Hey everyone, :frustrated: :whatever: :smoke:
I am back to cry here, in my comfort space. Amongst you guys...
Despite going through a mental breakdown since the weekend, I'll try to write everything in a cohesive manner...
Please bear with me. :smoke: :smoke: :sad:
I will reply to this post the AI summarized version, in case this is too much...
So, I was planning to post my success story in Idling Issues (https://gsx1400owners.org/forum/index.php?topic=7518.0) started by Will.
I was complaining about my fast idle not engaging fully/properly. I even took a video to celebrate with you.
Key information:
For TBs 1&2, the spring that supports valve to open fell of the assembly, cause I was stupid and I was using that to open the TVs...
Referring to this spring #15 in the schema (https://oem-bike-parts.pl/en/parts/suzuki/1099cc/gsx-1400/gsx1400-k2/14-throttle-body-model-k2).
I instead put something that was solid and had the same height and was working alright. That was the condition of the bike when I balanced it later on.
I purchased a Healtech Vacuum Balancing Tool (https://www.healtech-electronics.com/products/est/). Quality is great, software is alright. Price is pricey.
I did balance my TBs, they were quite off, running lean, bike popping.
Temperatures in Warsaw during my balancing, ~10c to ~15c. According to my JMP Oil Temp Gauge, oil was >60c <80c during tune-up.
For 2 weeks, the bike was spotless!
Lovely, beautiful, running nice and smooth and it would start at ~1000 to ~1100 RPM and it would keep RPMs beautifully, running like a well tuned piano.
So even with that shitty solution I had for my TB 1&2, bike was iddling, accelerating, and pushing alright.
However, it hadn't cured my Fast Idle issue.
Regardless, this is not my issue right now. The fast idle is the least of my concerns right now.
Post two weeks of me enjoying my bike running smoothly, at some point, after a brief traffic light stop, I noticed RPMs dropping slightly to ~900RPM, indicating bike was choking/running rich.
I tried to bring it back, but the black knob adjuster wouldn't budge, and I put some extra pressure and I rotated it clockwise, and it did move slightly and brought the RPMs back.
I didn't think about it much, as long as it brought my RPM back up.
After that I had a lovely 270km trip around Poland, and I even found a good stretch of road and pushed the bike to its limits ~225km/h on GPS ~250km/h on the Speedo, with intense headwinds.
A couple of days later, went for a group ride with the bois and the weather was warmer than usual, maybe ~23c maybe ~26c.
As soon as I started my bike parked outside, stayed relatively warm, I noticed a relatively low idle, the bike even stalled on me while I was practicing my uturns in the parking lot.
I started adjusting the black knob to fix the idle and as soon as it hit ~1200RPM and I would bleep it, it wouldn't come down normaly, it would indicate a vacuum leak, as the RPM would hang before coming back down.
I felt horrible. I abandoned the group ride and starting riding back home, via the highway. All good, bike was pulling, running ok all the time until at some point, it just started bogging, losing all power <4k RPM.
Long story short, I found a relatively safe place to stop on the emergency lane (God Bless EU for having those on highways) and I see my makeshift junk piece resting on my alternator, indicating that whenever I was twisting the throttle in low RPM, only Cylinders 3&4 would get air, thus the bike was bogging until the metal thing would start to ABRUPTLY, touch cylinders 1&2. A kind man stopped, helped me, we fixed it. I had to take the vacuum hose out of cylinder 1 temporarily out, to fit the piece back in and ride home.
CRUCIAL PART:
I forgot to reconnect cylinder vac hose 1 back on, and it was the scariest ride to my home ever. intermitent power, unexpected surges of throttle, etc... did shat myself a couple of times on the bends ...
I realized after maybe 15min of riding, reconnected it, bike behaved ok to the garage.
I went to the garage, and I thought, hm, let me balance my TBs again. I hook the bike up, the bike is like 99% spot on. I started heating it up, to see if it was a heat cycle issue. Revved it a bit, left it to idle, while tinker to go from 99% to 100% via adjustments. It was the first time I heard the fan working. I shut down the bike briefly after it was perfectly balanced.
