Bandit 1200s Idle issues

[DaneJurrous]

Hello fellow bandito's! I am new to the forum and to my fairly newly purchased 2002 Bandit 1200s. Has been a blast of a bike although has had a slight issue start to rear its head and I would like to get it figured out before gets too far gone. Here is the jist of it. When the bike gets warmer and if I am driving stop and go traffic the bike starts to run at a higher idle then normal upwards of 2000-2200 RPM's, normally around 1500 or so. I was thinking it could be a an air leak around the carbs causing it to run lean at an idle? Has anyone else encountered anything like this and/or would my thinking on the air leak be a possible cause?

Any input greatly appreciated, these newer bikes are a bit out of my area of knowledge since my old bike is a 1981 gs750l I am turning into a Cafe racer.

[rider123]

COuld be an air leak. BTW it should be idling around 1200 rpm or so 1500 is a little high and will be hard on the tranny going into gear. If you want to see if you have an airleak go get some "quickstart" spray ethyl alcohol and run the bike on the centre stand and spray around the boots. If the RPM goes up, then you have an airleak. It could be as simple as just tightening the boots as over the years they will get a little loose. I wouldn't run around too much without figuring it out as you don't want to burn a valve or a piston. You could also check the plugs. If one of them is super white looking that might be the culprit. I would guess airleak before jetting though that is possible. Are the mixture screws drilled out? You could try a 1/4 turn out on the mixture screws if you're pretty sure it's not a vacuum leak or gummed up pilots. Because gummed up pilot jets will lean the bike at idle as well. Try the easy test first and see if it's an air leak.

Is the bike stock or jetted? Stock they are lean as hell normally and a drilling of the mixture screws and/or exhaust and jetting really opens them up. Hell even just drilling my mixture screws out when it was bone stock and turning them out 1/4 turn really smoothed out the bike and gave me a few ponies to boot. Do a plug check and post the pics if possible here.

[DaneJurrous]

Thanks for the response Rider! I have been a bit busy lately working on the 750 cafe project so I have not been really checked into it yet but I will tonight! Right now I think it is stock jetting as it has a stock can and filter on it. Have not seen any other modifications on it that I can tell. I did look the other night and can see some cracks forming on the plastic intake boots small but could be part of the issue.

I will get the idle down to the correct RPM and see what I can find with a little quickstart will do. Are the air boxes very difficult to get out on these?

[txbanditrydr]

If the RPM goes up, then you have an airleak. It could be as simple as just tightening the boots as over the years they will get a little loose.

FYI... Don't over-tighten either.  That too can cause an airleak.

[rider123]

Good point. If the ends of the clamps are touching it's too tight, they should have at least 2-3 mm of clearance between the ends. I have them around 3 mm roughly and I've taken the carbs off a bunch of times and I'm fine. Also keep in mind that as the bike warms up the idle will climb a bit. Best to adjust the idle when it is fully warmed up, at least 30 mins of riding. It could be that the bike is simply warming up and at that high idle rpm its just climbing naturally. You may be fine, but just slightly lean if it's stock and high on the standard idle.

I've never removed the airbox but the general consensus is they are a bit of a bitch to get out but doable. If you're going to completely can the airbox for pods I guess you could cut it out to make it easier.

[DaneJurrous]

Ok well I did the test of getting it warm, rode it up the canyon for about an hour, sprayed some "quickstart" around the boots and did not make any changes.  I don't think it is just normal warm up, although a valid thought, because I can ride it for an hour pull to a stop have it idling at 1500 rpms stays there for about 20 seconds and with my hands off the throttle it will rev up to 2000-2200 2seconds later. Would the PAIR systems have any effect on idle speed?

[pmackie]

Would the PAIR systems have any effect on idle speed

Shouldn't...it's pushing air into the exhaust pipe, after the engine has done it's thing

More likely o-rings in carbs, idle jet/air screw issues.

[DaneJurrous]

Well after a weekend out of town I am back to try and figure this beast out.

Shouldn't...it's pushing air into the exhaust pipe, after the engine has done it's thing

More likely o-rings in carbs, idle jet/air screw issues.

Thanks Pmackie I was hoping that would not be the issue but guess I will have 8 carbs being pulled apart on my bench. Guess I should clean the other bench off so I am not inadvertently putting my 750 jets in the 1200, would not be a good day. I have also been thinking I should check the valve clearance as well so might be a good time to do that to make sure all is as it should be.

