Jerky throttle (busa K0)

[Quart]

So,
lately in the last months I've been having this annoying issue.
The throttle at minimum 5-10% causes the engine to act jerky whenever I don't accelerate with enought decision.
Kinda when I'm running steady for istance at 1,5-4k rpms maintaining a steady speed, the engine will gulp every tot until I don't open the gas.

• Checked the forums, so bought a vacuum sync (carbtune pro), synced the throttle bodies.
• The effect got slightly reduced but still there. Tried to swap exhaust pipes, nothing new.
• Tried to trigger the PC3 more or less for fuel at low/mid rpms, it changes for a while and then back again. With lean mixture will go worse, with rich mixture will go better.
• Checked today the TPS. Shorted into Dealer Mode, the engine when running hot (with fan triggered) has the TPS already in the middle. It may swap to high-check if i accelerate to 2k rpms but on release it goes back to middle check.

Issues and state of the Hayabusa.

• Hayabusa model 2000, 350kph tacho (220mph)
• 91.000 kms
• Exhaust de-kat with cross pipes 4-2-X-2 and Carbon-titanium exhausts
• Pair Removed
• BMC air filter
• PC3 (grossly setted, lacks a decent map).
• NGK CR9E Spark Plugs with 6.000kms
• Has oil leaking from valve seals, eats about 100gr oil every 1.000kms
• The engine accelerates up to rpm limiter without issues
• Inside the combustion chambers there is some mess due to oil burnt
• All exhaust pipes heats themselves altogheter (sparks firing ok I guess).

So what's left to check? Should I recheck the TPS? Should it NOT move from middle check when accelerating the engine to 2k? Is it fine that it swaps to top mark?
Injector to be cleaned? Effect of the dirt combustion chambers due to oil engulfing the sparks?

I've noted that if I roll throttle up in neutral for a while (kinda when you do it for horrays) the annoyance will be reduced for a while.

Any advise will be welcome

 

[WuzzaCBXRider]

You haven’t mentioned adjusting the throttle cables, easily the quickest fix, if nothing else, to eliminate them as a possible cause. With what you have mentioned, the PC3 is suspect. I also didn’t know the 1st Gen Busas had a cat to ‘de-kat’ with an exhaust swap.

 

[Bumblebee]

Were the valve clearances checked lately?

Have you tried to disconnect the PC to see if that helps?

How does the fuel filter look?

 

[Duc96cr]

My ‘06 I felt had a jerky throttle too. PO had installed a device that got allowed full timing advance but in all gears . I removed that, it got somewhat better. Full tune up , cleaned and synchronized throttle bodies, better. Removed the flapper in the air box and it got a lot better. That flapper, due to the fact that it is vacuum operated, delays too much when opening from a stop and causes a little lurch when it suddenly opens and dumps air in just as you’re trying to be delicate with the throttle. Look up the modification, i didn’t invent it. Mine is much better now.

 

[Berlin Germany]

@Quart

for info only - as far as i know a K0 doesn´t exist anywhere

a 2000 has the "Y" as "name" ( the ´99 is the "X")

the "K" is only used at the 2001-2007 / K1 - K7 + at the 2008-2009 / K8-K9

the "L" is used at all 2010-2019 / L0-L9

the "M" is used at all 2020 and younger / later starting with M0 (M zero)

_______________________________________________________________

if not yet available download the entire manual and microfishes (exept the owners manual - no one needs it) from this post .

_______________________________________________________________

to the jerking
spend a "minute" and watch my hp here
at the very last 6 lines at the table

there i listed all currently known 6 possible issues with constant speed jerking (also called "KFR" at my german page)

and for a spatially somewhat closer chance (only over the alps / not over the big pond ) to get info try the german forum at https://www.hayabusaclub.com
there they have a special italian part

good luck

 

[Quart]

Damn, forgot to write it, done that too as first thing before Carbtune

 

[Quart]

Were the valve clearances checked lately?

Have you tried to disconnect the PC to see if that helps?

How does the fuel filter look?

Valve done (chain and so) at 55.000kms.
Without PC3 the problems stands (also gets so lean that engine overheats in traffic)
Fuel filter is unknow. Gotta do it this winter, I mean the whole (external) fuel pump.
So far as pressure the output is OK (from the Pump --> Fuel Rail). Injectors are the guess.

 

[Quart]

Thanks for the page link and info regarding the "K0" XD ye I know about XY but it was a bit odd to write "Busa KY"

Regarding KFR stuff:
1) no front forks are great, redone them 3 years ago they have no play
2) changed the fuel hoses back and on the fuel pump 1 year ago or so with fresh new OEM ones (the one with the bending)
3) throttle cables got their play
4) Could be an idea, the gear sensor. Could test it disabling the running map (using the neutral map shorting the switch); if the problem persists means that's not that.
5) pump itself? Maybe but I don't think so, the problem is so randaged by the engine rpms and air/fuel ratio. But the unconstant pressure may be caused by clogged filters maybe on the injectors (or the pump giving bad costant pressure under light load).
6) stator sensor? Didn't consider it, may be a good idea to check it out.

Thanks for all the tips Whenever I'll have time (and money) will try to sort it out with your hints
For the immediate future first gotta service oil (and also will swap spark plugs, let's see how will go back with iridium ones).

 

[sixpack577]

I would get it dyno-tuned
The base map could definately be the problem.
Do the airbox flapper mod mentioned above if you have not already.
Clean the injectors and double check that the fuel pump is functioning correctly.
New and low-use parts do fail, and the external pumps are known for issues.
Does the bike have a TRE on it?
That can cause your issue as well.