Unrideable GSX...

[Tez]

Before I get the tools out this coming weekend, I thought I'd drop by here to see if I'm going in the right direction. I ride an '89 GSX750ES with aftermarket 4-1 exhaust and K&N pods. I did have a Dynojet stage 1 just to keep me running until the stage 3 got installed. Well, done all that, adjusted the mixture and balanced the carbs and got a nice steady tickover. Blipping the throttle gave a healthy response with no hesitation. BUT...Took it out for a spin and once warm at low revs there is a lack of power as if there is a lack of fuel, and it gets steadily worse until it just will not pull away from a stop, the revs die to almost nothing. It will still idle at standstill, though not as steady as before. It was set at just over 1000rpm but once warm and these problems arise it idles at around 800rpm and I need plenty of gas to get a snail-like getaway. Not good in the middle of London traffic! Anyway, I am convinced that the carbs need stripping out again with a thorough cleaning of all jets and stuff. Am I going in the right direction? One other thing I noticed is that the three connections from the generator looked burnt, I have cleaned those up as much as I could. Would a dodgy generator cause grief as well?

[Road_Clam]

Before I get the tools out this coming weekend, I thought I'd drop by here to see if I'm going in the right direction. I ride an '89 GSX750ES with aftermarket 4-1 exhaust and K&N pods. I did have a Dynojet stage 1 just to keep me running until the stage 3 got installed. Well, done all that, adjusted the mixture and balanced the carbs and got a nice steady tickover. Blipping the throttle gave a healthy response with no hesitation. BUT...Took it out for a spin and once warm at low revs there is a lack of power as if there is a lack of fuel, and it gets steadily worse until it just will not pull away from a stop, the revs die to almost nothing. It will still idle at standstill, though not as steady as before. It was set at just over 1000rpm but once warm and these problems arise it idles at around 800rpm and I need plenty of gas to get a snail-like getaway. Not good in the middle of London traffic! Anyway, I am convinced that the carbs need stripping out again with a thorough cleaning of all jets and stuff. Am I going in the right direction? One other thing I noticed is that the three connections from the generator looked burnt, I have cleaned those up as much as I could. Would a dodgy generator cause grief as well?

Oh boy, another "Stage III w/ pods" nightmare experience. Do some searching with the key word "jetting" and you will archive a TON of input, some positive, MOST negitive with respect to adding pods. Simply sounds to me like you are WAY overjetted, and your bike is drowning in fuel...... Did your bike ever run good prior to the adding the stage III kit?

[fgh]

"One other thing I noticed is that the three connections from the generator looked burnt, I have cleaned those up as much as I could. Would a dodgy generator cause grief as well?"

These bike's generators don't produce enough current at idle to run the coils, it runs off the battery until about 2K rpm. If your generator has failed when the battery gets weak you could get the symptoms you describe. Check the charge in your battery and if it isn't fully charged then charge it up and give her a test ride.

[chef1366]

Pull your spark plugs when it's running poorly and see if your running rich. (black) If not check your fuel flow. (petcock or kinked fuel line) Your not running an inline fuel filter are you?

[KEITH KRAUSE]

As it warms up it does run richer, so it could be jetted too rich. But by your description if that rich I'd think there would be cold running problems too. Still a possibility. How is the jetting set up? We can possibly compare yours to others with same model/mods and see if your jetting is in the ballpark. We need stock jetting info and your complete set up...main jet, jet needle position, pilot fuel jet, pilot air jet, primary air jet if changed...
As part of jetting, the mixture screws must be set using the highest rpm method. I think you said you've done that??
Yes, if you have burning wiring, that will anneal the wiring/decease amperage flow and the end result is a weakened spark. Weak spark can have symptoms just like rich jetting, poor combustion.
It could also be venting related. An otherwise perfectly running bike can show fuel starvation within minutes if the gas tank isn't venting well or the floatbowl(s) have a venting obstruction.
Do obvious/simple things first. Gas cap venting, floatbowl venting is clear, and check out the Stator Papers info here and test to determine if you need a new stator or regulator/rectifier. If you didn't set the mixture screw using the highest rpm method, then do that too. Approx' 1 1/2 to 2 turns out is a typical starting point.

