Modern Vespa

Picked this up pretty cheap so was expecting a fair few issues. I'm sure I'll have more q's about restoring this going forward but the first issue at hand is a rusty frame. Quite bad in some areas and the engine mounts concern me.

I made a rough cut where it had been eaten through.

Who has been through the same sort of thing, how did you tackle it and what kind of cost was it for welding? Cheers.











Last edited by Japtastic on Thu, 16 Mar 2023 17:10:42 +0000; edited 1 time

Just replaced the floor pan on a vbb, looks very similar. It was pretty straightforward but welding the rusty, tissue paper thin metal takes a while to get right. The panel was about $50 plus shipping, paid more in gas and rods to get it dialed in.

Decided it was time I learnt TIG. Going to take a few months before I can tackle the repairs my self. I do have some MIG experience but this is a whole new ball game. Definitely an art, have just practiced for around 8 hours so far.

In the mean time I've stripped the bike and grinded down more rust. I'm not sure weather I'll go the repair route or new floor yet. What do you reckon?

Looks good - practice is the key here and don't be afraid to drop the volts very low for tig here.

I don't think you have much to lose by trying the repairs, especially since you only have to weld 1 side and nothing will be visible from above. I'd definitely cut the end section near the cable routing or weld a thicker piece over the swiss cheese action that it looks to be.

Thanks, yeah I'm going to start making some cuts tomorrow to get rid of the Swiss cheese

It's not pretty but it's progress and better than dropping balls of molten metal all over the place like yesterday 😂 Got lots of these spare bits of 1mm sheet metal around to practice on.

Also, I'm presuming I can cut this join / dirt and water trap and replace with a flat piece of metal up to where I've marked?

Looks great! I would stop a bit shorter up the wheel well and make sure you mark / redrill the routing holes.

I did one of those.

The replacement panels for those are pretty good.

The hardest part is the seam.


Mine had a lot of rust, so I had to cut up pretty high.

after removing

It needed repair to the frame channel, too. I didn't see this until after removing the floor, but it was paper thin.

The rear fender is a separate piece, and just made a patch.

Just plug welded.

The top seam is the hardest part. If you can avoid the curve and just replace the flat part, it's easier.

The Carlucci ones are really nice. They have all the holes drilled for the rails and center stand. It's very hard to position those.

On the P, you can also just do the whole floor/legshield.

This is the later style, so the brake pedal is different, but otherwise the same, and the whole thing could be spot welded on. Much easier than plug welding.

This is awesome work and great information, thanks!

Do you use TIG for the seem? So you plug welded where the original spot welds were for the floor?

How did you get the frame completely stripped? I've also found previous bad repairs under the fuel tank where some one has put this kind of chewing gum stuff all over the seems creating a rust trap I'll try to get a pic later but no way to get a grinder or dremel in there successfully.

I used a mig welder. A 110 volt one with very light wite (0.30 I think?)

You stitch it, and eventually fill it in.

I had to watch a lot of videos, and practice a lot.

I think tig welding is better, but more skill.

I drilled holes where the old welds were, and plug welded those. Just in the sheet metal.

To get the old welds off, I used a mini belt sander.

I kind of overdid it. I cut out the bad metal, then had it blasted to get rid of the rust.

I painted the insides of it. And had the whole thing blasted again after the welding was done.

The second blast was cheap, though. The shop recommended it.

The hardest part, strangely, was fitting the floor rails. I had to drill new holes, and they needed a lot of adjustment.

Yours doesn't look as bad, though. It might be possible to just replace smaller areas.



This video was super helpful for the mig technique

If you replace the whole panel, you can do it this way. But It's probably not necessary. If it's just the flat part of the floor, it's pretty easy to do with the plug welds.




First blast

Insides painted.

touch up blast.

The replacement panel

The replacement panel

Before. It didn't have many holes, but the rust was pushing the seams apart.

Looks like a cracking job. What cost was the sand blasting? I'd like to do it myself but doubt any place would allow that.

It was expensive. It cost like $700, but I had them blast the whole bike, and powder coat all the non-body parts – wheels, fork, trim. It was like 20 pieces.

Just blasting the frame would have been around $100. The Bay Area is super expensive, too.

It's quite nice though. It removes everything, so much easier to work with.

Yeah it does look worth it for sure. I'm looking in to the ones you can buy to see if any would work satisfactorily.

The place I used had a large blast cabinet. It was like shop ones, but big enough to fit the frame.

It's a powder coating shop, and they do big industrial machinery.

Blasting with the kind of setup you would use at home is slow going. I have found it useful for rust that is really hard to get to or when a wire wheel, etc. won't get the rust off.

It seems like you might be considering spot repairs rather than doing the whole floor section. Sometimes this works out better, sometimes it's easier to replace a whole big section.

