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hello all,

this is my first post so if this has been said before, my apologies.

i have a zxr400 l1 and im having trouble with the carbs. i think it would be best if i explain in full so here goes...

it normally started without any choke and always smelled a little rich so i guess it must have been?

then the other day when i came back from a trip out i let it idle for a couple of mins, and it started to run a little rough, so i gave it a few revs but instead of the normal pick up it just bogged and stalled and was hesistant for a few seconds and then picked up, but still poorly. took it out again and gave it a good reving and then it was fine again at idle, for a couple of mins at least, when it did it again.

so i investigated and found upon taking it apart that the fuel tap doesnt really work, it flows a little in the off position; also that the float bowls were brimmed.

so, tank off, fuel line off the carb, fuel pump unplugged, started bike and ran for 10 mins perfectly ay idle and revved no probs - on the fuel that was in the carbs.

this led me to beleive the float valves were letting fuel by and overfilling the float bowls, and as there was no fuel supply filling the bowls the problem had gone, not really a long term soloution though!

took the carbs off, checked the floats, floating nicely and freely, blew though the fuel inlet and no air is blowing out when the valves are closed, so no obvious leaks at the float valves.

checked and cleaned up the rest of the carbs and they seem to be in pretty gd condition.

the mixture screws were 2 turns out, so i turned them in by half a turn.

put em back on the bike and problem seemed to have gone untill about 15 mins later when mr problem came back, it cut out and refused to start, so i drained some fuel from the bowls and it started, then cut out again after a few mins.

spark plugs are black.

is there any solution apart from dont let the engine idle and keep it high revving?

your help and patience is appreciated

Andy.

could it be the fuel pump over pumping fuel?

is there supposed to be a flow restrictor on the tap to stop excess amounts of fuel being sucked in and pushing against the float valves?

please help its so annoying, the bike is unridable!

It would seem like your bike is flooding or overfilling the carbs............

Iknow that this problems can occur if the o rings which fit in behing the float valve seats are dozed and passing fuel

cargo wrote:It would seem like your bike is flooding or overfilling the carbs............

Iknow that this problems can occur if the o rings which fit in behing the float valve seats are dozed and passing fuel

+1 had it on 2 zxr's now.

thanks for ur replys!

how do i get to these rubbers? with the float bowls off, i see a jet? in the middle of each 1 and something either side of them im not sure what, i learn by exploring though! where do i got from there?

ive had the carbs off and cleaned them up, taken the valves off the floats and they seem to be ok, when the carbs are upside down, and the float valvess are out, i can blow air into the fuel inlet and it will blow into the float bowls, but when i put the valves back in with the floats holding them closed by gravity, i cant blow thru, is that a valid test to prove they arent passing by that much? or is the fuel pump at a lot higher pressure than my breath, im guessing so.


is there any chance it could be the fuel pump gone bust and pumping too hard? or the fact the filter isnt providing any resistance to the pumping of fuel?

thanks again

andy

remove the floats and float valves then pull out the brass collars that the float valves sit in .. they have an o-ring round them to seal against the carb body, these perish. Also check the tapered tips of the float valves for any grooves (wear)

blowing air through isnt the same as fuel.

doubt its the pump.

pay attention to the float heights too as set too high will also cause these symptoms without any wear present.

procedures are in the H model manual (L is a supplement and has little detail)

ok ill give that a try, thanks!