Running out of ideas with jetting?!

[glhboy]

So I have an 03 Ruckus, stock otherwise these parts:

RPM exhaust, Daytona variator, 5.5g rollers, Daytona CDI, KN filter on the stock snorkel tube, breather on left side of carb. Basically stock airbox eliminated.

I have tried all jet combos I can think of and can't get it 100%

Right now I am at a 90/40 and it runs ok. Will do over 40mph, but all through the throttle at anytime it feels like it cuts out or backs off. My plug looked a little white too...but if I go up to a 92 or 95 it doesn't seem to run any better if not worse. I have almost given up as I have spent 4 hours for the last 4-5 nights on this thing and can't get it right.

I have all 3 slow jets and all Main jets from 68-100 and most everything inbetween.

While testing the Mains, I found that a 95 gave me great top speed, but still cut/backed off and I couldn't find a matching slowjet that would give me the best combination....so I backed off the main and it would gradually run better, but not great.

any ideas?

[evilkaneval]

:)Well, I'm gonna assume you know what your doing with the jetting and know when your running rich/lean or just right. I have a few thoughts.

Have you cleaned your filter properly with KN cleaner and re-oiled?

How about placement of the filter? I read that you have it placed on the stock snorkel. Did you cut the snorkel back closer to the carb, or is it mounted where it once connected to the airbox? I wouldn't recommend either, but if you cut the snorkel back, that very well could be your problem.
When I designed my intake I of course did my research here at RuckCent.
During my research I found there was a lot of emphasis on trying to eliminate any turbulence in airflow. So, just to see what effect a stable air intake made, I tried several set-ups.
Direct on carb, on the end of the snorkel and cutting the snorkel halfway back to the carb. And just as I was informed the carb doesn't like the filter to close.
Which is what I would expect, I just wanted to find out first hand for my own experience and education.
Though its not bad to mount the filter at the end of the stock snorkel, I still think the more area and time the air has to stabilize and uniformly flow into the carb the better. If it is to close the amount of available air will constantly change due to wind and vibration. Think of it like trying to drink from a soda bottle while jogging It'd be much easier if you had a long straw(not recommend *chocking hazard*)
This may not even be your problem, but I'm on a roll here. Forgive me for writing an essay.
I guess what I'm trying to say is that your carb shouldn't be drawing air directly through the filter. It is better that it draws filtered air from a chamber or tube so that it pulls only the air it wants not what is thrown into it.

For example

Damn, thats one sexy intake.

[chanito]

ADJUST THE IDLE MIXTURE

[jedisabre7]

Aug 18, 2008 16:23:59 GMT -5 evilkaneval said:

. And just as I was informed the carb doesn't like the filter to close.
Which is what I would expect, I just wanted to find out first hand for my own experience and education.

Really, I can pass 50mph with the filter on the carb. Whoever told you that must want you to be slower.

[glhboy]

my KN filter is on the stock snorkel, I trimmed the end of the snorkel like sanjuro states on his post. It also has a bracket holding it to the cover so it's not moving.

[Dandy Dan]

I suspect your problems like with your slow jet / idle mix setup. As Chanito often says, your probably don't need to change the stock slow jet, you just need to adjust the idle mix screw a bit. Even with a big bore, people probably don't need to change the slow jet. I've rejetted a few other scooters since I had a Ruckus and I've learned the important of idle mix / slow jet adjustment like Chanito always preaches.

What I would do is put the stock 35 slow jet back in and then adjust the idle mix screw until it idles well (make sure it's warmed up before you do this). Once that's done, I would turn my attention to the MJ and probably bring it down a lot. A 90 main jet is high even for a big bore Ruckus...you're probably getting poor gas milage these days right? A 4-stroke can handle being rich okay but it does waste gas, slow you down a bit and it fouls plugs eventually. I suspect you want to be somewhere in the 35/80 range.