You might strip as much as you can to get a better idea of how far the rust goes. One of those cheap boroscope cell phone cameras is a good way to look inside the tunnel. You would want to avoid wasting time blasting metal you would be removing anyway.

Got one on order so will see how well it does on the hard to reach seems/areas.

I did remove some sections with lots of rust as you can see. Most of the badness is gone now leaving just surface rust.

I have a good view of the tunnel now and looks really good.

The plan is to sand blast all the areas I can't get to and see if it shows up more rust that I currently can't see.

Got some sheet metal ordered too so if all goes to plan I will start playing around with shaping and cutting it in preparation for my welding to get better!

I've got the rear support saved as that was ok, just the metal underneath was rotten.

That doesn't look too bad at all!

Thing to check (hard to tell) is if there's rust inside the seams.

If that's the case, it will look pillowy at the spot welds.

And check the frame tunnel on the inside close to the seam for pitting, pinholes.

It's hard to tell if water got inside the frame, but maybe not.


The braces are easy to replace. The Euro shops have them.

These things are nice, bc they're all stamped.

Yeah, I'm hoping no more in the seems but hopefully the blasting will reveal it if so. The tunnel is super clean through out which is great.

Didn't think they sold those struts so will order one with a few other bits for the sale of £12 it doesn't make sense to try and patch this one up.

That looks better than I thought it would. You should be able to get the tunnel nice and clean now with more access to it.

Yeah there is a little bit of surface rust in places but very limited.

What should I spray down (and also the underside of my patch panel) there once I get rid of that and it's nice and clean? Waxoyl or similar or something else?

I like Ospho for stopping/converting the rust and Waxoil ( lanolin based fluid film/ Woolwax) for coating but welding the fluid film would be risky, I'd think, and you can't paint it. Weld-through primer on Ospho is another way to go.

Thanks. I have enough access now to spray some waxoyl and to let it set before welding. After I weld in this patch I still should have enough access to spray the underside of my repair.

The mild steel sheet I have has some kind of coating on it from the factory. Makes it a hazy grey colour. What is this, Zinc primer or just the way it's finished from the factory? Do I need to remove this finish before applying waxoyl?

If you coat the inside with fluid film before welding, you run the risk of igniting it, which might be exciting...
Your sheet may be galvanized. See if white vinegar or muriatic acid dissolves it. That's very good for rust but you should remove it and spray with weld-through primer where it is going to be welded.
Also, if you apply a creeping fluid film inside the tunnel before painting or seam-sealing, it can wick into and out through the seams and nothing will stick to it. AMHIK....
I'd treat the rust/metal with Ospho and/or paint/primer, then weld, then paint exterior, then coat inside with ff.

Looking at the pics you posted made me check out some things on my own scooter that I'm restoring. Vespas seem to rust in the same places.

Here is my OCD analysis:

Over time the spot welded seams between the floor and tunnel at the rear start to open up because of the flexing from the center stand. Then rust creeps into the seams which weakens the metal and opens up the joint more.

There is really no way to get rust out of those seams without taking them apart. Often not worth ruining perfectly good metal to rip apart seams.

I did a lot of work sandblasting the inside of the tunnel and painting it. The outside of the scooter is now in epoxy primer, but there is still rust between the seams.

I put the scooter on its side and scraped out the seams on the inside with a sharp pick. Then I brushed in Ospho (phosphoric acid). I also soaked some paper towels in Ospho and stuffed them in the seam overnight.

After that, I will clean out the joint (on the inside) apply rust paint, a bead of seam sealer and another layer of epoxy.

Rust can be stopped indefinitely as long as it is sealed and water and oxygen can't get to it. I have stuff on my vw bus like that I did decades ago with no sign of rust.

For your project, I would use weld through primer before you weld the seams together. Do rust treatment and paint AFTER your welding or you will just burn it off.


Treating seams with Ospho.

Seam sealing the outside

Seam sealing the outside.

Thanks. Yes, don't want any exciting moments! Your plan sounds good.

Just got the sand blaster and media. Actually works very well. I may need a new compressor at some point for it.

This has lead me on to more questions. I believe there have been some previous repair attempts on the areas pictured but this also may be a factory finish?

On some of where the floor board meets the tunnel the metal work is completely flat against each other but in other areas is raised and does meet. It looks like some kind of filter or flexible filler in there. I've use my Dremel with a small cutting disc to cut some out. So the question is, is this a factory finish or a bodge at some point?


Not perfectly joined. Bodged or some kind of factory process / finish?

Perefectly joined.

Rust in the seam expanded the joint. Someone may have filled it with something at some point. I can also see pillowing around the spot welds on the tunnel side from rust expansion.

It looks like someone may have put some filler in there. That's exactly what I meant about those seams opening up because of flexing. This is a bad place for filler. Flexible seam sealer would be way better.

