Starts up but wont rev?

[ianbhp]

Hey
Just bought a zxr 400 yesterday a friend of mine viewed it with me, he drove it burt didnt get to give it as good run cos of traffic, so he turned into an estate and it cut out, started up again but wouldnt rev up, you would have to hold the trottle fully open for it to idle, Bought it anyway for the right money cause of this, when i got it home on in a trailer( four hour journey, she fired up and ran grand, a bit spluttery down in the revs @ times when moving, but friend drove it back the road and said she was fine and quick, few mins after he returned it wouldnt take the revs again same as b4 strat up fine but have to trottle fully ope in order to tick over , and i started it later on last night and it was fine, reving grand, bit slow on response when driving it but that was on low rev in a yard.

any ideas on this lads & ladies any help greatly appricated first bike and would love to have it running right and get myself on the road as soon as possible

Thanks

[zimm]

so its ..

fine from cold ... but if its been run for a bit then left for a bit its a bugger to start, only catches on one or two cylinders, wont idle etc .

come back to it next day and its the same story repeated ?

my guess : valve clearances have closed up. Once its warm the valves are being held open, so there's no compression.

[ianbhp]

Thanks!
what would be the easiest way of checking this? compression test or dismanteling and checking valve clearences?
Do you know ahat they should be?

[zimm]

If you know what you're doing then check the clearances and swap some shims about, grab the H model manual from the main site (the L manual is a supplement and doesnt describe the process in as much detail)

clearance range is

inlet 0.12-0.17mm
exhaust 0.18-0.21mm

IIRC

aim for middle of the range.. maybe slightly loose.. 0.15mm inlet, 0.20mm exhaust

its a fiddle, but no worse than other bikes infact easier than some as the cams dont need to come out to swap shims

tank off
airbox off
carbs off
plug caps/coils off
cam cover off
furtle about with a feeler guage
re-shim as necessary
re-assemble

done.

[lewisdale]

my old h1 used to do exact the same thing, only when hot, i never found or fixed the problem however i did find it only did it if you gave it throttle trying to start it, if u just let the engine keep spinning over on the starter it will eventually fire up and be fine again, i know obviously this might not be much help as yout want to cure the problem, but it saves you sitting on the roadside for a hour if you get stuck which i did a few times till i got the nack lol

[ianbhp]

Thanks for the advive will attack it over the weekend, ill getsome one with a bit more bike experence to give me a hand checking the valves, going to change the fuel filter anyway looks a bit old too.
I ll let ye know how i get on, and any other words of wisdon will be appricated if ye think of anything else