Serious ZXR400 problems

[Rob W]

Well, as some of you may know I got knocked off my ZXR a couple of months back, and ever since it hasn't run correctly. Firstly the head gasket blew shortly after the crash and then I've started having idle/throttle problems.

Basically at around 4-7000 revs it 'chugs' as if it's running out of fuel, but above and below this it's fine. Also it will not idle AT ALL, if I set it to idle when I blip the throttle it goes up the rev counter and then as it drops back down it 'hangs up' at around 2000rpm for about 10-15 seconds before dropping back to it's idle speed. If I set it to not idle, the 'hang up' is non existent. I've had the carbs off, checked the diaphragm's and pilot's, cleaned them and checked the rubber mounts. Even replaced all the HT leads and one of the plug caps that gave a different resistance reading and it's done nothing.

If anyone's got any ideas they would be very much appreciated as I'm getting to the end of my tether now.
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'90 TS50 > '04 Senda 125 > '91 ZXR400 > '90 CB-1 > '04 GSX-R1000 > '96 Bandit 600 > '89 ZXR750 H1 > '96 GSX-R750 SRAD > '98 RR-W Fireblade > '98 T595 Daytona > '03 Hornet 900 > '04 Fireblade > '16 GSX-S1000F (x2) > '23 XSR900

[bish777]

Having a knock can loosen up all the dirt and rust at the bottom of your fuel tank.

Youll need to get your carbs of and clean them.

Invest in an inline fuel filter-a high flow metal gauze one.
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GSXR1100J

[Jrod]

The hanging at 2000 revs or so for a sec is normal, nearly every ZXR i've ridden does it.


The 'chugging' is probally the mixture giving you a flat spot. if it was fuel blockage it wouldn't rev cleanly the rest of the way.

[Rob W]

Is it possible that I have the wrong size main jet in number 1? Seeing as when I did the head gasket, I cleaned the pistons and barrels up and number 1 had been running rich. I then balanced the carbs and it's still doing it. I checked it by changing the plugs over and it's still running rich on that cylinder, and the plug that was in number 1 is now fine, whereas the number 2 plug that I swapped it with is showing signs of a rich mixture.
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'90 TS50 > '04 Senda 125 > '91 ZXR400 > '90 CB-1 > '04 GSX-R1000 > '96 Bandit 600 > '89 ZXR750 H1 > '96 GSX-R750 SRAD > '98 RR-W Fireblade > '98 T595 Daytona > '03 Hornet 900 > '04 Fireblade > '16 GSX-S1000F (x2) > '23 XSR900

[Kickstart]

Hi

Possible, and quite often the jetting is different between cylinders (normally the outer pair match, as do the inner pair).

However I would be more inclined to check the mixture screws and the needle position. Also check that there is not a missing rubber O ring between the caps on the tops of the carbs and the carb bodies themselves (common problem on Bandits).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Rob W]

Well cheers for all the replies people, gonna be stripping the carbs down fully at the weekend, so hopefully I'll be able to find out what it is doing it. Really quite annoying cos it makes the bike a pain in the arse to ride.
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'90 TS50 > '04 Senda 125 > '91 ZXR400 > '90 CB-1 > '04 GSX-R1000 > '96 Bandit 600 > '89 ZXR750 H1 > '96 GSX-R750 SRAD > '98 RR-W Fireblade > '98 T595 Daytona > '03 Hornet 900 > '04 Fireblade > '16 GSX-S1000F (x2) > '23 XSR900

[Rob W]

Well, just ordered a set of carbs for £82 and a new air filter and if this doesn't sort it out I'm going to be putting a sledgehammer through it.
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'90 TS50 > '04 Senda 125 > '91 ZXR400 > '90 CB-1 > '04 GSX-R1000 > '96 Bandit 600 > '89 ZXR750 H1 > '96 GSX-R750 SRAD > '98 RR-W Fireblade > '98 T595 Daytona > '03 Hornet 900 > '04 Fireblade > '16 GSX-S1000F (x2) > '23 XSR900

[bidman]

Hi mate, i see you have a micron end can on your bike have you had a dyno jet kit fitted and had it dyno'd to suit as this usualy sorts out any runing problems on the zxr400's when you fit a different end can it needs the dyno jet kit to so that you can adjust the needles and sort out the mixtures etc... but you sound like you know your stuff so just ignore me if youve already done this, cheers Dan
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Don't ride it, RAG IT!!

[Rob W]

I know bikes can need re-jetting if a race can is fitted, but it had that on before the accident and it NEVER did what it's doing now. Ever since the accident it's been running shite.


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'90 TS50 > '04 Senda 125 > '91 ZXR400 > '90 CB-1 > '04 GSX-R1000 > '96 Bandit 600 > '89 ZXR750 H1 > '96 GSX-R750 SRAD > '98 RR-W Fireblade > '98 T595 Daytona > '03 Hornet 900 > '04 Fireblade > '16 GSX-S1000F (x2) > '23 XSR900

[Barry_M2]

I think Keith could be right about the mixture, but you may also have an inlet leak. When you are riding along, take the revs to about 10k in 3rd or 4th, then shut the throttle, and with out braking, let the bike slow. Tell us what you hear.