When I tried to start it again, maybe 2h later as I was frustrated by the spring situation and I was trying to fit a proper spring in that TV position, the bike was running the same as the group ride. Erratic idle, and very low with no room to adjust with black knob. Yet again, I tried adjusting it, and then it completely unscrewed itself from its position. I lost the spring (look in schema numbers 13/11/12) (https://oem-bike-parts.pl/en/parts/suzuki/1099cc/gsx-1400/gsx1400-k2/14-throttle-body-model-k2). I tried starting the bike and it was lumping, running extremely lean, popping constantly, I was afraid it would backfire strongly. I started removing the coils, one by one, while mainting some ~1800RPM throttle by hand cause essentially I had no idle, and nothing would happen when I would remove cyl lead #1. All the rest, the engine would behave like shit, trying to die. I wanted to fix the issue by messing with the screw between TB 1&2 + 3&4 that is used to balance the bodies together, it also fell off. Luckily, I didn't lose this one...
Now, if you managed to read this far, you're a champ and I wish you great prosperity in your life, cause you're curious enough to help a desperate fella! (I hate feeling helpless).
Noteworthy that I didn't mention above, I rarely leave the bike on the side stand, but sometimes when I do, I get a check on the dash, I assume is the TIP OVER SENSOR, when I bring it up, it goes away.
During this tragic day, when I restarted my bike, I saw a brief check as well.
1. What would cause my bike to have the slight drop in RPMs at the traffic light?
2. What happened when I 'overtorqued' the black know clockwise and fixed the idle? Did I move it off of its sitting?
3. Was this overtorquing the reason that when I restarted my bike during the group ride that the idle was even lower and then when I adjusted it, it was so lean, it felt like a vacuum leak?
4. Would the ECU record some shit data while I was riding the bike during the errors I had, and now it has shit in its memory?
5. How should I tackle this now? What do I do first? Obviously, I will try to fit in the i) black know screw in its place, then ii) the TB balacing screw, iii) then try to balance the TBs while the bike will be warm >60c on the oil temp gauge.
6. Should I clear the ECU from the crap with the method you describe in the forum?
7. Any advice, I am happy to receive it guys...
AI SHORTER VERSION
---
Hey everyone, :frustrated: :whatever: :smoke:
Back again... unfortunately not with a success story this time. I'll try to keep this clear. :sad:
I originally wanted to post in Idling](https://gsx1400owners.org/forum/index.php?topic=7518.0]Idling) Issues (http://[https://gsx1400owners.org/forum/index.php?topic=7518.0), as I had mostly solved my bike's behavior (except fast idle).
Key info:
For TBs 1&2, spring #15 fell out (schema (http://[https://oem-bike-parts.pl/en/parts/suzuki/1099cc/gsx-1400/gsx1400-k2/14-throttle-body-model-k2)(https://oem-bike-parts.pl/en/parts/suzuki/1099cc/gsx-1400/gsx1400-k2/14-throttle-body-model-k2]schema[/url)]).
I replaced it with a solid makeshift piece. Bike was later balanced in this condition.
Used a Healtech](https://www.healtech-electronics.com/products/est/]Healtech) Vacuum Balancing Tool (http://[https://www.healtech-electronics.com/products/est/) — TBs were off, running lean, popping.
After balancing: bike ran perfectly for ~2 weeks (smooth idle ~1000–1100 RPM, strong pull).
Even with the temporary fix, performance was fine — fast idle still not fixed.
Then problems started:
* Idle dropped (~900 RPM) at a traffic light → adjusted black knob (tight at first, forced slightly → RPM recovered).
* Did a 270 km trip, bike ran great (even ~225 km/h GPS).
A few days later (warmer weather):
* Low idle, stalling, unstable RPM.
* Adjusting black knob caused hanging RPM (like vacuum leak).
* On ride home: severe bogging <4k RPM.
Found root issue on roadside:
* My makeshift piece fell out → only cylinders 3&4 getting air intermittently.
* Fixed temporarily with help, but forgot to reconnect vacuum hose on cyl 1 → extremely unstable/throttle surging ride home.
* Reconnected → bike somewhat OK.
Garage situation got worse:
* TB balance was ~99% fine initially.
* After heat cycle → erratic idle again.
* Black idle knob unscrewed completely → lost spring (schema](https://oem-bike-parts.pl/en/parts/suzuki/1099cc/gsx-1400/gsx1400-k2/14-throttle-body-model-k2]schema) 13/11/12 (http://[https://oem-bike-parts.pl/en/parts/suzuki/1099cc/gsx-1400/gsx1400-k2/14-throttle-body-model-k2)).
