NC23 flat spot at low revs, air box issue
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Please can you post items for sale or wanted in the correct For Sale section. Items / bikes for sale here will be removed without warning. Reasons for this are in the FAQ. Thanks
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Lucky13nz
- Settled in member
- Posts: 6
- Joined: Mon Feb 29, 2016 9:12 am
NC23 flat spot at low revs, air box issue
Hi Guys
Greetings from New Zealand!
Just purchased myself an NC23 in pretty good knick...
Unfortunately it has been sitting for some time and is in need of some TLC. I've started to pull things apart and am about to do a carb clean etc but it has a couple of issues I wanted to get opinions on.
Firstly, it has a flat spot when taking off. It feels like it is lacking power from idle up to around 2~2.5k rpm but after that it takes off like a rocket. It idles well and the throttle response feels good when just giving it a rev in neutral.
Secondly, when taking the air box etc off, I noticed that one of the previous owners had decided it was a good idea to bore 20mm holes all over the front end of the air box. I'm guessing he thought it might increase airflow (or something to that effect) but I'm of the opinion that if this was a good idea Honda would have put holes all over it as standard. Will this cause me any problems/issues?
Any thoughts/info is much appreciated.
Cheers
Luke
Greetings from New Zealand!
Just purchased myself an NC23 in pretty good knick...
Unfortunately it has been sitting for some time and is in need of some TLC. I've started to pull things apart and am about to do a carb clean etc but it has a couple of issues I wanted to get opinions on.
Firstly, it has a flat spot when taking off. It feels like it is lacking power from idle up to around 2~2.5k rpm but after that it takes off like a rocket. It idles well and the throttle response feels good when just giving it a rev in neutral.
Secondly, when taking the air box etc off, I noticed that one of the previous owners had decided it was a good idea to bore 20mm holes all over the front end of the air box. I'm guessing he thought it might increase airflow (or something to that effect) but I'm of the opinion that if this was a good idea Honda would have put holes all over it as standard. Will this cause me any problems/issues?
Any thoughts/info is much appreciated.
Cheers
Luke
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CB1pod70
- NWAA Supporter
- Posts: 302
- Joined: Thu Apr 09, 2015 1:55 pm
- Location: Gravesend
Re: NC23 flat spot at low revs, air box issue
As I've discovered, it doesn't take much to bugger up the carburation on these so I would advise covering the holes with Duct tape and see if that improves things before pulling everything apart.
Blair at Litek does a full set of o-rings and gaskets for not a lot of money when you do pull down the carbs for a clean.
Blair at Litek does a full set of o-rings and gaskets for not a lot of money when you do pull down the carbs for a clean.
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Lucky13nz
- Settled in member
- Posts: 6
- Joined: Mon Feb 29, 2016 9:12 am
Re: NC23 flat spot at low revs, air box issue
I'll give that a go but the carbs probably need a clean after sitting for so long.
Where is Litek?
Where is Litek?
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CB1pod70
- NWAA Supporter
- Posts: 302
- Joined: Thu Apr 09, 2015 1:55 pm
- Location: Gravesend
Re: NC23 flat spot at low revs, air box issue
http://litetek.co/Carb_Kit_Honda_CBR400RR_NC23.html
he's based in Thailand but don't let that put you off. I've had about 5-6 kits off him and never a problem.
he's based in Thailand but don't let that put you off. I've had about 5-6 kits off him and never a problem.
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richyrd5
- Regular Member
- Posts: 743
- Joined: Fri Feb 21, 2014 1:31 pm
Re: NC23 flat spot at low revs, air box issue
yes i would say that the holes are the cause of the flat spot(ive just bought a zxr with some strange mods/holes done to the airbox 
)that was standing for a while and had flat spots all over..soon as i put a standard airbox on and cleaned out the carbs its running spot on now,,so do as above and duct tape/replace airbox. 
)that was standing for a while and had flat spots all over..soon as i put a standard airbox on and cleaned out the carbs its running spot on now,,so do as above and duct tape/replace airbox. -
Lucky13nz
- Settled in member
- Posts: 6
- Joined: Mon Feb 29, 2016 9:12 am
Re: NC23 flat spot at low revs, air box issue
Awesome, thanks 
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Icemaestro
- Familiar Member
- Posts: 331
- Joined: Wed Nov 27, 2013 6:45 am
Re: NC23 flat spot at low revs, air box issue
Where abouts are you based? Looking at getting myself a project two of these, haven't owned one before, but lots of nc30s
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kiwi racer
- Settled in member
- Posts: 82
- Joined: Sat Nov 15, 2008 9:10 pm
- Bike owned: CBRs
- Location: New Zealand
Re: NC23 flat spot at low revs, air box issue
Gidday fellow Kiwi.
Have you checked to see what the effect of that end can is doing to the jetting , you may have to alter the fueling a bit to compensate , as for the airbox holes, they are ok when racing but on the road you dont use full noise all the time , try duct taping the holes drilled first to see it it improves things. Where are you in Kiwiville ? .
Cheers mate .
Have you checked to see what the effect of that end can is doing to the jetting , you may have to alter the fueling a bit to compensate , as for the airbox holes, they are ok when racing but on the road you dont use full noise all the time , try duct taping the holes drilled first to see it it improves things. Where are you in Kiwiville ? .
Cheers mate .