Nut under my seat pin/bolt broke. What would you do?
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Enthusiast
P 125x "Il Ratto"
Joined: 22 Apr 2013
Posts: 72
Location: Madison Wississippi
Wed May 01, 2013 3:59 pm quote
Not sure if this is a common prob but I just had the nut under my seat pin/bolt came loose.

I am sure you all know its tack welded to the inside of the frame at 3 opposing corners.

I am thinking the mouse commune that sprung up inside the frame during its 20 year hibernation created the moisture (breath vapor, piss, honta virus, etc.) required to rust the bolt to the nut stronger than the welding.

Normally it would be no big deal. I would just reach under there and hold the nut with a wrench while I tightened the bolt on top.

The rub is that I have a rack that is held down by that seat post bolt.

You can't get the tank out with the bracket on and you can't get the bracket off unless you are able to reach in and hold the nut.

Get my problem?

I don't see how it would be possible to reweld it.

Any ideas?

For the time being I am just going to rock it sans bracket/rack but eventually I would like to get it back to how it is supposed to be.
Addicted
'79 P200, '74 VBC Super, '80 100 Sport
Joined: 23 Jan 2012
Posts: 712
Location: 32 37' 40" N, 117 2' 53" W
Wed May 01, 2013 4:17 pm quote
seat bolt
what kind of rack, have a picture of the bracket?
nothing at all
Joined: 14 Nov 2008
Posts: 9657
Location: westla
Wed May 01, 2013 4:54 pm quote
Your'e gonna have to be smarter than your average bear.

Get your wrench that fits the bracket bolt.
Get a wonder bar or big flat tip screwdriver.

Start turning the bolt loose and at the same time slip the tip(yea i said it)under the bolt head and force up as you loosen./or tighten.

The idea is the pressure of the nut underneath is enough to hold it in place-ish.

By the way, if yor seat dick is loose than everytime your seat moves you are putting stress on the welded nut, which is what leads to weld break.

Good luck!!

(you also need to include info on bike type, location, favorite food, bed time.......)

Generally speaking the tank bolts that hold rack brackets are not nutted but back threaded.
Enthusiast
P 125x "Il Ratto"
Joined: 22 Apr 2013
Posts: 72
Location: Madison Wississippi
Wed May 01, 2013 5:05 pm quote
I already got the seat bolt off.

I tried that prying method. No dice.

I actually had to use a dremel cut off wheel to make a slit in the bracket. I got it thin enough that I could bend the bracket and get the tank out.

Once I had the tank out I put a wrench under there (on the nut that had broken its welds) and a wrench on the seat bolt.

The bolt was actually so rust welded that it snapped in two rather than the nut letting loose. And that was after a PB blaster soak.

Had I known what it looked like under there I would have just hacked the seat bolt off.

Anyway I welded the bracket/plate thing back where I thinned it and its all good.


The bracket is used to hold on what I believe is called a "BBQ rack". Its this thick chrome steel plate with bolt holes for the back 2 tank bolts, the seat bolt, and 2 square holes in the back.

So the issue isn't getting it off.

The issue is what do I do now that the nut is loose.

I can't just put another nut under there because with the metal bracket I can't pull the tank out which I would need to do to hold the once welded nut in order to remove the seat post that I would need to remove to get the bracket off.

Its a catch 22.

The advice I am looking for is what to do about securing a nut or some other fastener where the nut was previously welded.
Enthusiast
P 125x "Il Ratto"
Joined: 22 Apr 2013
Posts: 72
Location: Madison Wississippi
Wed May 01, 2013 5:08 pm quote
Oh and its a P125x in case that makes a difference.
nothing at all
Joined: 14 Nov 2008
Posts: 9657
Location: westla
Wed May 01, 2013 5:12 pm quote
You said you have a welder......so why not weld the seat dick nut back in place??
Enthusiast
P 125x "Il Ratto"
Joined: 22 Apr 2013
Posts: 72
Location: Madison Wississippi
Wed May 01, 2013 5:32 pm quote
I can't maneuver it in there or see what/where everything is.