* Bike now: no idle, very lean, popping.
* Cylinder test: cyl #1 no change when unplugged → likely not contributing.
* Also loosened TB sync screw (between 1–2 and 3–4), but still have it.
Questions:
1. What caused the initial idle drop?
2. Did forcing the black knob damage/misalign it?
3. Could that cause the later lean/vacuum-like symptoms?
4. Could ECU have learned bad data from all this?
5. Best recovery order:
i) fix idle knob assembly
ii) reinstall TB sync screw
iii) rebalance TBs warm (>60°C oil)
6. Should I reset ECU?
7. Any advice appreciated — I'm a bit lost here.
Firstly forget about the ECU, they don't remember anything. Not even fault codes, they're very basic. It's barely more than a CDI that also does fueling.
I think in your place I'd replace the vacuum lines, including the one to the PAIRS of still fitted. They go brittle with age and split, that causes terrible running at low revs and it sounds like you'd disturbed them which is when they normally fail. They are 3.2mm ID, a common size and you need about 800mm of hose to do them all. Just be careful not to snap the T-pieces, although those are solid in a lot of car parts places too.
Look under the throttle bodies and you'll see where the idle adjustment cable goes. It's unlikely you've damaged it but you'll see where the throttle quadrant touches it. As long as it's not misaligned, so when you close the throttle it rests on the end of the cable it's ok.
Then see how things are as working through it logically is the best way to solve it.
I'd add to Hoolis' recommendations that the reason the bike can have a change of revs at a traffic light is to do with the clutch switch changing the revs, increasing it a bit to help prevent a stall as the clutch is released. If you're sitting at the lights, just slightly let the clutch out a bit & you'll notice the engine revs increase, maybe only 200rpm or so, but it's there, now if you have aftermarket levers or a dicey clutch switch, it could be playing up.
Check to ensure the clutch switch is engaged when the lever is pulled right in & that the engine revs increase as you slowly / slightly let the clutch out.
If you have this switch bypassed, the bike will run, albeit rough, as it's on a rich starting mixture.
Replace those hoses & check the switches it'll be running fine again in no time. Oh yeah, put that idle adjuster back on & set it too.
Thank you both Hooli and Kiwi for your inputs. (Right before pressing post, I realized we cannot post videos in the thread itself, so feel free to navigate (Google Photos link with the videos) (https://photos.app.goo.gl/apKoezsKQ5HmTcaM8) for the content)
1. Kiwi, my bike doesn't increase RPMs at all when pulling in the clutch. I get that probably the K2 model comes without the so called "clutch assist".
2. Hooli, I am not sure if any of the vacuum hoses are "shot" or any of the PAIR system hoses being "shot". For now, these hoses are not something that I will address, however, after I will send my injectors for cleaning, I think I will also get new O-Rings (E10 ready) and new fuel/vacuum lines (E10 ready). If I will have the patience, I might throw in a fuel filter replacement as well. I see on videos and in the forum, that it is a relatively easy swap. Disassembling the fuel pump must be a much more advanced task.
Let me tell you what I did, I will also try to post videos, so that you have an idea on how I fixed the bike.
So, my lovely girlfriend, came with me to the garage and she helped me set back all the screws/springs that I fugged up...
1. Spring that used to be between the throttle valve and operated the throttle for TBs 1&2 is back in its original place. However, I wasn't able to put the original spring in, it was too hard to squeeze it. Instead, I put in a spring with the exact diameter, alas, less nm of spring rate. It is slightly softer, so I was able to compress it with my fingers and put it in its right place. Seems rigid and that it won't fall (unlike my makeshift alternative that I had there before).
2. Black Knob/Idle Adjuster mechanism is also now back in its place. Again, I couldn't put the same spring back on it, I used a slightly softer one which did the work. Now the idle adjuster knob is well sat in the threads and I have a lot of room to adjust the idle >1100RPM unlike before, where the knob wouldn't turn. I forced it (that dreadful day) and I probably made it slip out of its place.
3. Screw and spring that are responsible for the balancing of TBs 1&2 with 3&4. Sitting back in its rightful place and used it to adjust the TBs. No problems.
Now, as you will see in the videos, the bike, when I am doing extremely small and delicate throttle blips in N or when I rev match from 2nd to 1rd, the engine sounds like a fart, and as if it is chugging. It only happens with very rapid movements of my wrist.
