cbr400 nc23 Please Help Bigger main jets?

[cbr400]

I'm pretty sure Graeme will have sent you Dynojet jets, is that correct? Size 112 Dynojet jets are equivalent to around 115 standard Honda jets. 118 sounds big to me. The popping is due to excess fuel combusting in the exhaust, possibly because of running rich, not a symptom of running lean unless I'm mistaken. A little bit of popping when off the gas is not unusual. Graeme has sent you the right jets to get you in the right area - to adjust your fueling further you need to get the bike on a dyno to get a reading of the air:fuel ratio over the rev range.

Just to check - is your airbox standard/unmodified, standard filter? Standard needles and heights? Trumpets? Float heights? Pilot screws? Carbs been cleaned recently? You need to make sure everything is clean, working and set to standard to help diagnose a problem.

all standerd apart from jets and exhaust

[sa.racing]

i have s/steel downpipes into a very wide car exhaust pipe

Can you post a pic of the system on your bike, if the link pipe diamiter is too large it will sap loads of power mainly from the midrange, do you know who made the system?

[cbr400]

OK HERES THE PICS if anyone needs more let me know and if someone can identify the make of this exhaust it would be much apreciated

[sa.racing]

Those downpipes are made by a company called DK motorcycles they are complete shite and they are the reason your bike has no midrange, your best bet is to get rid and fit a second hand set of stock NC23 headers or a decent s/s system if you want your bike to run properly, drop Graeme (GF Racing) a mail he should be able to sort you out this was a very common problem a few years back when DK were selling them on ebay but after all there customers complained about how shite they were they stopped making them and I haven't really seen a set in a while guess your just unlucky ...
Simon

[cbr400]

Those downpipes are made by a company called DK motorcycles they are complete shite and they are the reason your bike has no midrange, your best bet is to get rid and fit a second hand set of stock NC23 headers or a decent s/s system if you want your bike to run properly, drop Graeme (GF Racing) a mail he should be able to sort you out this was a very common problem a few years back when DK were selling them on ebay but after all there customers complained about how shite they were they stopped making them and I haven't really seen a set in a while guess your just unlucky ...
Simon

still dont explain the popping and firing on de-excelleration?

[petrolhead19]

still dont explain the popping and firing on de-excelleration?

its alright my bike does that always has done even with standard pipes, so did my blade, do does my brothers r6.
i wouldnt worry too much about the popping and firing, just see it as something to shit the biddies up with lol :D

Adam

[cbr400]

still dont explain the popping and firing on de-excelleration?

its alright my bike does that always has done even with standard pipes, so did my blade, do does my brothers r6.
i wouldnt worry too much about the popping and firing, just see it as something to shit the biddies up with lol :D

Adam

but its either undefuelling or over fuelling and must be contributing to the flat/sluggish spots ?

[petrolhead19]

the reason it pops is because it has unburnt fuel passing through cylinders into the headers were it then ignites, which suggests over fueling .

Doesnt bother me too much though i like the popping sound, either that or if your exhaust has a slight blow in it some, were you might not even be able to hear it blow, but if it does then the extra air mixing with the fumes coming through the exhaust system makes it pop.

Check to see if your exhaust is blowing anywere even if its slightly blowing it can cause popping, ifot tn its over fueling.

Adam

[cbr400]

the reason it pops is because it has unburnt fuel passing through cylinders into the headers were it then ignites, which suggests over fueling .

Doesnt bother me too much though i like the popping sound, either that or if your exhaust has a slight blow in it some, were you might not even be able to hear it blow, but if it does then the extra air mixing with the fumes coming through the exhaust system makes it pop.

Check to see if your exhaust is blowing anywere even if its slightly blowing it can cause popping, ifot tn its over fueling.

Adam

nah done a smoke test on exhaust cheers though m8

[GF Racing]

As I indicated earlier - those headers do not work in the midrange ... that's why I requested the picture !!

Simon is spot on.