I tried to get it to happen by putting a magnet on top and maneuvering the nut underneath to the right spot but I couldn't make it happen. The shape of my welder doesn't allow it and even if it did I can't see up in there. I would probably end up melting a holes or holes in the frame.

I am guessing these had to have been welded on when the frame was in pieces. I could be wrong but I am not sure how else it could have been done.

P.S. "seat dick" is a totally apt description.
Addicted
1980 P200e, 1956 ACMA, 1979 P200e, 1974 Ciao
Joined: 04 Jun 2009
Posts: 766
Location: Ithaca, NY
Wed May 01, 2013 6:14 pm quote
I've got exactly the same problem. I tried tack welding the nut back into place with my MIG, but couldn't get a good weld, because of the location.

I eventually punted on that, and used JB-Weld. Just be VERY careful if you do that, so as not to glue your seat post to the nut in the process!

It probably won't hold up for long, but at least I'm able to take the bolt on and off.

The other thing I've done in this circumstance is to duct-tape the nut in position before buttoning up the tank and rear rack. The duct tape will hold the nut in place long enough to get the acorn nut started, then just pull up on the acorn nut as you tighten it You can't get it very snug, but that bolt isn't really holding anything together anyway. I did that all last season.

Hojo
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6952
Location: Victoria, Australia
Wed May 01, 2013 7:27 pm quote
You can buy a nut that's already captive.... I'd drill some holes from above, hold the new captive nut in position and 'spot' weld from the top.

nothing at all
Joined: 14 Nov 2008
Posts: 9657
Location: westla
Wed May 01, 2013 7:55 pm quote
You can not spot weld from one point. You need to "pinch" material to spot weld.

You must be meanin tack weld.

I would just jb weld it and move on.
Member
Vespa 1965 50N
Joined: 28 Apr 2013
Posts: 18
Location: Montreal
Wed May 01, 2013 8:04 pm quote
If you cant weld it from the inside spot weld the nut from the outside. Drill small holes around where u want the nut to be welded n tack the nut in place from the other side filling the drill holes with ur tack weld, im no pro welder but the small spot welds then can be ground down n your nuts r in place lol, nuts in place get it lol
Enthusiast
P 125x "Il Ratto"
Joined: 22 Apr 2013
Posts: 72
Location: Madison Wississippi
Wed May 01, 2013 8:07 pm quote
Maybe I could get a captured nut and use some of my patented JB rebar and just slather it on there. If I could get one with some decent sized wings on it that would up the surface area by a lot.

Not ideal but yeah.

The other option I have considered was just straight up welding the top half of the "seat dick" to the bracket and thus totally eliminate the nut underneath.

It would be pretty ghetto though. '

Then again it would be all under the seat so no one would know but me.
nothing at all
Joined: 14 Nov 2008
Posts: 9657
Location: westla
Wed May 01, 2013 8:09 pm quote
No no no no

Metals shop 101

spotweld.jpg
spot weld

tackweld.jpg
tack weld

nothing at all
Joined: 14 Nov 2008
Posts: 9657
Location: westla
Wed May 01, 2013 8:32 pm quote
Oh, one more suggestion.

Stay away from the captive nuts.

Go for whats called a 'weld nut' in a metric size.

Much more suited for 'spot weld' 'tack weld' or jb weld.

As a matter of fact, a little smear of jbweld with a 'weld nut' and this thread will done.

Or we can add it to the 'quick fixes' thread.

weld nut.jpg

Addicted
Vespa PX200
Joined: 22 Jun 2010
Posts: 621
Location: Sydney, Australia
Wed May 01, 2013 10:41 pm quote
You need to plug weld it in place (plug welding is a commonplace welding technique in industrial structure steelwork as well as autobody work). You can access the underside just not to be able to weld from the underside. Place a nut over the hole. Drill 3 small holes around the hole adjacent to the peak of 3 hex'es. Here's the cool part. Get an allen bolt the same thread as the nut. Make sure the threads are clean and undamaged so the nut spins down easy. Reach under with the nut and start the allen bolt from above. Turn the nut so the hex peaks can be seen through three holes you drilled. Tighten the allen bolt just enough to hold the nut in position. Tig weld the hex peaks to the sheet metal then fill the plug (the hole) with filler rod. The key to this working is the use of an allen bolt. its head being smaller than the effective of the equivalent hex head.

