Challenging Motor Question....

[Blue Bayou]

I have a strange little thing that happens with my 05 Gen 1 Busa motor. It mostly does it when
it's fully up to temperature. I'll pull up to a light and be sitting there and all of a sudden the
motor will idle up just a little bit (maybe 200 RPM), for just a third of a second or so. Then it won't do it for another few minutes. My 06 never did this, so I don't think it's normal. It's totally unpredictible
as to when it's going to happen. It doesn't really hurt anything and it's not annoying, but
there's gotta be a reason for it. I'm wondering if it's something like a dirty plug connection to
the ECU or maybe a faulty memory spot in the air/fuel map..???
BB

[rubbersidedown]

When did it last get a tune? Plugs,air filter,clean injectors?

[sixpack577]

It's not in the ecu or it's connections.
Clean the fuel system, filter, throttle bodies, injectors.
Sync the throttle bodies and set the idle speed.
Make sure throttle cable is adjusted and routed correctly.
That will most likely fix it.

[sixpack577]

The same bikes, of any kind, and including Busas will dyno different numbers.
And the numbers can vary alot.
Stock and slightly modded, on the same dyno, by skilled operators.
So there is still such a thing as a strong or weak engine from the factory.
The reasoning behind it has always been that a particulary strong stock engine, just happens to have all tolerances in the perfect spot of their quality control assembly range(whatever that may be). Or the not so perfect, but still acceptable range, and they don't run to their fullest potential.
Those things can also cause small hiccups like you mentioned.
With your bike dyno tuned well, even in stock form, you will notice a difference in performance, smoothness.
That funky idle spot would go away too(but the things mentioned the last post will likely fix it anyway). So that is the only real way the ecu stock map could effect the stock engine.
When an ecu goes bad, 99% of the time things go haywire or just completely no longer work.

[shade]

Valves that need to be adjusted can also show these symptoms

[Blackmax]

vacuum leak

[sixpack577]

Valves that need to be adjusted can also show these symptoms

I'de be willing to bet they are all in spec.

[Cantab]

Cant remember if it was my 07 SV Thou or GSX1400 (maybe both) but they would slightly raise RPM when
id just started to let the clutch out from taking off from the lights or a stop sign.
I havnt noticed on the Bus but will take notice next time out.

[Cantab]

The reasoning behind it has always been that a particulary strong stock engine, just happens to have all tolerances in the perfect spot of their quality control assembly range(whatever that may be). Or the not so perfect, but still acceptable range, and they don't run to their fullest potential.

Ive been told this by different mechanics form time to time, also the first year or so of new engines are usually the best/tightest ones as tolerances on tools and dies
arent very worn compared to a current model that maybe 7 or 8 years old, some tools and dies etc could be near the limit but still in spec.

[Blue Bayou]

Ok, thanks guys, you've given me things to check and food for thought..!!
BB