Primavera polini pronlem

[Kyle]

Hi,I live in Boston and I just rebuilt my 1974 vespa primavera motor with a polini 130 kit, polini reed valve conversion, and a dellorto 24 phbl24as carburetor. It has a 100 main jet, a 60 starter jet, and a 50 idle jet. I did not cut the crank because of the reed valve installation. I made all of the reed-valve kit alterations recommend by polini. It starts right up and idles well, revs well in neutral, but dies when I try to accelerate. I have been told this is the most knowledgeable scooter forum out there. Does anybody have an idea about what could be wrong?

Danke!

[Solstice71]

Hy, if you would really like to have a serious Support by the Guys, you should better translate your Problem by using something like The Google Translator or something. Not all of us know how to use special, technical English to explain, what goes wrong with your Engine- Setup.

But first of all, you should check your Jets by using this Site: http://sfs.alexander-hepp.de

Maybe your Jetsize to big or The Clip Adjustments wrong.

There could be a hole lot of Reasons to your Problem. Including The Crank!!

Then check your Ignition- on what Setup does it stand? This is really important!

Bearbeitet 14. Dezember 2010 von Solstice71

[Tom Turbo]

Check also your fuel supply - is the fuel hose probably bend anywhere?

[Eydsoab]

maybe also the mainjet is to big, try a smaller one. but go down in steps from bigger to smaller (something between 85-95 should be ok)

[amazombi]

Check the fuel line and the fuel tap. A kink in the line, or a tap blocked by dirt could cause fuel strarvation. Also check the carb, the flood bowl in particular. Basically any small passage from the fuel tank to the venturi of the carb could be blocked which could lead to problems like yours. It could be slightly overjetted too, while that will have an effect on the engine's performance this is not likely to stopp it from pulling in gear completey.

I'm not entirely convinved this is at the bottom of your trouble though. What's the ignition your using? Points still? If so, have you checked them, plus the condenser and the HT coil?

[amazombi]

Check the fuel line and the fuel tap. A kink in the line, or a tap blocked by dirt could cause fuel strarvation. Also check the carb, the flood bowl in particular. Basically any small passage from the fuel tank to the venturi of the carb could be blocked which could lead to problems like yours. It could be slightly overjetted too, while that will have an effect on the engine's performance this is not likely to stopp it from pulling in gear completey.

I'm not entirely convinved this is at the bottom of your trouble though. What's the ignition your using? Points still? If so, have you checked them, plus the condenser and the HT coil?

[Solstice71]

Off Topic:

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On Topic:

was sagt ihr evtl. zum Drehschieber? So wie ich des verstanden hab', hat der die Platte nicht zerfrässt, und kann evtl. somit Probs mit Überfettung bzw. Blowback bekommen-das kenn ich nämlich nur allzu gut.

Bearbeitet 14. Dezember 2010 von Solstice71

[Kyle]

Thank you for the information! The carburetor and fuel tap are new. The fuel line is pretty straight. I think over jetting could be the biggest part of the problem. That is what i will try to fix next. It has an electronic ignition from an et3 and I have the ignition set at exactly 16 degrees before top center. I exchanged the dellorto with a mikuni from my friend's et3 and it was a little better but still not good. It worked ok at the top of the gears.

[amazombi]

Solstice wrote that, as far as he understands it, you have not touched the rotary pad inside the crankcase. Is that correct? Or have you just not cut the crank, but did the work on the crankcase? If the rotary pad is still as it was when it left the factory, and the crank isn't cut either, you effectively have to different inlet systems, each obstructing each other. That could well explain your problem.

Still sorting your jetting isn't a bad idea. You could also slightly advance your ignition. Anything up to 20 is not a problem, and it helps the engine quite a lot at low rpm.

[Kyle]

I made all the modifications to the crank case that were in the instructions with the polini reed valve kit, including the removal of the rotary pad and matching the manifold to the case... Power at the low rpm would be very helpful right now, I will try advancing the ignition when I get some smaller jets.