Jetting questions

[white wings]

Hello all from the states,

I had a very successful first year on the track with my 1995 RVF400 that I bought as a training tool for the smaller tracks. I typically ride a RC51 on larger tracks but a few scary moments the year prior prompted me to go back to the drwing board and advance my skill even further before pushing harder on the RC.

With that being said, most of my knowledge is in FI bikes with Carburation being a second if not third language to me. I have researched untill my fingers were numb on the right formula for the right weather when adjusting the jetting and tuning the carbs prior to race day and still feel like I am just not getting it right.

Now I know all bikes are different and my bike is no exception to the rule. Since my acwisition of the 400 V-4 I have completley made it my own.

Front end was modified to allow for a complete RC51 front end with ohlins internals, HRC pipes mated to a Tyga Maggot can (thank you Tyga), CF bodywork, CF HRC copy airbox, HRC intake funnels, speedcell battery, brembo front brake master, Sato clip-ons with CF tubes, Ohlins rear shock, HRC box, Carrozaria forged AL front wheel, Alth full floating front rotors, HRC soft bite pads, braided lines all around, HRC rads (upper and lower), as well as some small stuff that I am sure I forgot.

I just need help with jetting! Is there a formula or calculator out there somewhere to help get into the ball park so I don't fowl plugs and blowing flames?

[Indiana Jones]

Just have to ask,that track looks like Jennings,Fl.
Am I correct?
I've been there with USGPRU and a few track days.

[Neosophist]

There are no doubt equations that would allow you to work it out but I imagine it'd be rather complex.

Factory Pro have a decent guide, have you read their tuning CV carbs article?

http://www.factorypro.com/tech_tuning_p ... gines.html" onclick="window.open(this.href);return false;

I suggest going over that first, if you follow it from start to finish you should be pretty close, some quality time at a dyno will help as they'll have the right equipment to help monitor and sort the Fuel / Air mixture.

Do you currently have standard RVF carbs or are they different?

[Cammo]

Jetting is heavily based around induction changesd on these bikes. It looks as though you have a larger airbox and the short intake stacks and thats about it.

What jets/needles is it running now? Do you use a filter? Need more info...

Get the main jet right firstly, then move on to needle and pilot screw. Pilot jets and air jets won't generally need to be changed on your nc35 carb setup.

Once you get the jetting in the ballpark, you can easily adjust up or down a size or two to suit changing weather conditions.

[Neosophist]

As Cam said, air intake mods really affect the bikes jetting.

If you post some more details about your airbox etc setup someone on here will be able to advise you on where to start :D

[white wings]

I love this site as much as I do the speedzilla.com site!
Thanks for your responses guys/gals(?)

I am running a k&n style renewable filter and yes the funnels are shorter in stature and dimpled if that matters. Although most of the track NC35's I've seen seem to bi-pass the added air possible with the upper fairing to the front of the tank tubing on the stock NC's I chose to keep them for appearance more than potential function. I also added the HRC try the fits under the stock carbs (answering one of the above questions) and lips over the top rad to allow for cooler air to fill the space around the carbs. (I wish I could find my pics of this process! )

I can't find my paper copy journal of the specs including the jetting on the bike. I recently moved and have not got my shop organized the way I need it to sleep well at night.

When I bought the CF bodywork from a bloke in the uk he sent the HRC undertray, airbox, funnels and a SHIT TON of jetting hardware all in sealed HRC packages. When I sent my stock NC35 carbs off to be worked on, my guy did't use any of the jetts I sent along with the set up as the jets seemed to be fine. Just a simple cleaning (simple for him) was all it needed.

The bike was being run without a choke assembly which I thought was very strange since I could see the choke cable sticking out under the frame where it should be. After removing the carbs I noticed the previous owner or owners had removed the linkage connecting the choke cable to the TB'S. (WEIRD!)

[Cammo]

A set of nc30 hrc carbs I got from Japan also had the choke mechanisms disconnected, not sure why.

About the only part of your induction setup which will affect your jetting over stock is the k&n filter. I imagine this would be freer flowing over the standard paper type and you'd require larger main jets. That's about it really.

What makes you think the jetting is incorrect?

[white wings]

great question and based on your comment, I feel a bore measurement of the carbs is in order to make sure
i have the 35 set and thise larger ones off a nc30.

To answer your question, I have riden felt and heard Nc30/35's that have far more of the expected gear whine I have come to know and love from owning MANY honda V-platform motors. I know this bike was set up to run endurance races but I refuse to crack the covers (other than the clutch ) to check for an increased bore. I was having a problem keep plugs dry after the rebuild/cleaning of the carbs as well as having a serious pop and flame under engine load (downshifting). Again, I am still learning the pro's and cons of Carb of EFI and will not give up. I did a full year of track time the way it is with very limited adjustments. I just don't think I would trust anyone this land locked in the USA to look at a bike more commenly found on the coasts her in the US.

The bike isn't as smooth as I've heard

[Cammo]

The nc30 carbs have metal slide covers and black rubber intake stacks, the nc35 carbs have black plastic slide covers and metal intake stacks. It sounds as though you have nc35 carbs if the stacks have been replaced with shorter hrc items.

The engine should be smooth all through the rev range. Exhaust popping on the overrun is common though because petrol is still going to the carbs when the throttle is shut (unlike your EFI!).

Does your engine rev out cleanly to redline in all gears?

A good thing about these bikes is that nearly all issues can be fixed through a process of elimination (albeit sometimes a lengthy list!).


Edit: FWIW I reckon the nc35 carbs are a shedload more forgiving whensetting up for big induction changes than nc30 carbs!

[Cammo]

I was having a problem keep plugs dry after the rebuild/cleaning of the carbs

Do you think it was fouling them at idle (pilot screw too rich) or at speed (main jets too large)?