[Tez]

Thanks for all the advice, I am using a dynojet stage 3, with the circlip in the fourth groove from the top and dynojet 130 mains. The mixture screw I set by using something called a colortune...It's kind of like a see-thru spark plug and the mixture is adjusted to get a bunsen blue flame, although its only done at idle, and I was more concentrating on getting a blue flame rather than counting the number of turns. Neither am I running an inline filter. It was running a hell of a lot better on the stage 1, so I'm going to try and drop to the smaller dynojet mains after checking out the points you raised (probably at the weekend now...) and let you know how it goes. Thanks again!

[earlfor]

Check the voltage at the battery terminals with the engine running. If the connections from the stator and/or R/R are burned, thats a pretty sure sign of increased resistance and poor connections. If you do not have 12+ volts supplying the ignition system under all conditions/rpms, it is impossible and a complete waste of time to adjust/rejet the carbs.

Earl

[KEITH KRAUSE]

Thanks for all the advice, I am using a dynojet stage 3, with the circlip in the fourth groove from the top and dynojet 130 mains. It was running a hell of a lot better on the stage 1, so I'm going to try and drop to the smaller dynojet mains after checking out the points you raised (probably at the weekend now...) and let you know how it goes. Thanks again!

That jetting certainly doesn't sound excessively rich to me. The jet needle position is similar to many others with similar model/mods. The 130 DJ mains are too small if memory serves me right. That would be roughly equal to 120 to 122.5 Mikuni mains. Seems small, but what size were your stock mains? You running the stock carbs? What size are they?
If it ran a lot better with the ONLY change being the stage 1 to stage 3 transfer, that suggests the problem is jetting related.
But your problem is at low rpm, and I assume SMALLER throttle openings, correct? If the problem is at smaller throttle openings, then your main jet hasn't anything to do with the low rpm problem you describe. The main jet effects approx' 3/4 to full throttle performance. The jet needle position you currently have wouldn't cause it either in my opinion. It would most likely be the pilot circuit is operating poorly. It depends on what actual throttle position you're having the most trouble. That will narrow it down to what jetting circuit is giving you trouble.
Check the venting, etc, first because they should be checked anyway. But I think now that your pilot circuit is suspect.
PS: Another thought, check the choke plunger operation for fully closed/good sealing. Check choke cable slack too.

[KEITH KRAUSE]

Check the voltage at the battery terminals with the engine running. If the connections from the stator and/or R/R are burned, thats a pretty sure sign of increased resistance and poor connections. If you do not have 12+ volts supplying the ignition system under all conditions/rpms, it is impossible and a complete waste of time to adjust/rejet the carbs.

Earl

Right-o Earl. I did mention to check his electrical system out. Like you say, you can't re-jet if the spark is weak.

[Nicholaschase29]

I am also having almost the same problem. I have a gs700 EF with a supertrapp pipe and air filters. Although I do not have a dynojet kit there are 132.5 mains in it and #40 pilots. On top of that, I took out the orange washer/plug and added one thin regular washer about 1/6 the size of the orange plug, which raised the needle. Although I have done these carb mods, it really seems to be lacking alot of power. and it bogs/yawn at about 2500 rpm and you have to really open up the throttle to get it to clear up, where it still isnt making as much power as it should. I also seem to have that same problem with the bike running poorly after a bit of riding. Almost every time I come to a stop sign the bike dies as I coast to the sign. But it runs great in the grage and I adjusted mixture screws to highest idle.
The stock main jets are 122.5 and pilot jets are 37.5
also, I held the throttle in neutral at 2500 rmps for about 1 and 1/2 minutes, and checked the plugs and they were black, so I assume I am running rich but I have tried changing needle hight with no luck

I was thinking that the carbs could possibly be out of sync or floats incorrectly adjusted.
Thanks, I assume that our bikes are similar and pose similar problems.
Nick

[Tez]

Really appreciate all your info, on stage 1 I was running DJ120 Mains. Like you have said I really ought to check out the pilot circuit along with venting, voltages etc. I have a week off work next week so I'll get involved over the weekend and beyond and I'll update you as I go. Once again, thanks!