Looking for more top speed

[Zino]

if you are having trouble starting it with carb cleaner your carb settings are not right.
I ran stock air box
The dellorto 19 with 40 pilot and 82 main purred like a kitten and I got my best top speeds .
Going bigger on the pilot than a 40 hurt my throttle response and gave me sluggish take offs .
Jets in the high 80s would give me lower speeds than low 80s
My cylinder head temps on long 30-5 mile wide open runs would settle around 340-350 degrees .

My build was almost identical to yours
I ran malossi 70 cc yasuni r and gears .

Do you have a rpm or temp gauge .
Both would help with tuning .

[yanaha]

Last week I tried a 40 pilot and it fixed my issue at take off but it never started by itseft like a 45. Maybe I should unscrew the mixture screw more. I’ll try the 40 again tomorrow and play with it more. I don’t have any other gauge than the stock speedometer.

[Zino]

You can use a gps app on your phone so you can measure to the tenth of a mile for speed
For baseline tuning
I run the fattest main jet and work progressively leaner and take the jet that gives me the best top speed and responsiveness.
If 2 jets feel the same I take the richest one.

Try this to see if you are in the right range of a pilot
after the scooter is real warmed up

With it idling blip the throttle a few times
3 things will happen
1)the idle speed will hang out a higher speed then normal
This is lean and you need to go richer by turning the air screw richer
2)The idle speed will drop back to normal almost immediately This is perfect for a daily rider
3)Idle speed will drop below normal speed and then clean up ,Racers like this because after they come off of wide open throttle They get a blast of extra rich fuel for cooling purpose to keep from seizing

For a daily rider go for 2 first 3 second
Racers take number 3

You want a pilot jet that you can control between 1 to 3 turns out with the mixture screws

Do the wide open throttle test .
On race day we used this to make sure we had right jetting for the day
after your scoot is well warmed up .
Try running wide open on a flat surface a few times
Back off the throttle by 1/4 turn.
This will make you a notch richer temporarily .
3 things will happen
1)Rpms will rise or speed increases .This means you are a notch lean on the main jet and need to go up a jet.
2)Rpms/speed will drop slowly this is close to spot on
3)Rpms speed drops fast this is a notch rich try a leaner main.

For the needle
I just go for the most responsive on and off throttle position if 2 feel close to the same I go with the richer needle setting.

[repherence2]

are you running the Over range kit or are you running the Multivar?

[repherence2]

May 14, 2023 8:41:07 GMT -5 Zino said:

Do you have a rpm or temp gauge .
Both would help with tuning .

...if only they knew...

temp for carb tuning. 

tach for CVT tuning. 

the best $100 in tuning tools you could ever have.  longevity, reliability, and maintenance indicator.

[yanaha]

Thanks Zino for your help. I just give up and sent it to a mechanic to check it. I’ll let you know when its done.

[yanaha]

So welcome back, the mechanic didn’t even touch it in 2 weeks so I brought it back to home. I played with pilot and checked the float, was in specs (16mm) so I put back the stock carb and wired a temp and tach gauge. With the stock carb with a 92 main jet the temp stayed at 240-245F at wot with a top speed of 76 km/h. Is it safe to downsize the main even if the stock is a 80-82?

[Zino]

You have room to drop the main

how far are you running wide open a block or a couple miles at a time ?
If more than a mile you are running on the way rich side .
for refernce on my zuma i always let it warm up to 140 degrees before take off my first stop sign is just under 2 miles away.
My temp gauges gets breaks 300 degrees by the fits stop sign .
The next one is 4 miles away i will then drift up on that run and hold in the 340 range .

since you have a tach
use that to help find your main jet
do high speed wide open runs on the same 1/2 mile stretch
progressively drop jets
track peak rpms
as you go down your peak rpms will rise and then level off on a couple of jets
so for example
92 jet 8700 rpms
90 jet 8900 rpms
88 jet 9100 rpms
86 jet 9200 rpms
84 jet 92000 rpms

for a daily rider i would look at 86 over the 84 its richer
now the double check you would use is after this is make sure your temp levels off below 350 with that jet on long wide open runs

[yanaha]

I did about 16km of wot in two shot of 8km. I put a 90 this morning and redid the same test. The temp stayed between 250-257F and the rpm raised from 9200 to 9400 and dropped to 9300 after few km. So judging by what you say I will put a 88 and go for a ride again. I’ll order another set of main jets because my lowest is a 88.

[Zino]

8km is a good healthy distance for testing wide open blasts
The biggest key with the temp gauge is you want to see it just level off and hold a temp for long periods .
Since the fuel mixture provides about 80% of the cooling on these air cooled beasts .

what jets are you using mikuni or dellorto ?

with genuine mikuni 85 -88 was a sweet spot for jetting with the stock carb for me with stock airbox.

[yanaha]

I have Stage6 jets kit and I ordered a Polini 10 pieces kit (80 to 98). Maybe that brand have other spec than dellorto or Mikuni? I came from my test with the 88 from Stage6. Temp was climbing 273F after about 10km and stayed there. Rpm started at 9600 than gradually dropped to 9300-9400.

[Zino]

Sounds like you are closing in on the right jet
My bet a 86 or 84 will be the right one

When you switch over to polini start with 88 just to make sure it is in the same range as the stage 6
It should be but it pays to be careful as you are getting closer to the right range

Polini and stage 6 make dellorto jets that fit the Yamaha carb

[Zino]

hellish has tuned quite a few scoots he is using the same method to dial in his kymco
49ccscoot.proboards.com/thread/29836/zx50-rescue-alive?page=3

your getting close to right on with your jetting on the main
the tempature jumps with a bigger gap from the last jet as you get real the other big clue is your rpms are starting to find a upper range

[yanaha]

I tried the 86 from Polini, it got to the same temp but it was pretty windy. My top speed was about 82 km/h with 5.75g in the Multivar and a yellow contraspring from Malossi. I got 5mm left on the variator. I will try heavier rollers maybe some 6g or heavier tomorrow if the weather allow me to.

[Zino]

too avoid chasing 2 demons
your close on the carb
stick with the 86 if you are moving onto dialing in the cvt

I noticed you have the oversize variator up front ,If that is 99 mm across ,the stock belt will get travel on the 97 mm variator to under 2mm .
Does the variator hit under 1mm left on the inner edge of the variator ?
Do you have shims to change the length of the drive boss to adjust the travel on the variator ?