Modern Vespa

My Tall OEM Vespa screen, which I love, requires I tighten the mounting bolts after every ride to keep it secure. It's not much of a chore to do, but...
Does anyone have any experience using Loctite Blue for this problem?
This might be a better solution than the risk of overtightening damage. Yes?
What seems reasonable may not be always the right thing to do, but if I'm lucky maybe there's only one good answer.

Loctite is bad for certain plastics, so I'd be careful. Some Harley guys use clear nail polish on their windshield screws. I would maybe try some Teflon tape or something first. Otherwise there's the purple Loctite (222) that is a step below the blue.

If the air pressure on the screen is working the bolts loose then yes, use it, but it come in different strengths, wouldn't go more than 243 medium, then in future its removable for maintenance.
Hope this helps.
Cheers.

Faster speed = More Pressure. Add longer rides and potholes... my 17mm gets a lot of use. I'm sure smaller shields have less of this issue. I'm happy to get these useful suggestions.

Good to know stuff here... Is the Teflon tape a logical idea or experience-based?

You mean it's actually coming loose or the installation instructions say to do that?

Tightened till firmly snug (no wobble), ride, and now they're wobbly and need re-tightening. Ride. Repeat. Ride. Repeat. Installation videos, i.e. Robot, suggest (!) that re-tightening is an expected user responsibility - just wasn't expecting to do it this often.

Take it to a dealer and have them show you how to install a windshield. You don't need loctite.

+1. Never used Loctite in a decade of riding with tall and medium screens on two Vespas ( Not all Vespa, to be fair. Occasional loosening, but once tightened properly, they stay.

Teflon tape is a sealant that is slick. Using Teflon tape on a fastener that needs to be torqued will allow a false reading that is low and will often lead to fracture of the components. Taping up your windshield hardware with Teflon will allow it to come loose more often or be overtightened resulting in damage.

It's not THAT complicated... I think all I need to get is a 17mm crowfoot for my torque wrench. You're right, I shouldn't need Loctite - that's why I raised this question.

Knowledge trumps theory. Thank you for this!

Bicycle shops sell a fluid that is a suspension of fine abrasive in oil. It is used to hold nuts and bolts on carbon fiber bikes where you can't torque the clamps down to avoid crushing the frame. The grit locks the threads to avoid loosening but is readily un threaded when needed. I don't remember the name but a bike shop should have it.

Keep in mind the original question, (vibrating loose after every ride) so taking into account can you acquire spare fixings for the screen, (not in my part of the planet) then replace with new, now take into account wear and tear from continual re tightening and thread fatigue also what type if any lubricant was used, then use a medium strength thread lock to pad out the thread and stop movement.
Also remember every nut, every bolt manufactured has a torque setting, over tightening is as bad as under tightening.
Cheers.

25% Off Sale at Harbor Freight - Crowfoot Wrenches are mine - mwahahaha!
Hope proper torquing makes a difference, 'cause hand tightening wasn't doing it.
RTFM: 35-40 Nn... We got this!

Carbon assembly paste. It isn't used on the nuts and bolts, it's used on the carbon mating surfaces to increase friction and hence decrease the needed torque on the bolts, eg for seat posts and handlebars.

How many millions of people have mounted windshields on modern vespas throughout the world without special salves, tapes or torque wrenches? It's not complicated. Tighten it down like you mean it.

If I lived in a scooter-dense area maybe I'd have someone to ask who would know such things. That not being possible, MV is where I go for answers. Yours are appreciated.

You wouldn't use that (Fiber Fix, et al) it's to keep seatposts and handlebars and stems from slipping. You might use something like Wheelsmith Spoke Prep which wouldn't effect a torque wrench and allows a fastener to be adjusted after installation. But I don't think you should need that either.

It's quite obviously the ethanol in your fuel making your screen come loose.

And I thought it might be all that Canadian smoke...

Well yeah. That too.

If it gets loose, that means you didn't tighten it enough. If it's getting loose while you are riding, you are lucky that you didn't hit a bump and have one side slip out. That's not fun.
Tighten it as tight as you can with a short 17mm wrench. Or try to use a clawfoot on your torque wrench and see what happens. You might not like the result.

Is it possible there is something wrong with the mounting hardware? Maybe a missing piece?

Or you might not have the mounting arms all the way "home" before tightening? I find I need to tap them in gently with a small mallet and then hold them at the bottomed-out position while I tighten down the bolts.

All good ideas, thanks!

Have you considered welding them?

UPDATE:
It appears to be my fault: the expanders weren't in the tubes all the way (actually flared so much I had to take the headlight cowling off 'cause they wouldn't back out through the holes).
Returning the expanding tubes (plastic) to their original shape with vice-grips and will try again.
Your interesting and helpful suggestions helped!
Lessons learned: it is possible to remove and replace the headlight cowling without removing the horn-cover bowtie (use a towel to keep things from falling into the frame). Without a magnetic screwdriver, use scotch-type tape to secure the screw and washer to the screwdriver. Be sure the cowling goes under the left grip's end - it'll have to be encouraged to go where it belongs.
Taking my time reshaping the plastic tubes... AHA - ScooterWest has them - maybe THIS is a common problem!? Buying new ones seems a better idea.
'We would recommended replacing these every few times you pull off your windshield. " Good to know.

not sure if it would work, but is putting the tubes in hot water an option to try and make them more pliable?

I always have at least a couple expansion cylinder clamp sleeves available and change them periodically. They are available from Scooterwest…sku# 65604500.

Because nothing is ever simple... the NEW sleeves work splendidly and I can get a secure 35-40 NM torque using them. I will order spares.
But doing so twists the shield seriously off-center!
I tried several ways to prevent this but it feels like this shouldn't be such a problem. I can stop some of it by putting an object between the shield and the headlight cowling while tightening, but this feels risky.
Any suggestions?