Carb diaphragms vibrating

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krystian579
Posts: 2
Joined: Mon May 29, 2017 3:26 pm
My Bike: ZXR400L5

Carb diaphragms vibrating

Post by krystian579 » Sun Jul 16, 2017 8:44 am

Hi everyone, my first post on zxr world :smt001

I have a L5 which has been running a bit rough, revs kept playing up and it used to bog out on me a lot, especially from a stand still.

I went to a garage and they had a look and cleaned & setup my carbs, now it works a lot better but still not perfect, they said it will still run a bit funny sometimes (revs hang up for a bit when coming to a stop) and when going at a constant speed then pulling the throttle a bit, it coughs on me a little (until i pull the throttle more). Other than that, the bike pulls fine and gets through the whole rev range with no issues.

They said this is because the bike is old and the carbs get worn overtime, and that i could try a different set of carbs eventually. Now my thought was, when i had my airbox off at one point and started the bike, i saw the diaphragm slides vibrating up and down on idle, and when revving slightly they would be a bit glitchy.

Is this normal? or should they be dead still on idle, and moving up and down smooth when revving?
If its not normal then i think replacing my diaphragm rubbers might solve my issue, but want your opinions first before i spend money confuddled

Thank you!

rccaulfield
Posts: 48
Joined: Tue Sep 25, 2012 12:26 am
My Bike: zxr 400l sp
Location: Ireland

Re: Carb diaphragms vibrating

Post by rccaulfield » Sun Jul 23, 2017 9:05 am

thats normal, theres a slight vacuum on idle. Sorry but your mechanics talkin nonsense, sounds like your running too rich, propably on your needles, they need lowering a click and see if bogging down goes away., carbs dont get old, engines do. Time to learn the bike inside out using the manual or bring the bike to someone who knows what theyre talking about! A quick experiment would be to remove the snorkel if fitted on the entrance to your airbox, does this improve things? May even run a bit lean now, if so start taping up the airbox entrance bit by bit and see how she behaves.

krystian579
Posts: 2
Joined: Mon May 29, 2017 3:26 pm
My Bike: ZXR400L5

Re: Carb diaphragms vibrating

Post by krystian579 » Mon Jul 24, 2017 9:56 am

Thank you for your reply, but i think i managed to find the problem and fix it!

I went ahead and took off the airbox and turn on the bike to have a closer look again.

Turns out only 1 diaphragm was vibrating (badly) on idle, and the rest were still. when revving the bike, the bad diaphragm would hang up, causing too much fuel entering the cylinder (which will cause bogging out im guessing as well as high idle).

So i took the diaphragm out the carb, and i was missing the tiny brass air jet! either the garage or previous owner must of lost it :smt018

I ordered a new one from kawasaki original parts, put it together, and now all diaphragms work the same as they should :excited

I took it for a short ride, the idle is much better and i haven't had any bogging out yet, but i will take it on a much longer ride at some point and see if i get anything. As far as running rich, i think i am rich a little, as when i revved the bike to the limiter once, a lot of black smoke came out the back. But now the bike runs with no issues as far as i know, so it should be ok? I got a scorpion full exhaust system, k&n filter and running 95 main jets.

rccaulfield
Posts: 48
Joined: Tue Sep 25, 2012 12:26 am
My Bike: zxr 400l sp
Location: Ireland

Re: Carb diaphragms vibrating

Post by rccaulfield » Thu Jul 27, 2017 9:08 pm

excellent, I thought you meant the slides were vibrating, maybe you did? Anyway ur sorted best luck!

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