How-to adjust the STOCK keihin NVK cv carb

[chanito]

I am giving up on you guys using the idle mixture adjustment I keep reading most people do not do it and that is really sad, as doing it makes for a much easier to ride scooter, swaping carbs before using the full potential of the stock carb suxs
Getting a tool to adjust the mixture is cheaper than getting a set of slow jets I personally use it to take the idle mixture screw, cut a slot on the head and then just use a long flat head screwdriver to adjust it, as it is much easier than fighting with the socket on that hard to get at place, but anyway come on guys adjust the mixture before getting into jetting or swapping

[rattmobbins]

Apr 23, 2008 19:27:38 GMT -5 chanito said:

I am giving up on you guys using the idle mixture adjustment I keep reading most people do not do it and that is really sad, as doing it makes for a much easier to ride scooter, swaping carbs before using the full potential of the stock carb suxs
Getting a tool to adjust the mixture is cheaper than getting a set of slow jets I personally use it to take the idle mixture screw, cut a slot on the head and then just use a long flat head screwdriver to adjust it, as it is much easier than fighting with the socket on that hard to get at place, but anyway come on guys adjust the mixture before getting into jetting or swapping

Not so fast chan man. I'm gonna adjust my carb this weekend using your tips, so they aren't TOTALLY falling on deaf ears.

My Ruck hasn't run that great since I bought it, and I'm thinking this might take care of her. Plus I'm psyched about the possibility of rockin' an intake and exhaust without re-jetting!!! RPM here I come!!! ;D

[Dandy Dan]

Chanito....I'm really becoming converted to the idle mixture sermon you've been preaching for years now. Last summer when I was adjusting the idle mix I didn't realize it was such a finely tuned adjustment so I was adjusting it in huge increments (i.e. changing it by a complete rotation at a time). I re-read your post here today and idle mix tuning makes a lot more sense having read that. I feel like a bad guy for my utter neglect of the idle mixture over the past couple years but now I understand it much better. This past weekend I spend a few hours adjusting the idle on my Beluga (with the help of a former motorcycle mechanic) and I now understand it better since i've actually done it in real life. I'm sold on the idea of adjusting the idle as the first step in rejetting.

[varroa]

chanito, i didn't post it, but i did use your method.

last friday, i installed K&N main filter, and after installation of the new main jet, i adjusted the mixture first, and then went on a run.



by the way, if i let off the throttle as much as you showed, and SLOWLY start loosing speed, what is it? is my jet spot on?

i am asking, because my ruckus does not a)go faster, b) sttuter, then recover, or c) stay the same, as you described.

[chanito]

Yes you are ;D ;D ;D

[sr50r]

Hey here's a question:

You never mentionned what you look for on the vacuum gauge when doing a pre-06. Y'see I've got the tall order to jet my first carb ever: my sister's 03 ruckus, and hey, I'll take any advantage I can get.

Also, this might sound stupid, but I only see 2 types of jets for sale online: PC20 jets (I know what that is) and C4U jets (I dont know what that is), the stock carb is a keihin nvk (which doesn't rhyme with c4u), and when I ask google what a C4U carburetor is, I can't get a coherent answer.

I dropped by a shop earlier today and was advised that my best bet to get jets for the stock carb was a honda dealer... So as we say on some other place I often frequent: what's the sauce on stock jets?

[jedisabre7]

c4urself

[chanito]

Battlescooter store sells set of main jets for the stock carburator.
What you are looking with the vacuum gauge is the highest vacuum while adjusting your mixture, just go slowly and let the engine set itself before adjusting again

[ppaauull]

probably a stupid question, but want to make sure...

chanito's method:

"1.- leave the idle or slow jet stock (that is 35) and set the idle mixture, if it takes more than 1 full turn out to adjust it right then go to the next size up, if not, LEAVE IT ALONE"

for the SJ, how am i setting the idle mixture? go on a test run to see which setting is optimal? optimal for overall speed/performance?

once the SJ is set and working on the MJ, we're then not touching the idle mix? if lean, upjet the MJ, rich, downjet MJ? or we're turning the idle mix again to fine tune the MJ?

[chanito]

I gues you forgot to read how to adjust the idle mixture, which should be the first adjustment on the carb and you do it with the scooter standing still

You will need a tachometer good enough to measure idle speed variations of 50 rpms, and a calm head, go for a ride of at least 10 minutes, to make sure it is fully warm up, Now we need to lower the idle speed by using the idle speed adjustment screw on the right side of the carburator, this have to be done to prevent the transition ports to be uncover by the throttle and messing our adjustment, and to make it easier to judge the changes on the engine, So lower the idle speed to
1600 rpm, then slowy screw the idle mixture adjustment in, until the idle drops 50 rpms, then screw it out past the original position until it drops 50 rpms again, now is just a matter of setting the screw right in the middle of those two places and set the idle speed back to 2000. Congrats, you just adjusted the idle mixture on your scooter

After adjusting the idle mixture then you mess with the main jet

[typer126]

I'm running a Leo Vince exhaust and a Kajima intake on my Ruck. I've been using an AEM wideband to help with my jetting, but I've run into a problem. I'm currently using a 38SJ and a 90MJ. It runs good and A/F ratios are solid, except when I'm cruising. With the throttle barely cracked my A/F goes extremely lean. Adjusting the mixture screw to get rid of this leaves my acceleration soft. I'm can't decide if shimming the needle, or cutting some coils from the spring would be the best solution. Any suggestions?

[JWS]

OK this is good good info, but I want to know what is stock for the Idle Mix Screw? If I seat the screw all the way in how many turns out will get me to stock. I have messed with it and it is running fine, but do not know if I am more that one turn out from stock.

[chanito]

It is 2 and 1/4 of a turn

[rdcox23]

Great info, thanks for posting.

I'm working on an '06 that I just bought and it has trouble starting. Shoot a little ether into the air intake and it will fire right up and run.

I'm currently working on removing and cleaning the carb. I will then try to adjust it properly.

[lupoone]

my metro has good idle good low range and good mid range throttle response but nothing after that any suggestions

[Ping51693]

Recently put a carbon yoshimura pipe on my 2013 ruckus and it feels very strong everywhere but i am hitting rev limiter at 40mph. Im 180lbs i used to hit 45 with stock pipe. Any suggestions? Any help would be great thank you!!!

[devind12]

Hey there long time Ruckus owner, I have been doing mods for the last couple years and finally I just got to do the intake and re-jetting, I have messed with the fuel and air mixture but now it won't even turn over. I have taken the carb apart cleaned it and put it back stock and still nothing. When I started I could get about a1/4 turn in the throttle before it started bogging out. Anyone have any ideas. I have a tach and it appears to be working. I currently have a yoshi carbon fiber exhaust, polini variator with5.5 g rollers, a larger kn off the carb, and a breather on the left of the main,  and the pair valve and the PCV valve breathing off of one breather. ANY HELP? I thought I had it today but then it continued to crap out.

[ahmad]

what is the dual little hoses conected to each other by a single thing

[chanito]

Please post a pic so I know which hoses are you talking about

[texasliam]

The adjustment tool MN08-0242 is more easily found by this number
08-0242.