poor idle

[dbcanh]

Hi all, i am a newbie, my name is paul and i live in york in the UK, i have a idle problem with a bandit 600n 1995, the bike struggles to tick over evenly, starts ok, it runs ok at high speed, pulls well, but tick over is up and down, feels like engines going to die when i stop at lights or in traffic, I have put new plugs in, tryed silkolene pro fst, new oil and filter. Is this a idle jet block problem? its doing my head in, i really don`t want to take carbs off!! if i can help it. Been reading about that seafoam carb cleaner, any thoughts? help on this would be great,  oh yeah before i forget took it back to dealers he said it was ok? or a lazzy rev counter!! you could see the needle dropping up and down, he reckoned he balanced the carbs he said they were spot on? they put new plugs in has well.

just started bike up tonight and i sprayed brake cleaner (the stuff that evaporates) round the intake rubbers near to the engine...........and the idle went up to where it should for a few minutes running evenly!! until the stuff evaporated, did this 5 times, same thing again! there must be a leak in rubber manifolds or a crack, going to take tank off and tighten every thing, and have a good look tomorrow may be `o` rings in manifold? keep every one posted tomorrow.

Been i shed in the cold messing with this, tank off, got engine running with another petrol source, tightened manifold clips, checked various hoses, but still poor idle, took air filter out ran it, a bit better, but still erratic. funny thing is i blew though the air tubes which go to the t junctions at bottom of the carbs, and the tick over was ok for 15 mins so i put everthing back together, and bike was still running poor, although the tick over  was not dropping right off has before. Anyway went back to dealers today sat, he told me to bring the bandit back Tuesday, and they will look at it its still under( warrenty). this has done my head in!! i will let you know how i get on.

[mosquito]

I'm not familiar with your model, but those symptoms sound like symptoms I had.  I finally got it running reasonably by cleaning the carbs, especially the idle jets, properly adjusting float heights, and getting the idle screws set right.

*But* that also sounds like you're on the right track finding vacuum leaks first.

[apollonrop]

I have a 93 Suzuki Katana with similar issues.  Originally, I was having issues with power thru the entire range.  But now after cleaning the carbs I have gotten power back thru the entire upper rpm range 7k+.  Unfortunately, since I bought the bike and have been working on the carbs the damn thing never runs smoothly at idle.  In fact, when I slow down for a stop sign or red light most of the time it will stall and stop running.  This is most troubling, and it has forced me to take extreme measures.  That is to say that I have even completed a valve job, leak down test and compression test.  Officially, the engine is sound so I know my problem is all carbs. 

I have tried everything I can think of.  Let me know what you guys can think of that might help and I'll tell you if I have tried it. 

[dbcanh]

hi there, yeah mines ok at high running speed, but will not tick over, rev counter needle up and down, its in the workshop has we speak, has its still under warranty.  i reckon its either, idle jet block?, or rubber manifold leak? or poor tappet adjust? we shall see what the mechanic says.

[dbcanh]

Got bike back today being Thursday, the shop took carbs off and cleaned jets, he said they were clean has were the float bowls, and set mixture screws checked carbs for balance again must be forth time, i`ve done them twice, they put new air filter in. in my opinion its no better? i said the bike was a cold arse thing to warm up, he agreed having started it up from cold, he said there was some rev counter needle fluctuation but he reckons that was normal for a bandit? We discussed about not running the tank right down on reserve, has he reckons the fuel pressures not has good has a full tank?. So there you have it from a qailified mechanic.

[Dink_1170]

Add Seafoam to the next couple of tanks. If that doesnt help, pull the carbs yourself and clean ALL the passage ways. BTW you got suckered!!! a GRAVITY fed fuel system uses the force of GRAVITY not the weight of fuel to feed the system; so no change to system pressure between top to reserve on the tank.

Dink

[dbcanh]

The mechanic told me not to use any fuel cleaners /additives, there usually pretty good mechanics has ive had bike from the same dealer before no problems, he pulled the carbs he had bike for 3 days!! it was there idea to bring it in!.

[r_outsider]

Seafoam works just fine, people use it on everything from old farm tractors to new cars with all manner of electronic engine and emission controls, I've never heard of anyone having a problem with it.

As for your problem, did you fix the vacuum leak? You identified the problem with the brake cleaner, plus a bike that needs forever to warm up is most likely running really lean, also pointing to a vacuum leak. The carbs themselves are probably either fixed or a secondary problem at this point. Replace the intake pipe gaskets (and the intake pipes themselves, if they look cracked) or at least get some silicone gasket in there for the time being and everything will probably be right in your world again.

Given the age of the bike, changing out most of the rubber fuel system parts probably wouldn't be a bad idea either.

