carbs

[ant75]

hi all, i was wondering if some1 could help me here, after testing numerous parts on my honda nc30 as it wasnt revving cleanly ive narrowed it down 2 a carb problem it has a full tyga race system. on it wil start first time and idle solid the carbs have 118 jets front and 120 in the back and are brand ,when i blip the throttle 2 5k its fine but it seems 2 bog down between 5-9 k then clears itself 9k onwards when it goes back down 2 idle it tries 2 die a little.
how do i get the mixture screws right so it revvs cleanly? i also put in a new air filter wich made no difference,carbs rubbers look good with no cracks, sorry for being a pain

[Jamboy]

I would consider running 120 - 122 main jets and see how you go with that if you have the full tyga exhaust. If the bike seems to have a flat spot in the mid range you could try a 0.5mm washer under the needles but sometimes there not needed all depends on the bike as some do differ.

As for the pilot screws if memory serves me right and I'm sure cammo will correct me if I'm wrong is 2 turns out as standard but try them at 2 1/4 turns and see how the throttle response is. If it's still not right 1/4 turn out at a time till you get it somewhere near but 2 1/4 - 2 1/2 turns is the norm.

Also worth checking is does the slides have the standard 2mm hole at the bottom of the slide next to where the needle comes out or has it already been drilled to 2.5mm as this help with throttle response.

Cammo has a carb setting guide at the top of the workshop section also worth reading if you get stuck

[ant75]

thank you for that i wil have a look at the slides,and reset the mixtures to 2 turns out and go from their,i do have a spare set of carbs with 115f and 118r still runs shit..

[Jamboy]

That jetting for that exhaust system is to lean which is maybe why you are having trouble. 115 - 118 mains is standard jap spec far to lean for this country.

[ant75]

so to richen it mixture screw out? screw in leaner?

[reverse cylinder jim]

Might sound a silly question but whats it like when riding? You mention about blipping the throttle and revving it but whats it like under load. Its not really good for the motor to rev it like that in neutral.

[Jamboy]

That's it but will only really affect low down revs I recommend 2 1/4 turns and see how you go.

[ant75]

ok thanks wil try that,not really ridden it as it was a project bike with no t+t but wil get out for a blast this wk end

[Cammo]

I hope you're waiting until the bike is warmed properly before trying to rev the engine. They don't like to rev at standstill until the water temp is hot, what you describe is similar to how a cold nc30 engine behaves when revved.

If you are warming it up properly and still seeing these symptoms, it's usually related to induction changes causing a lean midrange - removal of the rubber flap, modification of the airbox snorkel, cutting the front of the airbox base, aftermarket air filter etc. Check to see that you have part #13 in the link below:

http://www.cmsnl.com/honda-vfr400r3-199 ... _3000.html

Is it a standard Honda brand air filter that you're using?

If this is all standard then taker a look at the carb needles - there should be one 0.5mm washer under each needle as standard. An extra washer will richen up the midrange and can alleviate these sorts of symptoms, but really you'd be covering up the cause of the problem rather than fixing it.

As Jim says, how it runs can be very different when stationary it or riding it. Personally I wouldn't touch it until it's been ridden, you might just be creating more work for yourself.

[ant75]

thanks very much for that cammo,i do warm it up dont rev from cold,the only thing i notice is that the fan is not comeing on when very hot 90 c?,it does work as ive took it off 2 try it and its all connected up properly,i wil try rideing it this wk end and c how it goes,then il try the extra washer under the needle will i have to drill the slides? when i get it running got all the time and money ive spent on it wil b worth it..