Carbs/Idle problem

[Dave_ZXR]

Hello all,

recently bought a zxr 400l that has been sitting for a few months.

was having serious problems with start up.

engine would run on choke but die if I touched the throttle.

Balanced carbs while still on choke in desperation (about 2k revs)

removed carbs had a look at floats, seem ok, no visable gunk.

removed needles and cleaned some greenie brown hard crap off them and refitted.

Now starts better, can use throttle to start which is a first.

Still having problems with idle, wont stay running off the choke.

Im aware of the 3 screws for balancing the carbs but is there anything I can do for the idle?

do these screws also control mixture? if so how do I know if its right?

or is there and 02 screw perhaps?

also found that screw on the otherside for mabey throttle position? (with the long black cable attached)

Really fustrating day with very little results!

All help welcomed
Thanks

Dave

[Davw]

When you cleaned the needles did you check that there is no crud in the main jets? If there was on the needles then there is probably deposits on/ in the main jets. My suggestion would be to fully clean the carbs (if you havent already done so), check the float height (there are instructions eleswhere on the site for that), check/ clean the air filter.

The black "knurled" adjuster on the RHS of the choke body adjusts the idle speed - in effect by opening the throttle slightly

There is no "mixture" adjustment - the original settings (main jet) should provide good mixture for road use however checking the plugs after a few hunderd miles will give you a clue if you are runnign rich etc. If you are racing then the only effective way to sort the mixture (bearing in mind that the air filter has gone, the main jets have increased in size etc) is on a dyno.

[RedexRobB]

as davew said, get the carbs apart and thoroughly clean them. Soaking the jets in carb cleaner overnight and then blasting with air should clear them. Check the cross drilled holes on the jet holders are clear too. That with a re-balance and they should be pretty well sorted

[Dave_ZXR]

Thanks for the advice.

Tomorrow I hope to at least have her running!

Any ideas on how much adjustment to give those 3 screws?
I mean is it like turn them all the way shut and wind out twice or should I work from where I have
Them and try to bring the carbs up a bit?

Thanks again.

[RedexRobB]

If you wanna get the mixture perfect a colourtune kit will do it, it can be manually done by turning them out till it bogs the engine (or it starts to rev i forget which) but is a rough way of doing it.

[Dave_ZXR]

So after another days hard graft, I'm left with cut fingers knuckles and the rest...

RIght here goes,

removed carbs for the third time clean out jets with carb cleaner and air line crom compresser
also repeated with needles
measured floats to be a little over 10mm which the manual says is within limits
refitted
fired her up to be greeted with floods and floods of petrol pouring from the overflow pipes.
removed carbs again
check floats and needles make sure i've put everything back correctly
refitted
starts but strong smell of petrol cant work out where
find leak
its being pushed out the headers!
clouds of smoke from exhaust and also some exhaust popping
remove carbs
more checks
refit
clean all the crap off spark plugs
now starts and idles but I think i've managed to get some petrol in the sump as the plug has began to leak.
also still giving out petrol from the overflows and bellows of white smoke.


to be honest i am at my wits end, I dont know if the bike is worth enough to bother sticking it in a garage.


any ideas are welcomed

thanks
Dave

[RedexRobB]

Rather strange! Did you take out the float needle seats? The fact they are overflowing suggests to me that the float needles/seats are either worn (but wasnt overflowing before) or there crap in there, still.

Alternatively, you could buy another set of working carbs from our resident ZXR breaker falloffslowly rather than sticking it in a garage.

where abouts are you dave?

[Dave_ZXR]

thanks for the reply.

The bike currently lives in hillingdon (mates garage) west london

not sure on the price of new carbs or even if I need to.

I've done something to these ones I just cant work out what.

I was hoping you guys might have a resident carb "guru"

I've checked the needles as much as I can they look ok and seem to be seated correctly.
Could it be the springs that hold them down are gone? Although these seem ok too.

I'm thinking I might bite the bullet and stick it in a local garage for a "bend over please sir" quote.

thanks again

[Davw]

Must be a problem with the float valves/ seats for petrol to be overflowing-although difficult to say. Seems like there are a number of options:-

1) Buy a set of working carbs ("Fallsoffslowly" is bound to have a set and wont sell crap) and sell yours on fleebay (nett cost - around £30 max)

2) Continue to work with these carbs - cost undefinable and you may not solve problem

3) Send carbs off to specialist (NRP would do a full refurb - not sure of cost but they would give you a quote beforehand)

4) Put into garage - probably the worst option unless they really know what they are doing it is likley that they will spend a fair amount of time trying to work out what is wrong - time that they will charge at £40plus/hr

I would go with option 1 if possible

[Dave_ZXR]

thanks for all the help guys,

Im thinking about doing a carb re-build myself, I figure its a learning experience and if it all goes wrong I'll pick up some second hand ones.

I'm gonna call NRP for a quote on a kit and for them to re-build, will post my findings to help others.

[zimm]

my guess is the needle valve seat o-rings causing the flooding

and blocked pilot jets screwing up the idle