[apollonrop]

hey db,

So look I have had some of the issues your describing.  I just yesterday learned that my carbs have these removable piston valve holders that secure the needle jet and jet needles.  Mine were filthy and clogged.  For my bike this was what was messing my system up.  I think that you might have the same issue.  I agree with Dink and Outsider.  If you have a vac leak you need to find it and replace the rubber.  Use WD-40 or some other sprayable ether to test for leaks.  While your bike is running, I suggest you squirt one carb at a time; this way its alot easier to find the leak if there is one.  If that doesn't work then you can rule out that rubber being your issue.  If you find the leak and repair it you may not need to do much more than just recalibrate the carbs.  The fuel/air ratio would have been set on the old vac leak lean ratings so you want to correct for that.  But if this doesn't solve the problem, then its time to open them up and get your hands dirty.  You also could have some seals that have gone bad in the carbs, like float seals or needle jet assemblies grommets that aren't working (although given your symptoms its probably not a flooding issue).

Now the other thing, generally your tank is vacuum and gravity driven as Dink mentioned.  If your tank has a petcock that is probably your problem as they are really crappy and go bad all the time.  They can inhibit proper pressure from getting to the carbs (this could also be a sign that your float levels are wrong either too low or high depending on your float layout).  If not, the only concern you should have about running on low fuel is tank debris getting into the carbs.  While the specific gravity of gas changes with temperature, the way tanks are designed generally ensures that there is enough pressure for the system to work properly...until your tank runs empty.  

Now the last thing.  Using a fuel stabilizer/carb cleaning fuel additive is generally a good idea.  I don't know any mechanic worth his salt that would not suggest using some at some point in time.  Unless he is trying to run some sort of test he didn't tell you about...maybe a plug chop test.   It doesn't sound like that is what he is doing.  Now before you play the "loyalty to my mechanic" card, I would remind you that if this guy can't fix this problem in 2 tries its time to find a new one who can or do it yourself.  There are good mechanics who solve your problems and then there are bad ones to justify why they can't.  And FYI (for your info) if your idle is messed up, you should realize that the issue has to do with your carbs' idle circuits i.e. the pilot system, throttle valve, and the needle jet system (assuming the engine is right, a leak down and compression test can verify if your bike has bigger issues than carbs; although the carbs are the #1 thing that gets messed up, generally not the engine).   These are the areas you need to focus on in order to isolate and repair the problem (assuming that there is no vac leak).  Take a look at this web page and you'll see where and what systems correlate with the rpms you are having issues with. http://www.dansmc.com/carb_jet_usage1.jpg.  This comes from http://www.dansmc.com/carbs2.htm. 

Finally, not related to your bike in anyway, the word "as" is spelled "AS" not "HAS".  The second spelling is for possessive descriptions; like:  "He has a carb", or "he has carb issues".  Not the other way, the way your using it, i.e. "has he reckons the fuel pressures not has good has a full tank?" <-- your post from the other day.  You meant to write "AS he reckons...not AS good AS a full tank...".  Instead "HAS he reckons...not HAS good HAS a full tank" makes no sense.  Sorry took me forever to figure out what you were saying.

Anyway, try the ether vacuum leak approach first, if that doesn't work then open up your carbs and check the three systems I mentioned.  Be prepared to shell out some cash for new seals once you open the carbs up.  Unless you have already replaced some of the seals recently.
GOOD LUCK!

[smooth operator]

Seafoam works just fine, people use it on everything from old farm tractors to new cars with all manner of electronic engine and emission controls, I've never heard of anyone having a problem with it.

As for your problem, did you fix the vacuum leak? You identified the problem with the brake cleaner, plus a bike that needs forever to warm up is most likely running really lean, also pointing to a vacuum leak. The carbs themselves are probably either fixed or a secondary problem at this point. Replace the intake pipe gaskets (and the intake pipes themselves, if they look cracked) or at least get some silicone gasket in there for the time being and everything will probably be right in your world again.

Given the age of the bike, changing out most of the rubber fuel system parts probably wouldn't be a bad idea either.

  that would be my quess too.

[dbcanh]

Hi again, well i pulled the carbs off bandit.......and took the float bowls off........and first thing i noticed was the float heights 2 were up and two were flat to top of carbs (upside down on table) So i am trying to get my float heights right, this is my third attempt today at this, my eyes are going bogeyed!!. the manual for bandit 600 says 17mm + - 1mm from float bowl joint, is there any pictures? video of someone doing this on a bandit, yours Paul.

