zzr600 stuttering problem

shea1980 · L Plate Warrior Joined: 03 Sep 2020 Karma :

Guys my 1997 zzr600 has a problem,I have balanced the carbs cleaned the carbs(jets),New air filter plugs etc,But when the bike is below 4000rpm(while riding,fine when reving it at standstill) the bike stutters and and doesnt run right at all,but above 4000rpm it runs great,Also guys the tick over of the bike is fine also,Would anyone know what the problem might be?Thanks all
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shea

jeffyjeff · World Chat Champion Joined: 02 May 2020 Karma :

If the bike did not exhibit these symptoms before you worked on it, you might have unintentionally caused the problem yourself. Carburetor jets are notoriously fickle, and you might have buggered one or more jets in cleaning, especially if you tried to ream the jet bore with a drill bit or a welding tip cleaner, etc. If that be the case, new jets are in order. The main jets take over to supply full power fueling at around 4000 rpm, so your issue could be related to the jet needles. Inspect the needles and main jets to ensure they are free if all debris, needles set to the same height in the carburetor slides. Make sure no slide is hanging up in its bore. Also, synchronize your carburetors at or near your normal cruising RPM.
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History shows again and again how nature points out the folly of men - BOC

Tankie · Crazy Courier Joined: 24 Feb 2017 Karma :

Did you check the plug gaps before installing?
Also check the caps were fitted correctly
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Always learning, everyday is a school day

redeem ouzzer · World Chat Champion Joined: 06 Oct 2015 Karma :

oilyrag · Nova Slayer Joined: 07 Oct 2020 Karma :

Did it only start happening after your carb work? Does it improve if you put the choke on?

jeffyjeff · World Chat Champion Joined: 02 May 2020 Karma :

Jozzer · Two Stroke Sniffer Joined: 14 Jun 2019 Karma :

Is the airbox sealed properly ?...

Had the same issue with mine when I bought it (2003/E11) over time the pressure of the tank pushing down on the top of the airbox along with the heat generated from the motor causes the airbox to warp and gaps to open up allowing unwanted air in, fairly crucial on these due to the ram air system...

The first place to look would be along the bottom of the carbs where they meet the airbox, this can be seen from the side of the bike and any air being drawn in through here will cause the same symptoms you are describing, coughing and spluttering bellow about 4-4.5k then suddenly it'll clear and the bike tears off up the road like a scalded cat !...

I had to make a couple of braces to go inside the airbox so as to clamp it down against the carbs properly...

Don't make the same mistake I did and immediately start chasing a non existent carb issue, been there, done that...