zxr750 mechanical noise at idle??

T) · Post by T) » Mon Jan 29, 2007 11:11 am

hi guys,

bought a zxr750 l1 a few months ago with a motor problem. was quite ridable, but had a bad blow-by problem due to previous bad cylinder repair. (cracked ring i believe)
motor was noisy at idle as well, so when i fixed the cylinders i rebuilt the bottom end as well.

all bearing clearances were spot on as per manual & were replaced with standard sized parts.

got the thing running again yesterday with the rebuilt motor (yay) no blow-by now (which is good) but same mechanical noise exists at idle.

spoke to a bike mechanic i know & he did mention they have noisy valve trains. all valve clearances are spot on.

is this "normal" on a zxr750? (or do i need to elaborate more on the type of noise?)
noise sounds like bad valve clearances or maybe even bearing clearnaces (bottom end knock). seems to go away off idle. (or is drowned out by exhaust - one or the other) will have to take it for a ride to see if the noise exists anywhere else in the rev range (or other problems exist)

T

Zteven · Post by **Zteven** » Mon Jan 29, 2007 1:14 pm

Last zxr750 I had was the '92 model(from new) & it had a noisy valve train which made more noise on it's side stand than straight up, sounds like your gunna have to get use to it.

Smitty · Post by **Smitty** » Mon Jan 29, 2007 5:58 pm

Toby
the Kwaka 7 engines isn't what you would call quiet

at idle, you will have zzzzing or zmmming noises from the
camchain/tensioner plus a tapping noises from the
valve train is also normal

the valve noises should quieten as revs go up
but the cam chain will still be heard

It should be simple to distinguish between topend
(valve/cam noises) and bottom end noises
the old screwdriver test held to the ear can be used

If you have rebuilt the bottom and all clearances are ok
you should hear nothing but the primary chain

btw
don't be tempted to close the clearances up, up top
to shut it up....stuffs valves and the seats real quick

hth

T) · Post by T) » Mon Jan 29, 2007 8:36 pm

hi ian,

have not run the bike for very long so far, but does not appear to be anything majorly wrong with the motor (yet)

seems to settle down when the revs come up but really have not ridden it due to no bodywork, front brakes need to be bled up, tyre pressures checked & the throttle cable was sticking (throttle cable now fixed so we are progressing:)
no reg does not help either but we have an lmct at work so that is easily fixed

hoping to get it registered next week assuming it does not blow up or try to kill me this week

T