post again soon. 

 

So did you get resolved?  Your last post was back in May and you said you would post agsin soon.

[slabsideB12Kent]

Sorry for the late reply, I found the carbs had a dynojet kit in them. I sonic cleaned them and then got banned so haven't got any further... 

[Askamaskinservice]

2 minutes ago, slabsideB12Kent said:

Sorry for the late reply, I found the carbs had a dynojet kit in them. I sonic cleaned them and then got banned so haven't got any further... 

So you got banned for sonic cleaning your carbs, that is a new one..........

[Gixer1460]

Just to stir the pot a bit for the DJ haters  DJ parts have a lifetime warranty - if they are worn, send them back for free replacement - Why won't Suzuki san do the same thing...........got a worn out GSXR here?

[slabsideB12Kent]

Driving ban lifted, i've been riding the bike again for a while now (2k miles).

During my driving ban I sonic cleaned the carbs, swapped the needles + springs back to standard (have another modified bike). The bike no longer has the issue of surging due to the original needles and needle springs being refitted. The main jets of the carburettors are not standard. Obviously balanced the carbs when I refitted them. 

I still have an issue with difficult cold starting and shaky running under low throttle. If the bikes run in the last few days it will start immediately or quickly. Give it 5 days plus and she just doesn't want to start. Takes around 4 bursts of 10 seconds of starting. When she starts it will backfire on choke and the RPM will jump around on the tachometer. During warming the bike will sometimes bog down from a  low throttle. Once up to temperature the bike pulls like a train but at very low throttle positions it jiggles back and forth. 

I'm wondering if it's the pilot screws? Possibly the bike is running rich/lean with a closed/partially opened throttle? Otherwise chain and sprockets?

No problem with excess fuel consumption. 

Any ideas?

 

Thanks, Chris

[Tombola]

[mark35gun]

just had a very similar problem , turned out to be the emusion tubes worn

dj lifetime warranty only covers the needles not the tubes

[slabsideB12Kent]

Bikes done 22k Miles. It's always had this issue though during my ownership. 

"mark35gun" worn emulsion tubes  is an interesting one.

I was thinking pilot screw setting (3.5 turns out) , float height (standard), chain and sprockets (runout) or fuel tap vacuum leak.

I have a spare set of carbs so I could rob the tubes from the other set, seems like this fault could be a slow burn...

[mark35gun]

i wouldn't, if they are worn you will end up chasing the fault, stick new ones in pref with new needles, you can ignore them if the fault still exists, you could not really tell mine were worn except with a vernier caliper, but they were, new ones sorted it.

my mixture screws are 2 1/2 out, i would set yours back to factory and go from there, but you won't sort anything if there are leaks from vac tap or carb rubbers,

misfiring? maybe, check plugs leads etc

[Tombola]

I have problems with my 2000 reg 1200s regarding fuelling as well, Absolute pig cold, and at low revs, points to this emulsion tube issue. be interesting to see if you get this sorted. 
 

I want to check for air leaks, balancing, valve clearance, as I doubt they have ever been checked.
 

where do you get these parts from? 

[mark35gun]

i got mine from dj, you will get them from robinsons

[Tombola]

I don’t know if I’m getting my wires crossed. I’m looking a DJ kits and it doesn’t look like it includes emulsions tubes.

I know these are for a 600 just checking I’m on the same page

 

[stellafella]

I get my carb parts from Allen's performance in Nottingham.

Good service and helpful

[mark35gun]

On 8/22/2020 at 4:05 PM, slabsideB12Kent said:

Driving ban lifted, i've been riding the bike again for a while now (2k miles).

During my driving ban I sonic cleaned the carbs, swapped the needles + springs back to standard (have another modified bike). The bike no longer has the issue of surging due to the original needles and needle springs being refitted. The main jets of the carburettors are not standard. Obviously balanced the carbs when I refitted them. 

I still have an issue with difficult cold starting and shaky running under low throttle. If the bikes run in the last few days it will start immediately or quickly. Give it 5 days plus and she just doesn't want to start. Takes around 4 bursts of 10 seconds of starting. When she starts it will backfire on choke and the RPM will jump around on the tachometer. During warming the bike will sometimes bog down from a  low throttle. Once up to temperature the bike pulls like a train but at very low throttle positions it jiggles back and forth. 

I'm wondering if it's the pilot screws? Possibly the bike is running rich/lean with a closed/partially opened throttle? Otherwise chain and sprockets?

No problem with excess fuel consumption. 

Any ideas?

 

Thanks, Chris

i thought you had removed the dj kit?

[slabsideB12Kent]

I did indeed remove the dyno jet kit (CV slide springs and needles), replaced the main jet with the standard ones and used a carbtec kit to replace all rubber o rings the running of the bike improved. 

After I refitted the carbs the bike ran better but I have erratic idle and "surging/wobble" at small throttle openings. If I adjust the idle screw it changes the nature of the surging and moves it in the rpm range. The bike  runs rough on choke, idle speed fluctuates, it can bog down on occasion during warm up. 

It's looking like I will have to remove the carbs again and replace the emulsion tubes to rule them out, as well as check the valve clearances.

The saga continues...

Edited October 15, 2020 by slabsideB12Kent

[Reinhoud]

Too lazy/drunk to read everything;

 

- Check valve clearance

- Condition of spark plugs

- check synchronisation of carburetors

 

 

[Dezza]

You may have 2 problems. The poor starting sounds like some of the very fine cold start drillings that go up from the float bowls are blocked. This can occur in the float bowl drillings, the carb drillings or both, and can make cold starting a pain in the backside for obvious reasons. The other symptoms sound like blocked pilot jets/drillings. Personally, I'd strip the whole lot (including splitting the bank) and soak it all in acetone/thinners for a couple of days, then ultra-sonic 2 or 3 times, then rebuild with new O'rings.