Modern Vespa

Hi everyone,

I purchased a Bitubo Sport rear shock about ten years ago but only installed about a year ago. I might have done about 1000km with it.

It was installed as it came and I have never adjusted it. I would to adjust it for city driving, mainly flat roads with the occasional crack or pothole. I have px200 engine in a 60's largeframe, and weight 75kg 165 pounds.

What should I take into account and how should I proceed? I ride on my own will always do so. I want my Vespa to be as comfortable as possible. I can't compare but whenever I hit a pothole the rear of the Vespa feels super heavy, can't feel the rebound of the shock.

Here you have a couple of pictures if it helps.

Thanks in advance for your help and comments!!

It's not doing a hell a lot of anything on that setting!
Give it a half dozen full turns at least (about 1" of adjustment) & go from there.

Helps to have a helper. The shock needs to be "pre-loaded" to absorb bumps and rebound from potholes.

Sit on the scoot, centerstand up, and see how much the shock compresses. It should be somewhere near the middle of its travel. Turning the adjuster clockwise will put tension on the spring and make the ride firmer. Turning it counterclockwise will release tension and make the ride cushier. Too firm and it'll feel hard, too cushy and it'll bottom out.

Thank you, know I see what I need to do. What do you exactly mean when you say that the shock needs to be pre-loaded?

Thank you!!

"Pre-loading" is the process I just described ... putting enough tension on the spring when the scoot is stationary so that the shock can do its job of providing upward and downward dampening once you get on the road.

Get the spring out of a pen (or something that has a spring that you can COMPRESS)...
hold it between fingers, just enough tension to hold it there.... no pre- load (just like your shock), as if the rear wheel was hangingin the air.
Squeeze it till coils are all together & spring Squished as far asi it goes (& if there was nothing stiff inside the spring it would simply bend & fire across the room - like it just did)..= full load on spring, as if you are from S.E.A. & riding the vespa back from teh shops with entire family & groceries onboard. Ie bottomed-out.

Squeeze it about 1/3rd between those 2 points (& hold that tension) , so there's enough tension on the spring that it sits nicely between your fingers, but you can also add/reduce tension to it without it either falling out from between your fingers , or bending & firing across the room.... this is basic pre-load... the amount to tension on the spring when its sitting there waiting for you to hop on & ride, but the only weight is the scooter.

Squeeze it a bit more, ie to about half of the way (& hold that tension) ... this is pre-load ... ie where the spring sits while you're sitting on the scooter, also where it sits while you are riding along on a nice flat bit of road.

Now the fun bit.. move your fingers closer of further apart rapidly (ie "bounce" on the spring)... this is the load as you go over bumps, which would also be more/higher if you have the entire family riding along)... this is what you are adjusting...

if you go too HARD it will feel like your spine is compacting, or you're taking a pounding like going in a tinnie/small boat over waves.
If you're too OFT it feels like you're floating or bouncing all over the place, or it something keeps scraping on the ground after every bump.
ADJUST ACCORDINGLY ... & remember that its ok to change it regularly.
I adjust mine if going on long rides, carrying extra weight &backpack/pillion, on rough/gravel roads etc...

to understand STOCK ABSORBERS... add a bit of sponge between your fingers.

Great advice and explanations!

Please, shoot me if I get it wrong after all this detail!

I'll report back on the improvement once I get done. I lost the original Bitubo key and I need to get a new one...

If you can't feel the rebound of your rear shock, it's probably because it's working correctly. A Bitubo will have stiffer valving when compared to a old worn out stock shock. Since our scooter suspensions have such a short stroke, the suspension travel isn't as noticeable when compared to a motorcycle. I installed a YSS rear shock last year, and i think the instructions spec'd out 25mm for a minimum preload on the spring (I can't remember the exact lenght for sure)? There's also suspension "sag" that san be accounted for as well, but i have no idea if Piaggio even had a sag recommendation measurement. I weigh in at about 155lbs (with no gear on), and have always adjusted my rear performance shocks to the lightest preload setting.

Give the big fine thread thats showing inside the spring a good clean & add a bit of lube/WD40 so it will turn without sand & small grime jamming things up.
I'm Pretty sure theres a GRUB SCREW in one of the small holes (someone here will be able to confirm). Loosen it, then, get someone/someone to support the weight of the scoot (so theres no tension on the spring) & turn the silver thing.
It should turn by hand or use a bit of solid wire with the end bent over so it fits in the wee hole (or a tiny screwdriver, & possibly a tap with a hammer). If it jams, simply go in the other direction to unjam it & clean the thread a bit more.... if ya cant be arsed using a Castle Nut Tool, just get out the Pipe wrench

I have adjusted by 1" as SubEtherBASS suggested and then I´ll take it from here. I managed to turn the silver thing with ease with the help of small screwdriver, no need to have someone seating on top to atenuate tension of the the spring.

I'm noob with no previous experience on technical things. If I keep turning up the spring the rebound will be harder and I will notice it more?

And if I turn down I will release tension and the rebound will be softer?

With the 1" adjustment I can feel the rear of the Vespa let's say "lighter". How should go for a for a touring comfortable ride? I aim at a soft but firm rebound.

Cheers!

Go for what feels good ... your weight, condition of local roads ypu ride, how much you want to thrash it etc.
It's adjustable, adjust it... i change mine depending on what distance i ride, weight i carry, if its rough/bumpy, when on the dirt/gravel, when on the track, carrying a pillion, or just thrashing it... play around, you will KNOW when the setting is about right.

BTW: once you're feeling happier with the setup, invest in some nice soft sticky tyres while you're doing this, as you will be amazed at what a change it will make.

The MAJORITY of my tuning was done going to work & back... try to get a mix of roads/speeds/surfaces/elevations, even track down a few potholes/bumps on the way... ride to work... after work make an adjustment (& note what you did, only do 1 adjustment at a time), ride home & see if you can feel/tell the difference... ride back to work next day (clear head & you get more distance for testing)... after work adjust something & ride home..
It's great to do AFTER work, as you will work out how to do the adjustment in a few minutes & you will enjoy riding AWAY from work more, rather than just an automated ride home.

BTW: did I mention to change the tyres?
BTW: remember to go OVER potholes & bumps, you will find you can do it faster & without wobbles or concern once the setup is good , plus do a few good "swerves" so you can check overall handling.
BTW: timing your rides will also make them fun... ohh, sorry, that was supposed to read "it will help ascertain if its actually making a difference in overall performance as well", write notes