How to tell if you have a 20/25/30 mph Vespa

Jeremy Calton /

I've searched the forums here, but my Bravo has no sticker on the frame and the stamped "vin" plate and covers are missing. Reading it on the bike would obviously be the preferred method... :)

So, I found some awesome information on this at Myron's Mopeds worth posting:

http://www.myronsmopeds.com/wp-content/gallery/encyclopedia/info-vespa-7.jpg

http://www.myronsmopeds.com/wp-content/gallery/encyclopedia/info-vespa-6.jpg

Attaching as files just in case the URL's go 404:

info-vespa-6.jpg
info-vespa-7.jpg

Re: How to tell if you have a 20/25/30 mph Vespa

Jeremy Calton /

So I'm trying to definitively tell if I have the notorious 20 mph model. Since we've upgraded the pipe, carb, and variator to get it from 17 mph to maybe 28, it seems likely. Sad, since all I really wanted out of this was ~35 to make it my main transportation in-town.

The problem is, the 20 has gear (etc) ratios that you can't fix with upgrades.

My 78/79 stock Bravo came with a 12.7 carb and 39 jet, so it's definitely a 20 or 25 mph model.

How do I calculate the belt or rear hub ratio, so I can tell definitively where this project is heading? [See jpg #6]

The other thing would be if someone could tell me the difference between the stock [see #7] pulleys and gears. The 25/30 are all different from the 20, so if I could distinguish even one of those, I'd know...

Re: How to tell if you have a 20/25/30 mph Vespa

pick a spot to watch on your rear wheel. now slowly turn your clutch by hand and count the number of times the clutch makes a complete rotation to one rotation of your back wheel. 45T main gear is 11 turns of the clutch to 1 wheel revolution. 45T is a zippy acceleration gear ratio, but not a good top end one.

as far as i can tell from your spreadsheet things you posted, the 20mph version was 15 to 1.

get an olympia gearset off treats and that'll help a lot with top speed. also, look up grinding the brass bushing of your front variator, that'll help pick up a little acceleration after you put those new gears in. but better yet, just get a performance variator (such as a malossi multivar and polini speed control) and you'll see a world of difference, especially when combined with the gears.

good luck, and have fun

Re: How to tell if you have a 20/25/30 mph Vespa

+1 for swapping gears.... its soooper easy to swap the gears in the rear vespa variated tranny no matter what belt/pulley ratios you have. You can get stock 30 gears or the speed gears from treats. my 20mph bravo will long grade into the 40s wot on its best days but will also reliably 30+ alllllll day flats on the commute.... hi comp ciao head on an overbored stock 49cc cylinder to 60cc and a polini 41mm piston, 12.12 carb, mid/hi 50's jets, 9.x:1 speed gears, brass bushing mod, malossi 13mm toothed belt, still deciding on the permanent pipe choice and havent notched the variator yet.

Re: How to tell if you have a 20/25/30 mph Vespa

Jeremy Calton /

Thanks!

My rear hub ratio is 11:1 so I have the regular model.

Unfortunately it still only goes 32 with a Polini variator, Malossi belt and filter, Tecno pipe, and clean Dellorto 13.13 carb. [Petcock and fuel filter are also basically new.]

From what I have heard/read, it should be going ~40.

Front wheel is out of true, but I'm assuming that's max 1 mph. Don't get me wrong, I still need to fix it.

I need to check the intake, maybe it can be increased. Slowly learning...

Re: How to tell if you have a 20/25/30 mph Vespa

even if you're running a 13:13, it won't matter unless you have the intake opened up to 13. I'd say you're looking at 35 on the flat and 40 down hills if you open up that intake and keep those 11:1 gears.

You can also deck the head a little to get some more compression which will help.

« Go to Topics — end of thread

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

Login or Create Account