I can only assume that my 2 throttle cable setup must be incorrect.
Despite that, when the bike is perfectly idling at 1100RPM (hot or cold) you can hear tiny pops from the right hand side exhaust pipe. Very small and barely noticeable. Let me know if you can hear them in the video.
I believe that this is happening because my bike is stock ECU and mapping BUT with an aftermarket full Devil system, which probably makes the bike run slightly leanner and since the ECU doesn't have any O2 sensors to TRIM fuel, the bike runs with a slightly higher AFR than it would expect (from stock headers and muffle).
One last noteworthy piece of information (I guess) is that when checking the vacuum reading while loading the bike, was opening the throttle very slowly, I noticed that post 3k~4k RPM, cylinder one would show a slightly lower vacuum comparted with 2/3/4. This is what prompted me to have my injectors cleand, as I mention to my specific reply to Hooli.
Please let me know your thoughts on my own diagnosis on this.
Thanks a bunch for your contributions so far!
I wouldn't bother yourself about the mapping. Early bikes run rich so often are happier with an aftermarket exhaust. My K3 has a full Delkivic system and runs perfectly well on the stock ECU and mapping.
One thing to note using softer springs between the TBs, I put a very soft one in once as it was all I could find. At higher throttle it wasn't strong enough and that TB was more open than the rest, causing interesting things when riding fast. Especially when shutting the throttle and that cylinder stayed open a bit so I was lacking engine braking.
You should see a difference when pulling the clutch in, if you don't then replace the clutch switch. They're cheap and it affects the ignition and fuelling maps so worth doing. My K2 would backfire, cough, bang and drink fuel when the clutch switch stayed on. Fix that before doing anything else or you are probably wasting your time.
Quote from: Hooli on Saturday, 25 April 2026, 02:33 AMI wouldn't bother yourself about the mapping. Early bikes run rich so often are happier with an aftermarket exhaust. My K3 has a full Delkivic system and runs perfectly well on the stock ECU and mapping.
One thing to note using softer springs between the TBs, I put a very soft one in once as it was all I could find. At higher throttle it wasn't strong enough and that TB was more open than the rest, causing interesting things when riding fast. Especially when shutting the throttle and that cylinder stayed open a bit so I was lacking engine braking.
You should see a difference when pulling the clutch in, if you don't then replace the clutch switch. They're cheap and it affects the ignition and fuelling maps so worth doing. My K2 would backfire, cough, bang and drink fuel when the clutch switch stayed on. Fix that before doing anything else or you are probably wasting your time.
Hey Hooli,
Thanks so much for this. I would never think that the clutch switch might be the troublemaker here. I have never tried starting the bike without clutch to see if it is actually always on. lol such a miss...
On the spring, indeed, I will extensively test it, for now it's seems ok to be honest. Even letting go off of the throttle seems smoother than before. maybe the fact that cylinder 1 might show less vacuum than 2/3/4 would be the spring mismatch instead of injector being faulty. Such a good catch!
I'll test and act accordingly.
Sounds like the symptoms you have are the same as mine to be honest. Therefore, I'll definitely try this out. If the clutch switch is faulty, meaning it's always on, the bike should start without touching the lever, right?
One last thing, I guess you recommend an OEM clutch switch right?
Guys...
Are the pictures of said " helping Girlfriend" not loading for you too?
For now i will assume this is an urban myth as there a no picture to proof it
:nyahnyah:
Quote from: imweirdimnotsocial21 on Saturday, 25 April 2026, 02:53 AMHey Hooli,
Thanks so much for this. I would never think that the clutch switch might be the troublemaker here. I have never tried starting the bike without clutch to see if it is actually always on. lol such a miss...
QuoteI've seen the spring fail inside the switch so it doesn't stay off when the lever isn't pulled in, doesn't mean it'll start without pulling the lever though.
As a quick test, start the bike & unplug a wire from the clutch switch before you ride it.
Quote from: imweirdimnotsocial21 on Saturday, 25 April 2026, 02:53 AMOn the spring, indeed, I will extensively test it, for now it's seems ok to be honest. Even letting go off of the throttle seems smoother than before. maybe the fact that cylinder 1 might show less vacuum than 2/3/4 would be the spring mismatch instead of injector being faulty. Such a good catch!
I'll test and act accordingly.
It was a very soft spring I used to cause the issue, out of a ballpoint pen I think & cut down to fit. Just thought I'd point it out as a possible thing.
