1996 Suzuki Bandit 600 S weird RPM jumping problem.
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- เผยแพร่เมื่อ 2 ต.ค. 2024
- We've been scratching our heads about this one for a while.
The bike idles perfectly.
Above 2600 RPMs the bike runs perfectly.
At /exactly/ 1600 RPMs it jumps to 2600 RPMS regardless of what we have done to alter it.
Here's what we've done:
. new petcock.
. fresh fuel.
. now using a aux tank with a fuel filter just to eliminate the tank.
. new air filter.
. carbs separated, thoroughly cleaned (chemical dip and then heated ultra sound cleaner), reassembled with new gaskets and carefully balanced using a calibrated carb balancer.
(same result with second carb rail)
. clean jets. (we even have a brand new oversized replacement set of new idle jets no joy)
. clean idle circuit bypass ports (as far as we can tell by pouring fluid through them)
. new floats and needles.
. no vacuum leaks that we can find anywhere.
. new plugs correctly gapped.
. valves adjusted.
. firing on all cylinders.
. compression of 150PSI on all cylinders warm.
. leakdown test left gauge on leakdown tester set to 90 on a 100PSI source. Right gauge when cylinder at TDC read between 84 and 87 across the cylinders.
. resistance check on both coils within spec
. battery voltage at 12.7V when the bike is off. 14.72 @ 5000 RPM (too high?)
. problem occurs at about 1/16th throttle opening so the slides and mains aren't even in play yet.
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I have the same bike
that (throttle adjuster) you used is for fine tuning slack in cable did you properly set it below on the carbs. if you have it too tight it could jump.
you check valve clearance.
did you sync left side to right carbs?
any of your CV diaphram cracked
did you bench set all screws?
are you missing any springs?
is your idle set screw bent or missing spring?
are all your vacuum ports blocked while testing?
I can't get mine to idle down I've did the cable adjustment and idle screw dont change anything running 2200 Rpm can't get it to go any lower
Worth checking the jet needles, as they then wear as they rub against the emulsion tubes in the carbs, other than that the only other thing would be the throttle position sensor?
Check the Haynes manual for the checks recommended at your mileage
I couldnt clean my jets on inside.....so I soaked them in gas and lit them on fire. Worked like a charm. No longer clogged.
Thanks for posting.
Yea, we got a spare ignition module and tried that without any change. One mechanic I talked to suggested that the jump could be tuned out by adjusting the length of the carb rail breather tubes but we've been unable to get that to work either.
Interestingly, we've looked at 3 bandits of the same vintage and they all exhibit this same problem. At this point, we're just living with it.
Have you checked your float bowl hight? If the fuel level in the bowl is incorrect the main jet perhaps gets "false" air\fuel? I would have tried to go either 1mm down (or up) from the original setting. Which I think is 17mm. Best of luck
I have the same problem and have tried the same things and my bike still runs up to almost three grand
We never did figure out what the cause was. We looked at another Bandit that exhibited the same behavior. Warping of the butterflies? Dunno. :(
It sounds like untill 1600 rpm not all your cilinders are running, and when you have enough throttle the other cilinder joins the running club. So proly one of your carbs is set up differently then the others or is very dirty.
Unplug the tps
Could it be related to different jets ? Idle Jet, Main jet and pilot jet? Just bought a gsf 600 and carburetors are a mess..
Did you ever figure out the problem? I don't have this problem with mine but just out of curiosity? Also my bike doesn't seem to idle as smoothly as yours seems to be hunting a little bit and doesn't like idling when cold, will have to ride a fair few miles to get it warmed up to the point it'll idle without dying when cold. Only thing I haven't done to it is clean the carbs out but seems to be running fine other than that.
+Michael Whitney We never did conclusively figure out what's causing it. The best guess we have is that the butterfly plates might be slightly worn letting some air through or maybe the bodies themselves have warped a little bit due to age and that's causing air to get by. Not sure, just guessing. My buddy has just learned to live with it.
It sounds like you need to balance your carbs.
