Modern Vespa

1980 Bajaj Barnfind

Upgraded the front spring to the stiffer one, and changed the inner tubes and tires to Heidenau k61.

Now the scooter feels very unstable, almost as if I'm about to lose control and hit the ground. It doesn't feel right - kind of too sensitive, and with wind - too scary to ride TBH

Any ideas? Is this normal?

Edit - I also tightened the fork nut as the fork had a slack - 1980 Bajaj Rattle Noise (Post 2649629)

rim mounted backwards ?

I'm not sure how that's possible

it is possible, you'd take the wheel off, flip it around, and reattach, deep side to the left and valve stem pointing to the right side of the scooter.

yours, however, is correct.

Tire pressure ?

Easy fix if it is. Check front and rear. Everyone has their own preferences, but I like about 25lbs in the front and 30-35 in the rear tire.

low tire pressure will feel like the bike is trying to drive itself into a ditch.

revert the spring? may be too stiff to do any good unless you are hard on the brakes.

Im with OTC.
Spring is suspect.
Perhaps it's not allowing the trialing arm to trail.
Instead it's very upright.

Can you post a pic. The other side so we can see the angle of the trailing arm?
Suspect it's kinda steep - and making ur scoot ride like it's on knife edge

I had 26psi on both. To my surprise, the front is supposed be at 17psi!

I also believe the stiffer spring is the culprit. I installed it to improve breaking, which was like non existent. And now I can tell that even though breaking is better overall, it does have a longer nose dive.

Not sure if you can see much here:

A stiffer spring would give less dive. No ? You should be able to tell by just pushing the front end down. Does it feel entirely different than before you changed it ?

Hmm, good point. I squeezed the front break lever and pushed the front end down. Yeah it feels like it takes longer, ie longer nose dive. Can't explain it

EDIT: I was ready to give up on this scooter couple of months ago. Maybe you've seen my other threads. Yesterday, I had more problems - it's just unreliable, even though I've replaced most of the parts. Yeah I got a good deal on it, but I have spent about 10 times more time working on it vs riding it lol

Yeah, the front is "supposed" to be at 17 (or 18 for Stella's and P's), but it rides like crap compared to more air. I guess that's good pressure if you only ride at low speeds on crappy roads, but not beyond that. Ditto the rear.

Try different pressures and find what works for you.

Also, that assumes like a 150lb rider and I'm over 200, so I adjust accordingly.

175lbs rider. I wish I could test ride with different tire pressure '80 Bajaj/Vespa Sprint Burning Oil (Post 2676216)
Lol

Hmmmm. If the steering is too tight the wheel will hesitate to move normally as the bike leans and will make handling feel awkward.. I don't know if you changed the bearings but old, worn ones will get dimples in the races from the balls and when you" take the play out" they sort of lock together.

Yeah that's why I brought it up. It's not too tight though and the scoot feels unstable when driving in a straight line at like 40+ mph. Basically it doesn't stay straight - like my body is not straight but constantly going left right, left right

Try loosening it up again. A bit loose and it will rattle . A bit tight and it will not steer properly. New bearings and races would probably do wonders.

This is true. I had my fork a little too tight when I first rebuilt the Boobadge and it was damn near unrideable until I loosened them up.

Unbelievable. That was it. Two adjustments and yes handling improved. Still there's some wiggle apparent especially when windy but it's possible it's me; I switch between riding my Harley (the Bajaj had sputtering issues) so it's normal given the 7 times weight...

Thanks for pointing me again in the right direction guys, obviously having the headset tight as my mountain bikes' is not the way to go with the scooter. (and I know what you're thinking - too many different types of two wheel "bikes"... I'd say too much residual information in my useless head)