There are a couple places on the tunnel that are 3 layers of metal.

One thing I will do is install a reinforcement plate on the bottom and luggage hooks on the top to fix the flexing from the center stand. Otherwise, the seams will just open up again.


Bottom plate

Center stand reinforcement. There are versions with luggage hooks.

3 layers of metal here.

This sounds exactly like mine. Seems over kill to rip up the floor and all the extra work involved if I can stop the rust now and treat it all to stop further rust.

If you look down into the frame you can see where the tunnel runs back to the motor mounts and the rear body overlaps it. You can see how any moisture is channeled down between the two.
Once rust forms, even humidity can keep it growing.

Mine has that too. Once the joint opens up with flexing the rust gets in and pushes it apart more…I think.

I thought about cutting out a thin strip of the the floor on either side of the tunnel flange and welding in a new piece, but I doubt it would put me much further ahead. It took many years to get that way, so with proper rust treatment and sealing I hope it lasts a long time. Worst case scenario, I have to go back and patch it someday.


Rust expansion/flexing of the flange on the right side.

That was the problem mine had. The pillowing.

But it was much worse, and I was afraid it would push the pieces apart.




It's lighter here.

One problem I didn't see until after blasting. The metal on the frame channel was paper thin from rust, and had holes after blasting that needed repair. I was happy I caught these.

I was able to add some metal to the inside with the mig welder, and didn't have to replace the it.

Yeah I think so too but I think they also used flexible seam sealer in other areas of the rear arch and when i pulled it off there was more rust underneath than in other areas so not sure it works that well or perhaps it was just put on wrong. It's wasn't painted over after...

I like the idea of the reenforcment but how will you seal it properly to make sure it doesn't become another water trap?

I completely sandblasted the tunnel and coated it with an antitrust paint. The sandblaster didn't get into the seams, so after the Ospho I will be painting the seams from inside with thinned rust paint followed by a bead of seam sealer.

There's no way to know if the rust is stopped for good other than seeing if it comes back. It's really hit and miss. Sometimes rust comes back even if you rip it all apart and sometimes it doesn't after rust treating what's there. Even if it does, it's usually a lot easier to fix than the first time…when a bike may have sat out in the rain for years with a tunnel full of crud and mouse nests.


Tunnel before

Tunnel after lots of blasting

Painted tunnel

Rusty floorboard

Sandblasting floor.

Thanks for the all the info. Really useful. When you say rust paint do you mean Rustoleum or similar or something else?

I was thinking of just using a few coats of anti rust primer as it contains zinc but maybe that's not enough?

I can't see how you accessed your tunnel, did you cut a hole or do it all from the top?

I accessed the tunnel through the top and through the brake pedal hole. I have long arms and a cheap boroscope camera that works with my phone.

Here is a link to the part of my thread where I cleaned out the tunnel:

That escalated quickly-2 new scoots (Page 2)

Rust removal and welding in tight spaces is kind of my thing as I have been restoring a VW bus for years Same spot welded construction with lots of rust sandwiches to pull apart. I have cobbled together some oddball tools to remove rust.

I used a product called master series silver for painting the inside. I think it's a silvery zinc rich paint that is used on bridges. I think any kind of rust paint on the inside is fine with good surface prep.

Here is a link. If it's not available in your location I'm sure you could find something similar:

https://shop.masterseriesct.com/

I think the best thing you can do for any vehicle is to drive it often and look after it. Nothing falls apart like a car or bike left unused out in the weather or a damp corner of a shed. Lots of people here just spot treat their bikes as part of the upkeep and ride on.

Thanks, yeah I picked up some Hammerite rust paint in a spray can today and started the rust removal with phosphoric acid.

Have found a fair few more spots of rust that have made it through the floor board with paper thin metal surrounding it. I'm going to have to cut a inch or so each way to find decent metal to weld to. I need to asses it again tomorrow once I've made those cuts to see how much worked I've got to patch this floor up vs getting a replacment panel.

Finding too many of these holes now with thin metal around. I'm up to about 5 all in different places. Looking more likely I'll replace the floor to make the job good. Will actually be better and less time consuming than trying to save it now.

Surprising what sand blasting and rust removal chemicals can reveal! I think I'm going to struggle to patch this up satisfactorily with the paper thin metal along the seams. I'd end up cutting up the majority of the floor! Previous bodge repairs have not helped.

It was worth a try finding out what was worth saving, but yeah doing that floor section would probably be easier in the long run and would allow you access to the tunnel for any small repairs and rust treatment.

Yeah it was getting a little too much to save sensibly. I'll weld it myself so for the sake of £100 it makes the most sense.

When you cut it out, remove the three sections leaving the welded strips, drill the spots and peel them off. This is way easier than trying to remove the whole panel.

I had to cut a slot along the inside of the bead to adjust it to fit the width.