@@YermoLamers sounds like he needs to clean them. You sound like you need to clean yours too. It's the words we don't want to hear. I payed $300 to get mine done and then it sat up for 2 years and all the money was wasted lol. My bandit runs like a bag of shite and I'm spending a fortune on tools to fix it all lol. Got all the tools to do it and more on the way, but I'm just a lazy cunt, it's cold currently and I can't be bothered. There's your answer lol.
Thank you so much for all your input I been through the carburetors two times but I've only check the float height one time so I'm going to go back and do floats again maybe I got something wrong. The fuel being too high in the bowls makes sense. The second time I went to the carburetors I separated them and replaced all the o-rings I also I have not sink them and dialed in each side together. I feel confident that one of these or the combination is it . I also have been through the valve twice and I have them dead on. Thanks again for all the input
Be safe happy riding Paul
Sticking or partly blocked jets maybe?
Just had my carbs ultra sonic cleaned (cost £120 inc labour) & they were very blocked due to bike standing for 2 years.
I actually bought an ultra-sound cleaner for exactly that purpose. :)
hi, i have a bandit and i have some problem like this. I'm running on normal rpm example 5000rpm i go up increase the rpm but sometimes my rpm is decreases or stays the same, and the bike feels like somebody is holding it. Do you have any idea what is it? The gas is clean, i don't have water in carbs. thank you for your time.
***** That could be caused by so many things. I'd probably check the rubber boots at the top of the carb over the sliders for dry rotting/cracking. I'd see if the sliders are sticking at all.
Thank you for the tip, i will check and i will get back to you.
did you try the vacuum diaphragm under the petrol tank, can buy kits online,
We replaced the petcock which had a new diaphragm. Good idea, though.
Were you solved this problem yet?
Did you even heard about carbs synchronising?
Yup. the carbs are synced as close as we can possibly get them. Same problem exists on 3 others bandits we've looked at. It's very weird.
Yermo Lamers How about spark's threads? Are they ok on every each cylinder?
194Easy Oh that's a good suggestion. I can see how that might cause it. But yes, we did check the spark threads, did both compression and leakdown tests.
that is completly normal, since when its idling its using idle jets and when you throtle up abit the main jets are openned which gives more fuel and air and rpm jumps abit like in this video
Borrow another Ignition Module and test with it it. Might be a ignition mapping issue?
Does it also happens on higher revvs, or on revv down?
Voltage seems right as manual states - generator max power is around that rpm.
Also check on the right side, in front of the clutch cover, the ignition position sensor.
Yea, we swapped the ignition module as well. Interestingly, 3 other bandits we've looked at all exhibit the same symptom.
Yermo Lamers Really weird... If it's not ignition related, it has to be something in the carbs. Maybe the "butterflies" are sticking, or the springs or jets are not to spec. Were the carbs tuned/rejetted? Maybe those 3 bandits were serviced with the same incorrect part. The carb breathers cant play a part on that, its too precise. Does it also happen when riding? Like, if it starts "pushing" more, over the 1600rpms?
***** We cleaned the carbs, two sets, and put new jets (and everything else) in them. It jumps from 1600 to 2500 every time but after that the bike runs perfectly.
We spent some months trying to track this down to figure it out. Some have suggested it's just endemic to this model since some people who own these bikes have said it doesn't happen but then you ask them to try to keep the RPMs at 1700 and they realize they can't.
My buddy has been riding his bike now and compensating for the jump to the point that he now almost doesn't notice it. It just sounds like he's revving it a bit high when launching.
Did you ever check the TPS?
It's carbureted so doesn't have a throttle position sensor to my knowledge. Our best guess was it had something to do with the butterfly valves in the carbs but he eventually just decided to get used to it and rode the bike for years that way.
@@YermoLamers Weird, mine has a TPS. Mine is a Mk2.
@@williamfoster4268 huh. Then that's something I missed. If I ever see that bike again I will definitely check that out. Thank you!
Unbalanced carbs?
Carbs are balanced as close as we can possibly get them (unless we've done something wrong in the process). But over two carb rails the exact same problems exists. Interestingly, we came across another bandit of the same year which exhibited the exact same problem. We're suspecting something age related but have no clue yet what it might be. valves, plugs, carbs, sync, filter, vacuum leak checks, etc etc. Moving on to replace the brain box.