[rider123]

Just for fun you could take out the pilot jets and make sure they are clean and not gummed up. The best way to make sure they aren't varnished up with bad gas is to take a few windings from some picture hanging wire or some other wire and work it through the pilots. What the hell while the float bowls are off you might as well clean the mains while you're at it. Also maybe check the float height and make sure there isn't any crud on the needle seats. Generally carburetors just don't "break", but if they get gummy from old gas over the years it makes them run a little wonky. I'm sure a good clean will clear it up and at the minimum give you a piece of mind that the carbs are all good inside afterwards. For float heights they should be 13mm for your bike. If you need help you can always ask here. And please adjust the idle down to 1200 or so! Your poor tranny....

Here are some examples of what causes lean idle and what doesn't to help you out:


Causes of lean idle:
Leaky exhaust manifolds
leaky intake boots.
gummed up pilot jets
gummed up needle seats/needles
improperly set float height(too high)

Not Causes of lean idle:
PAIR System
Ignition issues
loose chain
paint color
handlebar tassles
global warming
fluoridation of water
sunspots


I hope this helps, let us know how it goes. I'm sure a good clean will fix you right up. You don't need to pull the airbox to get the carbs out if that's what you were asking a few posts back. Just loosen the 2 top bolts on the airbox and the seat lug assembly and when the boots are loosened you can pull the airbox back enough that the carbs will slide right out.

[DaneJurrous]

Just for fun you could take out the pilot jets and make sure they are clean and not gummed up. The best way to make sure they aren't varnished up with bad gas is to take a few windings from some picture hanging wire or some other wire and work it through the pilots. What the hell while the float bowls are off you might as well clean the mains while you're at it. Also maybe check the float height and make sure there isn't any crud on the needle seats. Generally carburetors just don't "break", but if they get gummy from old gas over the years it makes them run a little wonky. I'm sure a good clean will clear it up and at the minimum give you a piece of mind that the carbs are all good inside afterwards. For float heights they should be 13mm for your bike. If you need help you can always ask here. And please adjust the idle down to 1200 or so! Your poor tranny....

Here are some examples of what causes lean idle and what doesn't to help you out:


Causes of lean idle:
Leaky exhaust manifolds
leaky intake boots.
gummed up pilot jets
gummed up needle seats/needles
improperly set float height(too high)

Not Causes of lean idle:
PAIR System
Ignition issues
loose chain
paint color
handlebar tassles
global warming
fluoridation of water
sunspots


I hope this helps, let us know how it goes. I'm sure a good clean will fix you right up. You don't need to pull the airbox to get the carbs out if that's what you were asking a few posts back. Just loosen the 2 top bolts on the airbox and the seat lug assembly and when the boots are loosened you can pull the airbox back enough that the carbs will slide right out.

I did adjust the idle down thought that was a pretty quick and easy fix to make sure I do not cause any further issues  As for the info  I figured it was going to come down to a carb rebuild and clean which is fine I am just finishing the one up on my old bike so I will start on it in the next day or so. You are correct I was asking about the airbox because on my 750 you have to fight to get the carbs or the airbox out on that dang thing, which will now have pods and a new jet kit. I had not really delved into the whole pair system to figure out how it works so I thought why not ask, I may end up getting rid of it but who knows, not needed in my state.

How are handle bar tassles not a issue of a lean idle? Buddy had some on his Harley which was running rough and we removed them and could finally hit 80 MPH but that could be because I was pushing him with the bandit ha ha!

[rider123]

Maybe the handle bar tassles were causing too much air friction! Any little bit will help a Harley! lol!

My guess is that the carbs are a little gummy. If you want to be lazy sometimes putting some seafoam in the tank and running a few tankfulls through will clear it up. Might be worth a shot since you already have a project. Go for a long ride then do an Italian tune up to create a shitload of vacuum on the pilots might just clear it up.

Italian tune up(old Dell'Orto carb trick)

Rev the bike on the center stand to around 6000 rpm then let off the throttle and cover the intake hole at the same time. This creates a shitload of vaccuum which will suck up any crud up and out the carbs. You'll have to take off the document tray to get to the intake snorkle, that and some seafoam through the tank might save you a shitload of time taking the carbs off.