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2014-09-01 KrZy8 Hard Starting, Rough Running



Documenting this after the event, so timeline might be skewed. But KrZy8 started showing weird symptoms. Had to adjust idle up. Never had to do that before. Then 3 or so weeks later, had to adjust up again. MPG down to high 20's mid 30's. Then she got hard starting, running real rough at startup. Better when warm but not right.

With heavy OT due to 1R19, took her to Ivan at Hidden Power Cycle Clinic to see what's up.

Here's what's gone down so far..

  1. #2 Injector replaced. When Ivan poured a little raw gas into cyl 2's vacuum port, she picked right up and smoothed out.
    1. New injector didn't fix it. No joy.
  2. Spark plugs replaced. No joy
  3. Coils and caps replaced. No joy

Other weird shit -

  1. Ivan has a stand-alone gas tank with onboard pressure regulator. When he cranks the pressure up from 47 psi (oem spec) to about 60 psi, the rpm's pick up and she smooths out. But I would expect that... more pressure = more flow for same pulse duration.
  2. Once, for whatever reason, she fired right up and ran perfect. Even for several starts. Just like nothing was wrong. Then, after siting for a day, back to bad behaviors.

So then, what to do? Order parts. Parts ordered:

  1. ECU - used
  2. Complete throttle body assembly including injectors, TPS, and bodies - used
  3. Throttle body wiring sub-harness - used
  4. O2 sensor - used

Observations -

  1. Won't go into CO mode, diagnostic.. Barbarian mod has been done in 2006 but.. did that harness get replaced?
  2. Dribbling fuel into vacuum port improved running
  3. Increasing fuel pressure to rail seems to improve running (but wouldn't that be expected?)
  4. Plugs running sooty rich all 4
  5. All 4 cylinders running poorly

Attack Plan

  1. Check ECU connector for loose wires, deformed pins
  2. Check ECU connector to see if Barbarian mod has been done
  3. Check TB wiring sub-harness for loose wires, pins, etc
  4. Substitute, in this order, these parts
    • O2 sensor
    • ECU
    • TB sub harness
    • Throttle body

Stopped by Hidden Power Cycle Clinic today and we swapped out:

  1. ECU
  2. Pressure sensor on fuel rail
  3. Fuel injector sub-harness

No happiness to be found. Starts hard and runs rough, getting better as it warms up... almost to normal.


Edit - 

  • also disconnected o2 sensor. No difference or error code either.
  • discovered that the Barbarian mod had not been re-done after warranty work. Did the mod and now Co shows in the Diag mode.

Next step is to check cam timing and valve clearances, just to be sure.. then replace the entire throttle body assembly.


Ivan called and said KrZy8 has been running GREAT since replacing the throttle bodies with ones I recently purchased from eBay for 80 USD. The new TB's replace the fuel rail, 4 injectors,  TPS, manifold pressure sensor and one widget that looks like a regulator but I'm not sure.

Ivan says she fired up immediately upon install is sounds really happy. On cold start this AM, she's a tiger ready to roar.

I'm to see Ivan tomorrow early to verify cruise control is as it should be then he'll button her up.

Oh, the valves were perfect. All in spec.

..fingers crossed!

Stopped by this morning.. KrZy8 is B A C K!

Easy starting, fast throttle response, smooooth....


Will examine throttle bodies over Christmas holiday.

$1,067 later, KrZy8 is home and roaring like a pissed off tiger. Bad throttle body on the hot air circuit somewhere. Dissection to follow. All parts currently still at Hidden Power Cycle Clinic. Felt so good to be back on this bike..

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