r/zx6r

it’s coming from my spark plugs but i checked them all and they’re all snug

Anybody know where to get new fairings? or is it just worth buying OEM?

Got used as sidewalk chalk today and need new panels

I’ve been going in circles with mechanics for months and nobody can properly diagnose this. Laying out everything I know in detail hoping someone here has dealt with this before.

The Bike
2016 Kawasaki ZX6R 636, 19,000km. Black and green. Previous owner removed the catalytic converter and fitted an SC Project slip-on exhaust with stock headers. No retune was done after this modification.

Pre-existing Issues When I Bought It
The bike has never hit the rev limiter since I owned it. It just hits a wall around 10-11k RPM — not a hard cut, not a limiter, just stops pulling. Above that it’s like riding into a wall.
It also always ran extremely rich. Standing behind the bike at idle my eyes would burn and the fuel smell was overwhelming. Fuel consumption was consistently 13-15L per 100km which is terrible for a 636.
I also had a DB killer fitted on the SC Project for a while before removing it. This caused significant carbon buildup throughout.

What’s Been Done
After a lowside crash I took the bike to a shop for a full restoration. Here’s everything that was done across two visits:
Visit 1 — New forks, fork seals, fork oil, front axle, both tires, brake pads, full fairings reinstall, throttle body sync, radiator flush with coolant change, full detail. Bill was around AED 12,400.
Simultaneously I sent the ECU to Moore Mafia for a tune. The tune instructions specifically say to remove the O2 sensor. The O2 sensor is still plugged in. I only realised this recently.
Visit 2 — Injector cleaning, spark plugs replaced, secondary air reed valves decarbonized, ABS sensor diagnosed as faulty. Bill was around AED 2,271. Power issue still not fixed after this visit.

Current Symptoms
This is the important part:
In neutral — bike revs freely and cleanly all the way to 11-12k RPM. Zero issues.
In gear under load — hits a wall around 8-10k, RPM won’t climb, and under full throttle the bike actually loses speed rather than accelerating.
Heavy carbon buildup throughout from the DB killer period and rich running history.
On startup when the key is turned to ON the subthrottle actuator makes a stuttering sound during its calibration cycle instead of a clean smooth whirr. This is a known symptom on 636s.
O2 sensor still plugged in despite the tune being designed to run without it.
ABS warning lights and KTRC issues were also present but traced to a wheel speed sensor disturbed during the fork and axle work — new OEM sensor on order and this appears to be a separate issue.

My Current Theories
Three things that I think are working together:
O2 sensor plugged in while running a tune designed for open loop — sensor is fighting the tune’s fuel maps causing rich running, erratic fueling and inconsistent power delivery

Subthrottle actuator failing — the stuttering calibration sound on startup is suspicious. This is a documented failure point on 636s and would explain a specific RPM wall under load. In neutral the engine doesn’t need full airflow so the stuck valves don’t matter as much

Exhaust backpressure from carbon buildup — DB killer used for extended period, lots of rich running, potentially heavily carboned exhaust internally causing restriction under sustained full load

What I Haven’t Tried Yet
Unplugging the O2 sensor — doing this immediately

Disconnecting the subthrottle actuator connector to test whether the valves staying closed is causing the RPM wall

Physical inspection inside the exhaust for carbon buildup

My Questions
Can a plugged in O2 sensor fighting an open loop tune cause power loss and rich running this severe?

Has anyone on a 2013-2016 636 confirmed subthrottle actuator failure — is the stuttering startup sound a definitive sign? Did disconnecting it fix your RPM wall?

Has anyone experienced exhaust carbon buildup severe enough to cause a specific RPM ceiling under load but not in neutral?

Given that the bike revs fine in neutral but hits a wall in gear — does this point clearly to one specific cause in your experience?

Anything else I’m missing given this history?

Bike is in Dubai so options are limited. Already spent significant money at shops that keep treating symptoms without finding the root cause. Trying to properly diagnose before spending more.

