2003 Bandit Starting/Running Help

[KillerGriller]

I have a 2003 Bandit 600 that only starts on choke, but dies with any throttle applied.

Fuel: When it does run or dies it smells super rich. I have pulled the carbs, cleaned, bench sync'd them, and adjusted the air/fuel mixture screws with no noticeable changes. Jets are clean/clear, floats and needles are set to stock settings and moving as the should.

Air: There's no change trying to run it with/without the air filter, and the engine revs higher when carb cleaner is sprayed into the airbox so I believe it's getting air

Electrical: Spark plugs are new, coils are good, all the connections seem to be clean/tight/functional, and I've tested it with two different batteries without any difference between the two. The resistance values of all the electrical bits are within spec. The signal generator is giving a low peak voltage (from two separate parts) which is the only measurement out of spec I can see so far, so I swapped it out with another one which unfortunately didn't change much.

My thought process: It's got fuel and air, so the spark must be the issue, but the only signal generator peak voltage is out of spec. (low) and it's didn't change when swapping in another part so the problem is upstream. The signal generator runs off then end of the crank, if the crank isn't turning over fast/hard enough it's not providing enough rotation to produce a strong signal. Why? Low compression? Weak spark?

Any suggestions? Or am I barking up the wrong tree?

[Suzukian]

That pick up doesn't produce energy like that, or work in that matter. It just senses a break in position to tell the CDI when to run. You could have a bad CDI, but they are pretty robust. How did this problem occur, instantly, or did it build up. Also, did you make sure there's no gas in your oil?

[Rijko]

Does your bike have a Throttle Position Sensor (small black box with wires coming out on the side of the carb rack), and did you check it ?

[KillerGriller]

That pick up doesn't produce energy like that, or work in that matter. It just senses a break in position to tell the CDI when to run. You could have a bad CDI, but they are pretty robust. How did this problem occur, instantly, or did it build up. Also, did you make sure there's no gas in your oil?

The manual includes the peak voltage test (to identify a bad signal genertor), yet both the stock SG and replacement are giving low voltage values so I'm trying to swim upstream to see what might be causing it? No, it doesn't produce energy but it does indicate the signal strength; my thinking is that if the singal is too weak or inconsistant the computer won't fire the spark plugs properly.

The bike was in pieces when I got it in the spring but supposedly ran fine before the PO took it apart so I'm not sure if it was acting up previusly or not.

Does your bike have a Throttle Position Sensor (small black box with wires coming out on the side of the carb rack), and did you check it ?

It does, but I tested/played with/cleaned it and it's working fine according to the diag.tests

[Suzukian]

Usually in these type of ignitions, the change of voltage from the trigger is what causes the CDI to fire. I'd follow the wires back and check them at the source. The could be a pinched or corroded wire degrading the strength or your CDI is bad, or you have bad grounds. Bad grounds are a big problem with Suzuki motorcycles with some grounds going to painted surfaces, and Suzuki relying on the threads to ground, which corrode, and you loose a ground, or it becomes weak. Check the fundamentals of the circuitry , clean every ground, and put a new end on every corroded wire. It could drive you nuts otherwise. My GS750ES ran the negative wire from the battery to the engine, and that surface was painted. When I unbolted it, the threads were all rusted. I purchased the bike brand new.

[limeex2]

It runs, so I would tend to rule out electrical components. Poor grounds of any type all need to eventually be cleaned/updated in any case, so fix them properly and that area can now be eliminated from a probable cause. Dont rule out the carbs or fuel yet. It could be an air leak which is very common on old bikes. I know it can get expensive, but having a forum carb guru go through your carbs can positively rule that out as a cause and give superior driveability once up and running. Sometimes fixing tough problems is not about finding the problem, but by eliminating probable causes that need attention regardless

[KillerGriller]

Thanks for the input fellas, I agree it's not a bad idea to check those grounds regardless of whether it's related or not. Talking with a mechanic relative of mine this past weekend his impression was that it's fuel/carb related, and suggested looking for air leaks as well. I'll give those a go and see what I can find. Cheers!

[pdqford]

[QUOTE=KillerGriller;

Fuel: When it does run or dies it smells super rich.

and the engine revs higher when carb cleaner is sprayed into the airbox
[/QUOTE]

Something doesn’t compute.
Is it super rich?
Or super lean?

[KillerGriller]

Something doesn’t compute.
Is it super rich?
Or super lean?

Good question, it's part of why I'm confused. Plugs are black when I pull them, there is some smoke, an it smells rich after it stalls, but it only starts on choke and revs high. (shrugs)

[Suzukian]

I would try running some Sea Foam through there, in the oil too. Bad grounds on these bikes came from the factory, they have ruined many ignition systems, and the problems are intermediate, till they finally give out, as Suzuki figured the threads where good enough for grounding, and they ground the battery tab to a painted surface on the engine. The corrosion on the thread is amazing to behold.