[dbcanh]

 I am having a right Nightmare time, set floats in the carbs to 17mm height.  also had the motor cycle shop check them, fitted carbs back to bike myself, and.. fired it up, and petrol was pissing out of one of the breather tubes!! oh shit, not good, white smoke then blue would not run, only on 2 cylinders. i also put new inlet manifolds rubber o rings on. either the float height is too high on two of the carbs or ?. Trip back to the suzuki center to have a word with them, i have to take it back in again to get sorted has i have totally fu@K it up, my wife played hell with," me saying i should not have messed with it in the first place!!" (but it would not tick over properly in the first place ) but least it was running?  .

[dbcanh]

One last chance at bike before i take it back to shop, carbs off, again. sprayed float needles, put carbs back on, bike fired up not leaking petrol this time!, running really ropey, still wont tick over!! talk about making a bad job worse!! back to the Suzuki Center it goes Friday, It`s done my head in lucky its still under warranty by a few weeks! Had to have a word with the bosses son who said it was ok after i had meddled with it!! . Been snowing here in uk, had to push the motorcycle in the snow 8cm deep!! lucky there only up the road from where i live.

[dbcanh]

Mechanic phoned me up to pick bike up Saturday about 4pm, we had a chat, about the floats he said they were still ok, he said the carbs wanted balancing again Must be the 5th time they have been done!! he said i had done nothing wrong with the carbs had he cleaned them and blew jets out again, running  now?? .Had a right job trying to get the thing home, compacted snow and ice, good job its only down road from my house.

[apollonrop]

hey Paul,

Sorry I didn't get back to you sooner.  I haven't been on much on account of traveling.  So first things first if your still working on fixing the bike.  To balance floats you need, or at least I find it easiest to use, a flat head screw driver.  What I do is I use a ruler to measure (in your case) 17 mm from the tip of the screw driver inward and then I use a pen to create a hash mark on the screw driver.  I use a screw driver bc it is easy for me to visually see where I'm at float wise and how to adjust accordingly, you can use a Vernier clip, (i think that's how its spelled) and it does the same thing but its even easier bc it can be fixed at what ever height you want to measure (I'm cheap so this is what I do). 

Now unfortunately float adjustments are tricky so I'll be as clear as possible.  As you probably have realized when your adjusting the floats your actually adjusting the needle seat in the float mechanism itself, thereby moderating the amount of fuel coming into the float bowl at any given time.  So in order to get it right you have to measure the floats from the carb body until that needle actually seals.  If any of these seats are worn or have groves in them this principle wont work.  So check them first and replace them if necessary, better to be safe than sorry here, replace them if there is a question.  Most mechanics will then tilt the carbs until the float they are looking at seals or settles into its port.  Does that make sense?  Then they will measure the height of the float from the end of the carb housing where the float bowl attaches to the tip of the float its self, and not the float body...the actual movable part itself.  So to recap, you measure the float height from the carb body where the float cover attaches to the highest point of the moving floats i.e. the apex of the rounded float (in my case...yours might be different). 

But your not done.  In order to determine if your getting the right fuel mixture you would want to do a plug chop test.  That is, you would want to start the bike, then run it at around 60% throttle either in any gear for about a mile or in nuetral for about 1-2 minutes.  Then you pull your spark plugs on each cylinder one by one.  If you have black spark plugs then you know the fuel is burning rich and you can still make that float a little tighter i.e. 18 mm instead of 17mm (what happens is the more fuel in the float the more opportunity and more importantly the less pressure it takes for the fuel to get sucked into the engine).  You want all the cylinders to have the exact same pressure when the petrol ignites i.e. you want the right amount of fuel entering into each cylinder based on both the cylinder's pressure losses (from wear and tear) and the carbs themselves.  Generally the carbs should be doing or allowing the same amount of fuel into the cylinders unless maybe a seal is a little more worn in one (or more) carbs than the others for example.  This is why carbs are adjustable, so that you can accommodate for engine wear and tear.  IN OTHER WORDS JUST BC THE BOOK SAYS 17MM DOESN'T MEAN YOUR BIKE NEEDS 17MM ON THAT PARTICULAR PISTON.  But generally we assume it does and that's why we start from that measurement. 

Regardless of the bike the plug chop test is how you have to proceed.  If your spark plugs are white than your fuel mixture is too lean and needs the floats need to be changed closer to 16mm or possibly 15mm for example.  When you run the bike lean you will see that white smoke you mentioned from the exhaust.  If the spark plugs are chocolate color then your there.  You got them right.  Now once that is finished you still need to do this same test for the idle and quarter throttle positions.  I suggest you start with the idle for 3-5 minutes and adjust the idle mix screws to coordinate.  The quarter throttle test measures the needle jet and jet needles and is a bit easier to correct, so well get to that if you do the test (assuming that these first two tests haven't solved your problems).  This is a long task but when you get all your spark plugs right...your tick over will be much better and so will the performance of your bike. 

Hopefully this helps you if your still at it.  Good luck.