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hi all ive been out on the zxr400 since doing the resto and its not running 100% its spluttering around 5000rpm its fine once you get past the 5000 rpm mark and it get worse as the bike gets hotter ive never changed the plugs or blanced the carbs so i did that today and took it for a spin and its still just as bad theres no white somke and it ticks over a treat and starts fine. ive got a few ideas what it could be just want some input from you guys if you think these would effect it at all
1) would a kink in the coolent hose to the carbs cause any probs its a tight fit aginst the frame ?
2) i didnt clean the powder coating from any of the earth points the fuel pump one
3 ) and do the coil packs need to be earthed to the frame ie the mounting points do they have to be bolted to the exposed alloy of the frame
the tank was stored in my meatal shed for a few months it does get damp in the winter but i filled the tank on friday and surely wouldnt it be effecting the hole rev range if it was water in the fuel and the carbs where striped down during the resto and cleand
any help would be great

have you put new plugs in or just cleaned the old ones?

new plugs rob

it sounds like a cold 2 stroke around the 5000rmp mark

i had a similar problem but it wouldnt run below 4/5k, turned out to be plugs.

The hose for the carb heaters shouldnt cause you any problems.

The earth point might be worth cleaning up but mines the same and never had any probs, besides, the bolt that goes through should be enough.

Coil packs as far as i know dont need to be, they are mounted via rubber well nuts and like yours ive not cleaned any of the powder coating away.

If it were me id run some redex through. If still no joy id say gets the carbs apart for another clean and check. Check the diaphragms for splits too.

1. If it's the hose i'm thinking of, it doesn't actaully go to the carbs but to the back of the cylinders/water pump. So it could cause hotter running temps but probs not the spluttering.
2. I would check this first
3. iirc The coils bolt onto rubber grommets so are not earthed by the bolts.
Have you changed anything else that could effect jetting ie exhaust/ airbox?
Rob beat me to it lol

no the bikes the same as it was striped down and it was running fine before only things thats been changed is berings ect in the swing arm lol and thats not gonner cause any problems lol and its had new plugs today and and blanced the carbs today and they wasnt too bad
i must have upset something during the resto just dont want to keep putting it back together to find ive not cured the problem and have to start pulling it apart again
its got a full micron but had this on for 2 years with no problems and as far as i know its still running the stanard jets
thnks so far iam in the shed with the laptop i must look soo cool like i know what iam doing lol

must be gummed up carbs mate, especially if there was still fuel inside them when laid up! Like i say, bung some redex in and run it through.

how would i tell if it was miss firing or would it show on tick over as well ?

Just remember rob has shares in redex!!
Personally I'd check the carb balancing again as well. Mine was crap at about 6000rpm and that was down to carb balancing.

ok so ive just pulled the bike apart and checked the plugs that have only done around 10 miles and they are matt black really sotty ? running rich ? if so how do you alter it ?
thanks again kev

Matt black i think is an indication that its slightly rich, you can lean out the mixture by turning the mixture screws, i forget which way tho.... Have a check of the coils too, measure the resistance of them if you have a meter. They are probably fine but worth checking just to eliminate them out.

Going back to earths, might wanna check the earth on the top of the gearbox is nice n clean too

thanks rob i must add that i had the bike in bits last nite and this morning i was stood stratching my head and looked down at the bike with the carbs removed and one of the inlet rubbers wasent even bolted down so that would have been sucking more air in went out on the bike and it still splutters a tiny bit but no way near as bad think iam just gonner ride it for a few weeks now get holiday paid off and if its still not running 100% ill get some rolling road time booked some where

ok scrap that its still running like a dog i cleaned the tip of the exhaust it was free of carbon went out did 10 miles or so and pulled up and the tip of the exhaust was jet black and it stinks quite bad is it running rich ? iam fed up now

have you checked the float levels?