91 ZXR750 carb problem?

[Tack]

I've got a problem with my 1991 ZXR750J track bike. It's been about 6 months since I started it last and because I want to do a few more track days I thought I'd better get it going etc.

Put new plugs in..changed the fuel filter...ran the fuel pump to get fuel up into the bowls...started it up...runs on choke, in fact revs like crazy on the choke..crisp clean...but not on throttle...won't idle..dies when any throttle is applied....let it warm up..still wouldn't idle or run on throttle!

Took the carbies off...had a look in the fuel bowls..all clean...one needle (needle and seat) seemed to be a bit sticky but that freed up....floats seemed ok, pivited ok not sticking..no crude or residue anywhere..all the jets looked ok?

Put the carbies back on...same thing...won't idle...dies when any throttle is applied?? So I dunno...if it were electrical I would expect that it wouldn't rev like it does...runs fine with choke held on...runs rich though...makes the eyes water..........I can only think it's the carbies but dunno what it might be...it was running fine last time I ran it so .....any ideas!

Thanks

[Rusty]

Clean out the jets and emulsion tubes - they're clogged.

[timmyrocks]

jets mate, either that or your passages are blocked,
to narrow down remove your airbox, start the bike run on choke and twist throttle to see whats happening you should see a mist of fuel on a big throttle opening,,,, to cancel out electrics turn choke off and get some "start ya bastard" (aerostart) and crank over and run it on the spray for a few seconds.

if you reckon your jets are clear then id strip the carbs and saok them in carby cleaner and get some compressed air through your idle passages, and air passages and such.

hope that helps mate, cheers Tim


oh and just to be shore make shore air filters in good nick

[Kwak addict]

You didn't leave a bunch of rags stuffed in the air intakes after you last used it did you?

[Tack]

You didn't leave a bunch of rags stuffed in the air intakes after you last used it did you?

LOL..No..but thanks.


The problems seems to be with the float needle and/or floats. Fuel is draining past the needle and seat and into the intake ports and out the float bowl overflow.


Don't really understand why though. Had the carbies off three or four times...cleaned everything...wasn't any residue or junk anyway....checked the floats...they move fine...no sticking..proper movement....needles and seats were new when Dyno was done and carbs were rebuilt 2 years ago....needles have no wear marks where they seat, they slide in and out fine

The fuel is actually draining past the float needle from the tank without the engine running!

Have to drop the oil now and put new oil in but really at a loss as to why the floats are behaving this way.