1999 Yamaha Zuma CW50L

[dave54]

Hi, I am a new member to the forum and could use some advice.
I have a 1999 Yamaha Zuma CW50L that is giving me a headache.
Bought it a couple of years ago in pieces and have finally put it together.
I have purchased and installed....
Pollini 70cc big bore kit
Dellorto PHBN 17.5 carburetor
Pollini exhaust
Pollini high speed variator
new Pollini crankshaft seals
I presently have the main jetted at 90 and running stock air cleaner.
Motor starts easily and it runs well on the stand. Revs right up and returns to idle nicely.
When I test ride it ...falls flat on it's face....bogs down and will barely chug up my driveway.

I'm stumped...
Any thoughts / guidance will be appreciated.

Dave

[Zino]

what weights in variator and clutch springs light medium heavy or stock,torque spring light medium heavy or stock?

Did you derestrict the pipe ?

If you just go 1/2 throttle does it struggle or only when you go wide open ?

[dave54]

Hey Zino....no I haven't removed a baffle from the exhaust, I will sort that out tomorrow morning.
It bogs mid-range to full. I see that I can order a pollini roller weight kit with a variety of weights and try something other then the stock rollers. I did put a new clutch in it also....do you think I should make a change with the stock springs?
Thanks for your help/suggestions
Dave

[billwill]

That main jet sounds awfully large to me. I was running a 21mm dellorto PHBG on an MHR race cylinder with a 95 or 98 main (can't remember) and now I run that same carburetor on a milder street race cylinder and I don't think I'm running anything higher than an 80 main.

I might try to start lowering the main jet and see if that helps. Could also be some transmission tuning left to do. Especially if it is running nicely on the stand and not under load. I think you're still too rich on the main though.

I wouldn't worry too much about the clutch right now. Most of your problems are probably coming from carb and variator tuning.

[dave54]

Thanks Bill....will try a smaller jet.

[Zino]

On my Zuma and other builds
I had to run jets in the high 80s low 90s with stock Airbox and a 17.5 dellorto
the 19mm dellorto I ran low 80s with stock air box .

Fix this first
the polini pipe has one restriction in the pipe to clean out, it is right at the head of the pipe you can either Dremel it out or snap it out with a screw driver by wiggling back and forth

This is holding you back with it restricted it only lets a dime sized amount of exhaust which is choking your speed when you Dremel it out it will be quarter sized and will add to your upper and mid range .

I ran a very simialr set up to you for thousands of miles malossi wild lion (which is the same pipe as yours they are both rebadged gianelli go pipes )and a malossi sport cylinder which is in the same class as your polini sport a 17.5 dellorto carb
I have run both the malossi and polini variator they both work well .

Fix this next
As far as weights the polini variator ships weights at 6.7 grams
For your set up I would look at 5.5 grams to 6 grams with a stock torque spring .
You should not need to go beyond a stock or light torque spring
I would try the 6's first and see if that cleans up your own off throttle response .
You want the weights that give you the most responsiveness when you hit the throttle wide open along with the highest top speed

If you are rolling slow for 30 feet and then pick up speed try medium clutch springs ( polini Green ,Malossi yellow)
You want to take off with power when you hit the throttle wide open

[dave54]

Thanks for your input.
I did find the baffle in the pipe and removed it. I fired it up and the scooter is a bonafide rocket ship.
I ran it up and down my street and as I came out of a turn I applied throttle and the front wheel actually nosed up an inch or two off the pavement. Wow! I also own a Piaggio fly 50 and Kymco super 8 50 both 4 strokes and they are not going to keep up with this!!
I will address the roller issue next. Again thanks for taking the time to help me.
Blessings
Dave

[Zino]

Good to hear you are feeling the power now
Those pre bugs are very easy to wheelie

[dave54]

One last inquiry...
I removed the auto oiler and premix the gas and oil.
What would you recommend for a oil/gas ratio.
Thanks for your help,
Dave

[Zino]

With the good oils we have today you can run 50 to 1

[dave54]

I thought I was done asking questions for awhile.....but.
I am ripping around the neighborhood and tickled pink with this 99 Zuma.
Idle is off a bit...low and kinda chuggy.
Went to adjust idle screw and it really has no affect on rpm.
Am running a 88 main jet. Main jet screw around 2 1/2 turns out.
I got a roller kit and will be dropping the weights on Friday in the variator.
Thanks
Dave

[Zino]

idle jet if you cant get it in control in 3 turns out you need to try a smaller size pilot jet

the right right jet will let you fine tune between 1-3 turns out

some carbs don't have a fine tuning screw like the dellorto 17.5

so overall
I myself don't really mind a rich idle jet if I have spunky take off

[dave54]

Zino, thanks again for your input. If you lived in St. Louis I'd buy you lunch!!