Malossi 136cc + phbl kit => problem at low RPM

Here is my setup :


-ET3 engine with.

-malossi 136cc

-malossi reed valve (cylinder) + phbl 24 kit (default  jets) 

-Cone filter

-needle on the higher clip


-mazu full circle

-Transfers matched

-polini evo II racing exhaust.

All spy, bearing etc are new.


If i do a stop and go 'full thorthle' : Great acceleration, no problem.


my problem is that when i ride in group at "lower" rev (< 5000rpm) for a little times.

I can not accelerate properly.  It's like if the choke is on, but after 4-5 sec, the engine recover a normal (great) acceleration.  idle jet to big ?

What do you recommend for idle jet ?


Another "problem", probably not related. the engine vibrate a lot between 4000 and 5000rpm espetialy when decelerating.  any guest ?


Thanks in advance

Ferretti Fabio




Is your sparkplug correct?

Have you tried to adjust the mixture screw?


Thank you


isn't 17 ok for ignition ? As i remember for the malossi 136cc the book say 21°. and i've read somewhere that for vespatronic you must add 4 to 5°. but maybe i'm wrong and that's why it vibrate so mutch. (with 17° i've practicaly no power at low rpm)


ps: thanks for the link, it will help for adjusting the mixture !!!

I use Bosch w3as silver and I am very pleased. Concernig jetting it is very difficult to say anything from the distance but as a guide I used Max jet 92 with ram air filter. and min jet 60. (in a phbl 24 reed valve to crankcase induction). Ignition 17.

And I have just received this:




any one from sip staff?

i've try sparks from 7 to 9.

and yes i have try the mixture adjustment. (realy hard to access it in the frame )

[quote user="alberogu"]

17º is for standard electronic ignition. If you have varitronic follow what the instruction recomends.


there is no instruction given with the vespatronic .. only wiring instructions.

the "book" of the malossi kit said 21°. but must i align to 25° ? ( 21° malossi book + 4° for vespatronic )

my phbl 25 have main 105 min 50 but i don't know the nozzle and needle ( it's the one given with the malossi kit carb and  intake direct reed for the malossi 136cc kit, so i think it must bee the right one for the kit). but i've try all needle position already.


17º is for standard electronic ignition. If you have varitronic follow what the instruction recomends.

For jetting malossi recomends for phbl 25, reed induction to the cylinder:

Main: 107, Min 50, Nozzle 264 AQ, Needle: D26 (in the second position), Gas valve 30.

Follow this and see what happens and share with us.



align your vespatronic on 22°BTDC at 2500 rpm.


The jetting should work with the info you have-  best needle for this set up is a D26