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Discussion Starter #1

In the video, I have tippexed the throttle so you can see that my throttle control is slight and solid.
It does this on the road too, If needs be I can upload footage of it climbing from 24mph to 35mph on a dead level road in gear 2 with 1% throttle twist.

For the whole 6 months I have had her I have a really bad problem with the throttle. So basically in all gears.... If I apply a very slight throttle, the RPM will climb on it’s own and never find a stable rpm. It’ll pop and crackle and hover around allot.
It’s really apparent when in slow traffic doing 20 mph or so.... With only the slightest possible throttle open, the bike will slowly over the space of a few seconds, climb from about 3000 to somewhere around 7000 rpm.

Which in real time terms, means that unless I let off of the throttle, pull in the clutch or apply braking pressure... with a slither of throttle open, the bike will start to try and rear end the car in front of me :L
It’s a horrible feeling.

It can go from 24 mph to 35 mph on it's own with no throttle change. NOT VERY SAFE!


I have been slowly working my way through the Chinese, Taiwanese & Korean 125cc Motorcycles (2003-2015) Haynes Manual
Haynes Part #MOL4871 Maintenance list.
I am running out of things I can blame this on at this point
It’s such an obvious and intolerable problem. But yet I am running out of tricks.

I guess that’s both a good thing and a bad thing.
Because my list of probable causes is now very slim indeed.
Here’s a current list of the solutions I have tried.


  • We replaced the Lambda sensor, so it's not that.
  • The valves are perfectly in spec 0.15 out -/- 0.10 in.
  • I've given the drive chain the proper tension.
  • The throttle cable is set correctly with about 3-5mm of free play and no snagging. (all the way through the steering range is tested)
  • The clutch cable is set correctly with 10-25mm free-play (I have mine at about 11mm)
  • The air filter is clean and the sponge filament is basted but not dripping in engine oil as per the manufacturers maintenance guide.
  • The wiring is clean and functioning, no warning lights. (I solved the low voltage warning, there was a lose wire that had sheered off.)
  • The spark plug is new, we replaced that.
  • The oil strainer had some plastic debris on it but is clean now.
  • The cam chain tension and timing is spot on.
  • The rocker arms and valve heads are in immaculate condition.
  • The cam chain looks as good as new.
  • The oil is clean and the right level.
  • The throttle returns to fully closed with no problem.
  • I fitted a new clutch lever and cable with grease.
  • The engine Idles absolutely spot on at 1.6k with no fluctuations or miss-fires.
  • The Bike starts first time every time
  • The battery holds charge and delivers the correct power with no low voltage problems.
  • The transmission is working smoothly and without faults. (It looks in damn good condition too when I had a peak earlier this week)
  • The Fuel filter is clean and the pipes and feeds are ship shape with no kinks.
  • The clutch pads themselves are absolutely fine, In fact they look way more pristine than I thought they would.
  • I cleaned both front and rear calipers, brake pistons and all thoroughly with acetone then lubed the pistons with brake fluid.
  • The front pads needed replacing so I got those in, the rear pads where fine .
  • I have bled and replaced the brake fluid in both front and rear master cylinders.
  • No pulsing or friction on the brakes.
  • I have replaced the front brake disk due to slight warping.
  • I have thoroughly inspected all seals and gaskets on the engine case and I see no oil leaks what so ever.
  • I have double checked all of the wiring as per the diagram in the Haynes manual.
  • All electrical systems function as they should including the Fuel gauge.
  • I replaced the speedo because of that casing damage that was there when I bought the bike.
  • The suspension is damped correctly and feels spot on.
  • It runs at high load and Rpm with no issue.
  • The fuses are all intact and working.
  • The ECU is functioning, thought I don’t know to what level of accuracy.

My list of things I think it could be are as follows;

  1. A Vacuum issue with the air intake manifold, maybe a small leak in the intake system?
  2. A faulty TPS? (I think this is the most likely, but experts might not share that opinion?)
  3. Maybe an incorrect programming on the ECU?
  4. The Bluetooth transmitter for the ECU?
  5. Maybe dirty fuel tank D: I( mean I am scraping the bottom of the barrel with that one)
It’s behaving like I have the throttle open about 80% or so when in actuality,
my throttle is open so slightly, that if I even slip one mm forward the throttle cable is out of range and the throttle is completely released.

It’s just such a shame that it is still so disobedient and dangerous at low speeds and RPM,
Because when it’s not, it rides absolutely brilliantly.
 
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