Calling All Experienced Tuners! By magoconnor (Read 521 times)

[magoconnor]

Hello. 

I am writing to you about some problems I have with my scooter.

Kymco super 8 4 stroke 72cc.



I hope you guys can help me out.

My scooter do not really reach high rpms when I give it full throttle, as you can hear in this sound clip



Which in turn limits my top speed..



I have removed the following restrictions:

Cut one of the small wires at the cdi box.

New sliding tube and new polini variator 4.5 gr.



In addition to a 72cc bbk I've also fitted a larger cylinder head with bigger valves. I have had to increase my main jet size, following the installation of the new bigger cylinder head. Right now I'm running with a 110 which I think is pretty high. I have also tried higher and lower main jets with no increase in performance. The rpm does not go up nor does the top speed.



I have thoroughly checked for leaks but found none.

The scooter starts immediately and keeps idle fine.



Timing is correct and valves are adjusted.



My setup:

72cc gy6

47mm cylinder head 21 in / 19 out

Performance camshaft

Polini variator 4,5 gr

Unifilter

Leovince exhaust

15% stronger torque spring

Stock carburator

[czmdiver]

Take the Belt off and run it that way and see how she Tachs up.
Have you worked the throttle at the carb directly with your Hand to make sure the Carb is Opening all the way?
Also you need to get a cheap tach for her so we really know what kinda rpm's she is pulling, its also need to tune the Var correctly..

[czmdiver]

Question, I was looking at the Leo Vince web site and only found listed a Exhaust for a Super 8 50 Two Stroke, I didnt see any Super 8 50cc Fours Stroke.
Do you have the Two Stroke pipe on her? can you post a picture?

[magoconnor]

Hi man thanks for answearing.

I think I have boiled down the problem... maybe.
with the bike fully warm, I tried really going wot down a slope.
With only a slight increase in rpms and top speed. By the end of the slope still going wot the bike started to hesitate and backfire.
So the bike must still be restricted in some way, or possibly the cdi has gone bad.

I have cut one of the little purple wires, which is suppose to move the rpm limit from 7500 to 9000 rpm.
But Im getting nowhere near that...

Oh! here is a picture of my exhaust system www.google.dk/search?q=leovince+kymco+super+8&rlz=1C1AVFB_enDK752DK752&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjStsKs8JHbAhWHCSwKHXUTDY8Q_AUICigB&biw=1280&bih=697&dpr=1.5#imgrc=Gs-IYuQMEn9l3M:


Hear is a video (not my bike) showing that there still is a restricton when the wire is cut:
First: original cdi with the wire cut:

Second: Aftermarket unrestricted cdi

The question is what to do now?