[glhboy]

Aug 19, 2008 9:56:10 GMT -5 Dandy Dan said:

I suspect your problems like with your slow jet / idle mix setup. As Chanito often says, your probably don't need to change the stock slow jet, you just need to adjust the idle mix screw a bit. Even with a big bore, people probably don't need to change the slow jet. I've rejetted a few other scooters since I had a Ruckus and I've learned the important of idle mix / slow jet adjustment like Chanito always preaches.

What I would do is put the stock 35 slow jet back in and then adjust the idle mix screw until it idles well (make sure it's warmed up before you do this). Once that's done, I would turn my attention to the MJ and probably bring it down a lot. A 90 main jet is high even for a big bore Ruckus...you're probably getting poor gas milage these days right? A 4-stroke can handle being rich okay but it does waste gas, slow you down a bit and it fouls plugs eventually. I suspect you want to be somewhere in the 35/80 range.

thanks for the info. I'm sure it is definitely using more gas, but more so since I have to drain the fuel bowl each time I'm jetting and I haven't been able to ride it much other than testing it out after each jet combo about 15 minutes.

I'm going to check tonight for vacuum leaks anywhere.

I have the stock snorkel on with a K&N filter on the end, a breather filter on the left side of the carb and a small breather on the bottom end of the car, par valve?, then the hose coming from the valve cover is vented underneath the bike with no filter and is zip tied in place facing away from the bike.

Since mine is an 03, I have to plug the vacuum line coming from the intake manifold right? That is plugged, but I'm going to check it for any leaks.

I don't have a tool to adjust the fuel/idle/air mixture screw...

[jedisabre7]

You can dremel a slot in the air/fuel meter and then use a screwdriver to adjust it.

[jedisabre7]

I would try a 35/88 and try adjusting the air/fuel screw.

[glhboy]

I decided to put the stock airbox back on tonight. I was running a 72 main when I had my Yoshi pipe with stock airbox...then I got the RPM and it wouldn't run right with the 72 so again I tried all jets I had, even down to a 68 and nothing.

It runs best top speed with a 75 and stock airbox, but man it misses/putters, whatever it is. I tried a 38, 40, 42 slow with the 75 main and stock box, but no go.

I give up, I really do. It was never this hard before. Never. I have literally spent hours the last 2 weeks every evening from 4pm til 8pm jetting, riding, rejetting, riding and on and on!

[Firegut]

You really need to adjust your idle mixture screw.
If it's in a bad position, you'll be running almost 5mph under normal and have really slow acceleration. Or, I found out, you'll stall at stops, but you'll be crazy fast top end. I bought a new screw that has a nob on the end so that I don't need any tools to tune it. More than once I've been riding and lost performance because of a change in temp. I can adjust it at stop lights.
My friends wonder how they can be beating me all day and then without notice i have the fastest scooter in the group.

[chanito]

I am still amazed at how few people take advantage of the simple most easy to do tuning aid on the carburator

[Firegut]

I never would have thought that tight tuning was so important. I suppose in larger engines it isn't, but in a small engine that is used at maximum capacity fine tuning is crucial. How often do you floor it in your car all the way up to top gear and stay there? I do it every on my ruckus.

[nbstunter]

i am having the same trouble i have this v8 pipe idk i got it off ebay, and i have tryed to up jet and it doesnt work. i am running a k&n filter right off the carb with the stock slow jet and a 80 main jet, runs fine with stock pipe at around 62 [KPH] on it put the other one on and it wont go past 40 [KPH] tryed bigger main 85 and still wont work, i have smaller main jets comeing in and im gonna adjust the idle mix screw in about 15 min thanks to this thread. any helpful stuff on this would be nice! thanks.

[Firegut]

You'll probably need a larger slow jet, but you can figure that out with the idle mixture screw.

[nbstunter]

how do i do that?

[Firegut]

If you tune by the idle and your best setting has the screw out less than 1 and 1/4 turns, you need a smaller jet. If it out more than 3 and 1/4, you need a larger jet. Just keep repeating the tuning with each jet, stepping up or down as need be.

[nbstunter]

your talking about the slow jet right?

[Firegut]

Yup.

[nbstunter]

how much is the slow jet used at high RPM? cause the bike runs good like doesnt spudder or anything but it has no power and slows does a lot going up hill