Quote from: imweirdimnotsocial21 on Saturday, 25 April 2026, 02:53 AMOne last thing, I guess you recommend an OEM clutch switch right?
I use cheap pattern ones, they last years in my experience. In fact I've got one floating around here somewhere as I got it 'just in case' when checking a mate's bike over but she didn't need it.
Good luck with it, sounds like you're getting there.
Quote from: imweirdimnotsocial21 on Saturday, 25 April 2026, 12:43 AMDespite that, when the bike is perfectly idling at 1100RPM (hot or cold) you can hear tiny pops from the right hand side exhaust pipe. Very small and barely noticeable.
have you put new injectors in? I went down that route, the new ones I put in weren't flowing enough fuel and caused that popping and chugging. Original injectors back in and all sweet.
Re vac lines, definitely worth checking, its only cheap auto vac hose and easy to replace. I also did new t pieces in case they had cracks in them.
Clutch switches, cheap oem parts from Webike Japan. Or generic work just as well.
Re the black idle screw, ive found it best to set the base 1100rpm idle using the main adjustment screw, after checking that the throttle cables are all set correctly up at the handlebar. I've hardly ever used the black idle adjuster, only on really hot or cold days to fine tune idle back to 1100rpm (cold air makes it idle higher as its more dense, hot conditions and it drops idle).
Thanks again Hooli/Erik,
Currently bike is tucked in my garage while I enjoy my vacations back in Greece. Will be back on the 7th of May.
1. I've ordered a P quality clutch switch for 10€, I'll fit it as soon as I am back from vacations.
2. No, all is stock on the bike except the aftermarket exhaust system which is a Full Devil system.
I'll keep ya all posted on my extravaganza and issue!
Thanks for the valuable advice! :cheers: :smitten:
Update as of today.
The bike runs fine. I have completed 120km trips in 2 days and I have had no issues, other than intermittent loss of power while starting from the lights, as if the bike loses power for a millisecond and then starts pulling again.. Not everytime, but when it happens, it's kinda scary to be honest.
Additionally:
1. It won't start from the first press of the ignition. It will start on the second attempt.
2. When I press the kill-switch to engage the bike and have it prime the fuel pump and cycle the STVs, I hear a sound that I could best describe like "hard rubber rubbing on a glossy/slippery surface". It does this only when cold and only during the first priming cycle.
I have installed a new P-Quality Clutch Switch. The old one was working, as I tested the bike on the center stand by putting 1st gear and then pulling in the clutch while the wheel was free spining in the air. Yes the revs did increase while pulling and decrease when I left the clutch.
For some reason, this doesn't happen at a traffic stop, when I am waiting for the light to turn green and I have the clutch pulled in while on 1st gear.
Same thing happens with the now new clutch switch.
I have also ordered a used MAP sensor to try to diagnose and hopefully fix the same issues described here (https://gsx1400owners.org/forum/index.php?topic=5477.msg73049#msg73049) as well.
The bike has a really choppy and boggy feeling while no throttle is applied and is simply idling on any gear, as well as, floating 2.5k to 3.3k RPMs, meaning that I have my wrist stable but the REVs are floating slightly and the bike is "bogging".
That said, I expect the MAP sensor, if at fault, to fix SOME ISSUES.
The rest, I believe will be addressed by putting on a new fuel pump (JMP one).
Please let me know your thoughts on this so I can get a step closer to solving my issues! <3
Thanks y'all!
If the bike has been sitting around a while (you say you've been to Greece) how old is the fuel & what did you put in it last? Could just be a fuel issue. Don't use ethanol fuel in them, think the owners manual said you can go to E5 or maybe E10. I'd rather avoid it altogether, in NZ we don't have E5 or E10 so not an issue.
Hey mate, just poured in 19L today, and the bike behaves just like my last reply.
In Poland, we're using E10 fuel (E5 is rather expensive), however, E10 means "up to 10% ethanol", and some tested fuels actually do not have >5% of ethanol in them. I am well aware of the ethanol issue on older bikes, I used to ride a carburatted GSF650 Bandit (worst carburated model ever).
What else might be an issue you reckon?
Dunno, it was just the fuel thought & the fact the the 14 can run rough on E10 -
E10.jpg
Mate, if your changing pump do high pressure filter as well.Busa copy ones fit and are cheap or external filter mod.