vespa small frame gearing

[sean brady scooters]

friend of mine has just stripped down his smally motor due to various probs /none performance...
and has found that amongst other things it may have been slightly over geared.
its an ET3 main case ,although it has a missmatched outer case half...
running a polini 135 kit on 4 speed gearbox ,cut crank...approx 180 degrees of inlet timing..24mm carb and PM pipe.
cases have not been matched or ported .so std.
primarys are 29/68...hence 2.34:1
i assume this is way out myself and have advised him so (maybe std primmy pimarys would be better or others to give maybe a 2.55/2.6 :1 ratio) but would appreciate some advise from others just to give him a second oppinion as hes very confused about it all.

[Robi]

Match the casing, and a 2.56 for road use, a 3.00 for race.

And you can put a DRT gearing shaft to mount both around 2.86



For me 2.34 is to long for an "small" engine, and you can never pull the 4th...

[Wayne Miller]

friend of mine has just stripped down his smally motor due to various probs /none performance...
and has found that amongst other things it may have been slightly over geared.
its an ET3 main case ,although it has a missmatched outer case half...
running a polini 135 kit on 4 speed gearbox ,cut crank...approx 180 degrees of inlet timing..24mm carb and PM pipe.
cases have not been matched or ported .so std.
primarys are 29/68...hence 2.34:1
i assume this is way out myself and have advised him so (maybe std primmy pimarys would be better or others to give maybe a 2.55/2.6 :1 ratio) but would appreciate some advise from others just to give him a second oppinion as hes very confused about it all.

Hi Sean,

Either standard primmy primarys 24/61 or 27/69 should give you around 2.55
24/61 = 2.54
27/69 = 2.56
Tell him to get a short forth too

[tony]

Sean if you run 27/69 you have a 3 further options of drt primaries that will interchange. 25,26 and 28.. in fact he may even do a 29 now.. wayne is right with the drt 4th.. this sounds good with the 27/69

Robi.. that gearing for race is way too low for the uk tracks btw.

[Wayne Miller]

Ive not seen the 29 yet, but I'll be buying one to play with soon Tony

ps DRT also do a 24 for use with 27/69

24/69 = 2.88
25/69 = 2.76
26/69 = 2.65
27/69 = 2.56
28/69 = 2.46
29/60 = 2.38

[Robi]

Robi.. that gearing for race is way too low for the uk tracks btw.

Oups

I forgive you run on long track

In france, we race on short track (approx 1/1.5 km)

[sean brady scooters]

thanks for the replys everyone