TL;DR — 2016 636 never hits rev limiter, walls at 10k under load but revs fine in neutral, rich running history, O2 sensor plugged in despite tune requiring removal, stuttering subthrottle actuator on startup, heavy carbon buildup history. Three shops haven’t found the cause. Help.

Post this in r/Kawasaki, r/motorcycles and r/motorcyclemechanics for best coverage.

After owning this amazing bike for 6 months i realized theres nothing on the marker that gives you such a riders feel. I’ve owed gsxr 750, cbr 600 and even an r6. And for a modern bike of recent years this bike has everything from the aggressive feel high rps and nimble feeling in corners to even the comfortability to commute with in low power modes. Theres nothing i would recommend more then this

Seems like it’s too good deal

What yall think?

This bike is straight up therapy🫶🏽

Didn’t even plan to buy the bike today, I was looking to trade in my 2025 KLX300SM that I got 4 months ago but they only wanted to give me $3,500 for it which would be me taking a $2,500 loss on it in 4 months. They asked if I wanted to look at financing without the trade in and next thing I know I’m getting the keys. Have ridden a few dirtbikes but this will be my first street bike. 2026 ZX6R ABS, $12,000 otd. Now I have two bikes lol. At least it will keep my mind busy. Any tips and pointers welcome, thanks! I will take it slow while learning

Hi i am new. I want to install a slip on exhaust and i understand that there are 2 sizing for the mid pipe which are 51mm and 60mm. Which size should i get? What is the original size from factory? Is there big performance difference between one over another? Thank you so much.

Wanted to show off some of the work I’ve done to repair and transform these beat up track fairings I bought for my 2005 zx6r. Was a lot more work than I initially thought but I’m pleased with the results. Lots of fiberglass repair, bondo, and sanding. Rattle can sunburst yellow with an automotive clear mixed with a gold metallic pigment. And also did some forged carbon skinned the fiberglass fairing. Almost ready to take to the track and let er rip.

I recently crashed my 636 and have no recollection of the accident so I have to rely on the police report to fill the blanks. The report states that I lost control and was coming too fast in a corner, but all that doesn’t make sense!! A car saw me crash said it was following me at 90 in a 90 zone(km/h) and I juste fell on the side before the curve juste like if my wheels locked. I barely survived the crash the doctor says I’m a miracle I’m recovering extremely quickly and all is fine for now. So when I was able to buy a new phone I started looking for the cause and the second recall popped up! I was never notified in anyway about a second recall and wanna know ur opinion. What should I do let things go as they are insurance are covering everything and all is fine or notify them that I had a mechanical issue and they should check the bike.

Edited: sooooo good new bad new
I contacted the mechanic who had my bike he said it was sent yesterday at a nearby auction and he advised me to shut my mouth on the recall thing because they will chek the bike talk with kawa blablabla and won’t pay me until case is solved. That can take a WHILE. So I will let things go cash the money get better and go on with my life with the hole in my story
Thanks to all of u for ur support and good advice i hope u all have good ride and never have to go through what i am be safe out there!

You guys think it's worth rebuilding my wrecked zx6r? The front fork won't turn all the way to the right because it's blocked by the headers

I am currently rebuilding my forks and I ‘hammered’ the oil seals out. It was kinda stuck so I had to use a heat gun to loosen the oil seal/heat the forks. Upon removal I noticed that the washer under the oil seal is mushroomed/cupped. It looks to be symmetrical. Is this normal or should i replace it? If normal, what side should be up?

I have zx6r 2002.

As the title says, anybody using one? My fork stem mount just came in from them and somehow the mounting stem is too big for the nut hole. Anybody using the fork stem mount and get it mounted without issue?

My only thought is to use a long magnet to feed it up through the bottom of the triple tree and mount it that way.

Having bogging issues at high rpms, bike has no go up there, changed air filter and plugs, fuel pump was my next step. Is this some kind of sealant that was put in? Anyway to clean/remove it?