Jetting On VFR400 NC30

[Dumbledore Calrisian]

As it stands, I've drilled the slides, pilot screws are 2 turns out, inserted extra 0.5mm washers in the needles, and... gone for #128F #132R on the jet front.
Long story short, bike bogs at the drop of a hat, In fact, I was riding towards a kitten in poor health and when it sneezed in my direction, the bike bogged again (no kittens were harmed in that altercation).
I did however find the power band, it's north of 13,000 rpm. Obviously, way way too rich.
Now the stupid part, the airbox is intact, what I can't figure out is where it draws the air from, that little ante-chamber in front of the air box that has a whole to the front of the bike is sealed at the top by the bottom of the air box. I hope u understand what I mean by that. It just seems like theres no air flow towards the boxes intake.
Should I leave box as is and get some much smaller jets?
Should I be drilling holes in the side of the box?
Should I be butchering the trumpets?
Should I rip out the rubber piece that looks like it's preventing any air getting to the boxes intake?
Bearing in mind, the bike does track but is also a street bike, needs to be rideable!
Oh, and for some odd reason it's running about 20 degrees hotter than normal, that really has me stumped, if it's too rich, why the hell is it overheating? My buns are steaming!!!
Advice,
anyone?

[CMSMJ1]

You need ot get back down to a 118 120 kind of jetting.... what you have is far far too rich.

Simple as that!

[Neosophist]

Whats your airfilter like?

Personally i'd go for smaller jets unless you have plenty of time and money to spend.

Airbox mods are more complicated than re-jetting. Look at the HRC carb tray / velocity stacks for some kind of idea.

[Dumbledore Calrisian]

yeah i have been, they seem to be holier than the pontif himself.

Air filter is a very light, very thin piece of foam, coupled with an after market can (sans baffles) hence i thought i'd need some serious fuel flow.

Was i very wrong then?

[CMSMJ1]

Pretty wrong..

You will want to leave it as standard as possible unless you want to go the whole hog.

Fit a proper filter, get the 118/120 jets and it should be good.

Also remember that bikes suck the air in and like it to be in a nice and steady state - removing pieces of airbox won't suddenly force any more air in - the engine will suck in what it wants. If it is sucking in on turbulent air then it will not be as efficient as sucking in on steady state air.

ram air is different of course...but you get the gist

for reference I run a bike with no airbox lid, RVF carbs, HRC tray, short stacks..blah blah - it runs 130 jets. if I pout a lid on it would be richie rich!

My race bike has a full standard airbox setup a 100% full race system and runs 118/120 - it is a touch lean, not a lot, but a touch.

[Dumbledore Calrisian]

k,
thanks for the prompt reply boys,
great info as usuall,
i'll stick in some 118 and 120s asap and will post again how i've made out.

[Cammo]

I did however find the power band, it's north of 13,000 rpm. Obviously, way way too rich.

Air filter is a very light, very thin piece of foam, coupled with an after market can (sans baffles) hence i thought i'd need some serious fuel flow.

Was i very wrong then?

No you weren't too wrong in your main jet assumption. Your main jets will be pretty near spot on I reckon. BUT your air filter will be causing the grief.

Without going into too much detail, the increased air flow that your filter will cause is meaning that the air jet and other settings will be way out. You can get the main jets and upper rev range to run properly (which is kind of what you're seeing over 13k rpm), but without changing other components you'll have a huge hole in the middle of the rev range. The hrc setup gets around this by restricting the air jets (and other add ons!).

All aftermarket filters will flow differently, from a bit more than standard to way too much without getting nasty on all of the carb settings!


Long story short, you'll have much better success if you replace the air filter with a standard one (RB Racing in NSW will probably have them in stock), and try 118/120 jets as said. PM sent.

[Dumbledore Calrisian]

K boys,
thanks again,
jets orderd, again,
will keep you lot posted after monday as to progress.
Heres hoping.

[Cammo]

K boys,
thanks again,
jets orderd, again,
will keep you lot posted after monday as to progress.
Heres hoping.

Hoping you'll be using a standard air filter with them!?

[Neosophist]

as i asked about the airfilter, its' the biggest way to buggar up the fuelling :D

The stock one is very good :)