Misfire after 4k revs

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JamieNeve
Posts: 197
Joined: Fri Jan 25, 2013 12:33 pm
My Bike: CBR600RR, ZXR400 L-2
Location: Waterlooville, Hampshire

Misfire after 4k revs

Post by JamieNeve »

Okay here goes,

Basically when I start riding, all is fine, after sort of 5-10 mins of riding, when above 4k revs, the bike starts misfiring. Not quite sure which cylinder, but is definately misfiring.

Fairly new plugs+ stick coils

I have limited carb knowlege, but am I correct in saying that this is around where the main jet takes over from the pilot jet, so may be due to this? No idea what I would have to adjust though to sort out the issue!

Would like to ride down to Hastings on Monday, so need this sorted soon!

Thanks for any replies in advance!
JamieNeve
Posts: 197
Joined: Fri Jan 25, 2013 12:33 pm
My Bike: CBR600RR, ZXR400 L-2
Location: Waterlooville, Hampshire

Re: Misfire after 4k revs

Post by JamieNeve »

May also be worth mentioning, it is at it's worse when I try accelerating above 4k, sitting at it it sort of jumps in an out.

Also I have cleaned the carbs since and it is still doing it

Cheers
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banner001
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Joined: Sat Sep 24, 2011 3:27 pm
My Bike: ZXR400 L4
Location: Nuneaton

Re: Misfire after 4k revs

Post by banner001 »

are you positive its a miss-fire, and is not a loo-lean main jet?
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
JamieNeve
Posts: 197
Joined: Fri Jan 25, 2013 12:33 pm
My Bike: CBR600RR, ZXR400 L-2
Location: Waterlooville, Hampshire

Re: Misfire after 4k revs

Post by JamieNeve »

Definately sounds like it's misfiring i'm not sure of it, but it does sound like it's becoming the love child of a ZXR and a Ducati Panigale
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banner001
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My Bike: ZXR400 L4
Location: Nuneaton

Re: Misfire after 4k revs

Post by banner001 »

does it depend on the rate at which you increase the revs, if it depends on the rate it might still be carbs, if its not rate dependent i would say check your plugs, then check your coils, if you can isolate which cylinder its missing on it would be a big help as you can see if it moves when you move coils/plugs about.
UK ZXR400 L3 (1993) - Fully restored and on the roads, my green beast!
JPN ZXR250 A2 (1990) - Revs to 19,200rpm... 'nuff said :smt003
JamieNeve
Posts: 197
Joined: Fri Jan 25, 2013 12:33 pm
My Bike: CBR600RR, ZXR400 L-2
Location: Waterlooville, Hampshire

Re: Misfire after 4k revs

Post by JamieNeve »

It's definitely not coils- switched them with my spare coils and it still is present.

Have just finished completely stripping and cleaning carbs, will test ride in a minute and let you know!

Jamie
JamieNeve
Posts: 197
Joined: Fri Jan 25, 2013 12:33 pm
My Bike: CBR600RR, ZXR400 L-2
Location: Waterlooville, Hampshire

Re: Misfire after 4k revs

Post by JamieNeve »

Okay following your wonderful walkthrough, I gave the carbs another- far more thorough clean.

I then screwed all of the pilot screws in, and then out 2 turns (manual says between1.5 and 2.5) the misfire has now stopped, however it is idling at about 4k, a bit more pilot adjustment and hopefully it will be sorted!

Thanks Banner :)
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