Calling All Experienced Tuners! New video and pictures

[dexameth]

18mm carb, with 115 main does seem a bit large. Even with the checking of the air leak, I would STILL suspect an air leak somewhere and the extra fuel is making up for it. Also, have you played with the needle clip setting? That will help with midrange. Start it on the top clip, do a run, and start moving it down one notch on each run until you find the adjustment you like.

[magoconnor]

I will check again.

My stock carburetor is without an adjustable needle.
But I could use shims to raise it, but how thick should I go?

[dexameth]

May 10, 2018 10:55:11 GMT -5 magoconnor said:

I will check again.

My stock carburetor is without an adjustable needle.
But I could ,use shims to raise it but how thick should I go?

Try a couple millimeters first. Or... have you thought about a new carb? Click me for a true 20mm venturi carb for your scoot. Comes pre jetted (hopefully for your setup) and has an adjustable needle. 

[magoconnor]

I would love to get my hands on that carb, but with import taxes its just way too expensive.

I would try with a couple of mm.

What do you think of the plug?

[GrumpyUnk]

+ If it hesitates on acceleration, it's not likely too much air, but too little fuel. Either pilot jet or accelerator pump...
BUT
You are lean on the 'top end' also... so that says, to me, check the float level. Does the float 'drop' all the way, and allow full flow? If you invert the carb, does the float measure properly from float bowl gasket surface to the top of the float? There is a 'spec'.
When you open the throttle, air will move quickly into the intake vacuum. Fuel, liquid, being more dense will accelerate slower, and lag the fuel flow. Accelerator pump squirts extra fuel to let the fuel catch up to the air flow.
Fuel is pulled by vacuum in the venturi. Low level, and a given Hg of vacuum will pull less than 'normal'.
Check float freedom of movement and level. Find the setting in a 130QMB shop manual(on site).
tom

[magoconnor]

Hello.

I have checked thoroughly for air leaks and found none.
The bike is just hungry I guess...

I will try and raise the needle a bit and see what happens.
I have checked the float level and it seems to be fine.

[KSR Moto]

Check your compression

[magoconnor]

I dont have the tool to measure it, or els I surely would.
I think is good thou.. But thanks for the suggestion.

[KSR Moto]

Can you find someone that has one?, you must start from the basics if you came across something and cant figure it out

[magoconnor]

I will see if I can get a hold of one.
I will upload a video later, so you can hear the bike running.

[diynuke]

you could get one of those glass spark plugs. with those you can watch the color of the flame.

Or just get a wideband sensor but those are way more expensive..
and watch out tuning with a spark plug. just having the idle very lean will result in a white plug. no matter what size main you have on there.

So how do you ride when checking the spark plug? Full throtle than keyswitch off and then look or just riding slowing down letting it idle and then look?


And i would say just tune it at full throttle and then adjust the gas needle. and then maybe go 1 up or down..

[jackrides]

What is the spark plug #? What engine? Does it consume much oil? Does the float bowl have a drain line? If so, will 2 ounces of gas come out in 4 minutes or less? (Yes, you can suck on the vacuum line to the gas valve.) If not, that's the problem.

[greginisn]

Have you checked the vacuum diaphragm that helps operate the throttle slide? look for a poor seal around the edges, splits, holes - even pin hole sized?


As for the plugs  have you seen this chart?


 




It may help you make a decision. But as you mentioned the 115 jet seems grossly big for 72cc. You are getting into the gy6 150cc range with a jet that large. But what ever works and doesn't mess up your motor.

Greg

[magoconnor]

Hello.
Thank all of your guys for chirpping in.

Diynuke: I will try to do some wot runs when it's hot and then shut it off and checked.

Jackrides: My spark plug is a brand new ngk cr7hsa. My engine is a kymco super 8 ( 139qmb). It dosen't seem to be consuming oil. Yes the float bowl has a drain line. I will try and see what happens.

Greginisn: Yes I have checked the vacuum diaphragm, and it looks brand new, nice and rubbery.

[magoconnor]

I took the bike for a ride today, and tried playing around with the airfilter.
Still has the 115 main jet installed.

Here is my airfilter: www.google.com/search?q=polini+air+filter&client=avast&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj9x8Oe1v7aAhXC2CwKHRd4BSYQ_AUICigB&biw=1920&bih=949#imgrc=Z2DPeSNbx0VNBM:

The air filter has a " cap" which can slide on to act as a protective cap, which always blog of some of the air, atleast it says so in the description.

bike fully warmed up:

With the cap: lots of hesitation / hiccups on all throttle positions execpt wot. From stand still to full throttle no trouple, but the bike dosen't seem to be reving out. Well lets i'm not going in into super high rev's

Without the cap: The bike felt and sounded alot better. Only small hiccups on 10%-20% throttle, but the bike ran much smoother and I was able to get a higher top speed. some variation in torque some times it felt strong at wot. Other times I had to back off and come back up. Still not getting the desried revs.

Without the cap it's getting more air, so something is really weird here.
Because a 110 main jet was worse..