variator or belt ?

help me get it to the top plz , 78 vespa grande rebuilt engine , new crank with needle bearing ,piston rings, seals , polini variator , 13/13 carb 68 jet, tecno exhaust

1556209137063524537377.jpg

Re: variator or belt ?

I swapped out my rear end on my '78 Bravo getting 35 mph WOT on the flat, with stock variator 13:13 carb,64 jet, Proma circuit pipe. Changed out variator weights also.

Re: variator or belt ?

so if u put heavy weights that r guaranteed to max out variation and it still doesnt get to the top. w belt off rear pully push variator all the way in and see if belt wedges to top. if it dont, whats stopping it, variator travel, inside cheeks, ramps,rollers, hard to say. did u grind out that plate that allows u to move the motor back? will help if u do.

Re: variator or belt ?

The flat on the rear pulley I believe is what’s keeping you from getting any further variation, I’ve been making rear pulleys for my bikes with a steeper angle to get the belt all the way to the shaft resulting in about 8mph increase in top speed.

E735BF73-40D6-45EC-9A6E-454F7FFC9679.jpeg
52B0D549-A4A2-49F0-A7EB-79D7AC3A2B40.jpeg
0F6B2FCC-9DE0-4359-A4EA-2E52279997E5.jpeg

Re: variator or belt ?

If your using polini or malossi variator springs you may need to grind the spring a bit to get the cheeks to open more. Treats sells the cnc variator pulleys which look to be the same thing I’m making for my bikes.

https://www.treatland.tv/vespa-piaggio-CNC-d-steel-racing-driven-pulley-pla-p/cnc-vespa-pulley-plates.htm

Re: variator or belt ?

Also check to see if the moveable variator cheek is bottoming out on the stationary cheek before the belt reaches its highest point, I cut the faces of my variators at a steeper angle to help the belt ride higher. But I’ve never had a polini.

Re: variator or belt ?

Are you missing your rear engine mount bolt? Also drill out those rivets and remove that locating plate so the engine can be slid in the slots. Try to get your belt to the top of the rear pulley by sliding the engine back.(edited)

77593707-B0E1-4B90-A173-C0B8A62887C0.jpeg

Re: variator or belt ?

thanks for all the great advice , lots to implement and experiment with hopefully it gets going like ot should

20181130_101000.jpg
« Go to Topic — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account