Horizontal Yamaha zuma build sputter issues

[239prebug]

I recently built a 2 stroke zuma motor to swap on my Honda ruckus frame. After I got it all together it ran great I did a few heat cycles and took it for a ride down my road pulled great and had lots of power. Problem is I’d be going down my road and the carb would run out of fuel and the bike would turn off. I’m using the ruckus oem fuel pump and got a pulser module to make it work I figured out that my fuel cap was not venting and I was getting vapor lock. I fixed this issue but now that I figured out why I was running out of fuel the bike acts like it’s running rich sputtering when I pull on the throttle. I’ve dropped a few sizes down on the idle jet and it hasn’t made a difference at all. I’m wondering if I could have messed something up from it running out of fuel when I was having vapor lock issues. I have a CP 21 carb with 104MJ and down to a 34 pilot now with no change needle clip is all the way up top.
Polini corsa cylinder
Stage 6 crank
Yasuni c16
Polini bearings and seals
V force reeds
360 intake
CP 21 carb
Thanks for any recommendations!

[pili]

Just wondering if having fuel pressure from the pump vs gravity feed might be causing problems? I don't think the vapor lock issue would create residual problems.

[Zino]

I'm with pilli I dont think vapor lock would have any carryover effects once you fixed it
Try dropping and raising the main jet to see if it runs cleaner when you hit the throttle

[239prebug]

It originally ran perfectly until the bowl on the carb ran out of fuel it did this 4 or 5 times before I realized it was vapor lock from the gas cap not venting. I’ll try going down on the main jet but I’m getting sputtering on quarter to half open throttle wide open it eventually clears and pulls hard again.

[Zino]

That should be the needle at 1/4 to 1/2 throttle

But lets make sure it is not a transition from idle to needle.

Try this to test idle mixture
with it well warmed up .
Let it idle on the stand or at a stop sign .

Note rpm speed (if you have a tach this is easier)
Blip the throttle .
3 things will happen

If idle speed drops below regular idle speed and then cleans up and rises back to normal you are on the rich side for idle mixture you could adjust a notch leaner.
The rpms drop back to normal speed real quick
This is close to perfect
The rpms stay above normal for a little bit and hang there you are lean .

Then I move on to needle than and take the position that is most responsive at 1/4 to 3/4 throttle.

[239prebug]

I did a lot of changes on the carb today probably took it off over 10 times I went from 40 and worked my way down to 32 on the idle jet I also worked with the main jet went from 106 and worked down to 100 every change was one at a time I even went from middle notch on the needle and eventually leaned it out to the top notch lean as it would go every change I did I would end with the same result lots of sputtering on take off and it doesn’t quite clean up even at wot. I’m not sure what’s going on I had it dialed in at the beginning and I got the sputtering symptoms the last time the scooter ran out of fuel when I was at wot. Ever since that last time it ran out of fuel I’ve been dealing with the sputtering issue. I even had the motor off the bike and did another leak test and it held 8 psi for around 30 min. Not sure if something got damaged in the cylinder head or reeds yet I was hoping to not have to break it down again but seems like I might need to investigate. My last effort is going to be taking the carb of another scooter I have with the same cylinder and see what that does I’m also going to add another ground from the motor to frame if I get the same result then I will be pulling the motor apart unfortunately

[239prebug]

Got it fixed! I put on a new ignition coil and now the bike is running perfect again! I played with jets for to long and not a difference every change I was getting bummed out about it. Now I can take off with no hesitation no sputtering just a perfect smooth 2 stroke I’ll be doing a few tweeks to the CVT and see what kind of top speed I can get, already hit 58mph and it’s definitely got more in it.