Performance mystery

Hi,
I've just finished doing my first major service the first test ride was a
disaster. The problem has gone away but I'm very curious what it may have
been. The bike is a 99 ZX-6R with 60,000 km.

This is what I did to the engine:
Valve clearance (all good).
New plugs. New oil / filter.
Carb balance.
Clean air filter.

This is how it went:
Bike idles great.
Revving on the spot the revs come down very slowly.
Riding through congested traffic bike seems a bit down on power.
Traffic opens up onto freeway, there is no power above 4/5krpm.
There is not enough power to get over 60 kph!
I putt along emergency lane to the next exit and hobble back home at about
30-40 kph rolling where possible.

Once home I discover:
Fresh air exhaust thingies not attached, only difference is they'd suck from
behind the fairing instead of in front.
Spark plugs greyish white (indicates running lean?)
I found no other disconnected or kinked tubes or any loose connections.

I reassemble the bike and try again. Everything is back to normal...
All's well that ends well, but I'm curious as to what the hell I could've
done wrong?
The plugs obviously still work but should they really be replaced after
going a bit too hot?

Cheers,
Duncan.

 

Was everything attached to the airbox that was sposed to be?

Daron

 

Fresh air_exhaust_thingies? Wtf?

OK, what runs to the front of the fairing?
1. The main ram-air ducts.
2. The carbie float bowl pressure-equalisation hoses. These start with small
circular inlets inside each ram-air duct, visible just behind the protective
mesh at the intakes. They then exit through small plates that bolt onto the
back of the inlet section of the ram-air ducts, where the back wall of each
inlet duct still faces ~forwards. A short hose connects each of those to a
Y-piece which, in turn, connects to a small black cylindrical chamber-type
thing. A single, longer hose then runs from the back of the cylindrical
thing, through one of the holes in the frame next to the steering head, and
plugs into a rail that connects all four carbs. This keeps the air pressure
in the float bowls equal to that in the airbox, allowing the air being
pulled through the carbs to suck the correct amount of fuel up through the
jets. If the pressure in the float bowls is lower than in the airbox, then
the float bowls won't want to give up fuel as easily; there won't be enough
air pushing down on top of the fuel in the bowl to allow it easy passage out
(think of how reluctant oil can be to drain unless you undo the filler cap
up on the clutch cover). Consequently, the bike is likely to run lean.

When I pull my bike apart, I disconnect the pressure-equalisation hose at
the cylindrical thing to allow me to take the top fairing off (which needs
to go to allow the rad to swing down to, in turn, allow access to the front
of the head and the exhaust side of the valvetrain residing within, etc.).
If this is what you've done, and then didn't reconnect that hose before
taking the bike for a ride, it's concievable that the pressure differential
was causing the bike to run lean as outlined above. The difference would
occur because the airbox would still be supplied with air being actively
scooped up by the air intakes out the front and rammed in at some speed
(which increases pressure above the static value) while the float bowls
would be breathing into quiescent air behind the fairing. It's possible that
the air pressure in the airbox would rise enough above what the float bowls
could manage for it to become a problem... erm, I think.

Wondering how far off I am.

 

Better split the cases just in case

 

On Wed, 24 Dec 2003 16:53:37 +1100, "Intact Kneeslider"

snip some...

And this from the man who is asking about a carby leak on the L300 van
;PP

Johno
PS. did you solve the problem?
PPS. in case it's still harsh week - get fucked
oh, have a great day tomorrow

 

Johno

Hey Johno, you cruel cruel bastard. Have a good one with jac and the lads
tomorrow. Don't let them let you get silly, and if you do. STAY THE ****
OFFLINE



beer mate?

 

Hey shithead
compliments of the season to you and yours

 

Back at ya Nick

 

Merry Christmas Duncan,
Cant answer all your questions, but the hi revs at idle bit, reminded me of
when my then 1994 ZX9R had its 10 000Km service, the bike was coming back to
idle slowly, and I think it was hi, but not sure now. It went away after
500Km, and and I sold it not long after.
I later read in an American mag. in which somebody had the same problem
after a major service, and the spanner guru, advised that Kawa. motors
should always have the valves set to the high end of the setting tolerance,
not the bottom end as most people would think correct. Apparently it upsets
the breathing of the carbies, and changes the mixture and causes the idle
problem (and spark plug colour?).
Can't remember more than that.
Rob.

 

I'm pretty sure the answer is 2. I made a mistake thinking that those tubes
were connected to the vents with the reed valves that inject air into the
exhuast to burn unburnt fuel.
To be honest I'm still getting my head around what each tube and valve does.
On my subsequent rebuild I went through the service manual checking for what
should pass air and what shouldn't and in which direction.
What you say makes sense, if it's true then those air lines are pretty
bloody sensitive things. It'll be easy to disconnect them to prove the
theory.

 

Thanks Steve, same to you lot in tassie - even that coney and KevGl
fella and all of your cussins twice removed.... have a bloody great
day

Johno
ta for the beer

 

Cheers Johno

and everybloddy else too!

Kevin Gleeson
Imagine It
West Hobart
Tasmania Australia
www.imagine-it.com.au

 

Where do you keep yer blow up doll?

Hammo