Takes longer to write it up than to do it, but allows me to draw on years of writing eng specs & procedures for pwr station construction.

Alternatively, if you can't be arsed doing this and dont want to deal with burning duco just get a nutsert.

Plug Weld Blind Nut.jpg

Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6952
Location: Victoria, Australia
Thu May 02, 2013 1:05 am quote
jimmyb865 wrote:
You can not spot weld from one point. You need to "pinch" material to spot weld.

You must be meanin tack weld.

I would just jb weld it and move on.
That's why I said "spot" weld by drilling holes and welding from above... like they have done here in the pic below.

JB is enough to hold it in place but once you flex the area or put any lateral force on it, it'll break away.



The weld nut looks like a permanent solution, maybe a lttle less fiddly than TCC's method... which I'm sure would be good too.
Veni, Vidi, Posti
'80 P200E, '76 Primavera 125 ET3. '59 Vespa 150
Joined: 30 Apr 2007
Posts: 6851
Location: GT, Texas
Thu May 02, 2013 2:44 am quote
Shitload of JB weld worked for me.
Molto Verboso
Joined: 31 May 2009
Posts: 1220
Location: NC, USA
Thu May 02, 2013 4:13 am quote
I like jimmyb's weld nut with jb weld idea for ease of use and not burning off paint. Thanks.

A variation of TCC's method, which works and holds great.

If paint burning is no problem, SLIGHTLY enlarge the hole. Hold the nut from underneath, screw a long enough bolt into it, and hold it up against the body with the welder ground clamp on the bolt head. Lightly tack weld at the edge of the slightly enlarged hole. Use something to keep splatter off the bolt threads, or use something non-threaded or non-ferrous to hold the nut against the body.

A good welder (not me), can tack without much paint melting or welding the bolt to the nut. The seat pin will hide most of the uglicity.
Lurker
'67 VBC Large frame with sidecar
Joined: 25 Jul 2018
Posts: 1
Location: NOVA / DC
Wed Jul 25, 2018 3:23 pm quote
Replace stripped nuts with bolts from bottom up
Hey guys,
I'm a total nube to Vespas or any motorcycle - I recently bought an old '67 with sidecar. I ran into the same problem with the nuts under the seat stripping. I took a different approach that ended up (so far) saving me a lot of time and money.

I drilled the holes out just a hair larger (standard was between the metric sized bolts) and used wing bolts like in this first pic to push up through the bottom. I then used a C-clip on top of a washer on each to prevent them from falling back down. Wing bolts were necessary to catch the interior wall while tightening/loosening. One wing bolt had wings too small to catch so I had to try a few different kinds.

I haven't had any negative results from this method so far and if I strip a bolt, I can just pop a new one in.

IMG_1272.jpg
Standard sized wing bolt was in between the stripped metric size and the next metric size up. Deez nuts were still welded in place, and I wanted to drill out as little as possible.

IMG_1273.jpg
Choose wing bolts with large enough wings so they catch the interior wall and don't slip while tightening. Also consider the length: will you have appropriate clearance for the seat to slip the nut on? Is the bolt too long that it will dig into the seat w

Member
1975 125 Primavera +
Joined: 23 Nov 2011
Posts: 28
Location: Los Angeles
Mon Mar 18, 2019 8:55 pm quote
Does anybody know the thread pitch/size of the small frame seat latch bolt?

I have a thread checker kit and I can't find a match in metric or SAE.

I too have a missing nut, bought a new seat latch bolt and need to find a way to get it back together on the frame.
Molto Verboso
Joined: 24 Jan 2008
Posts: 1907
Location: Santa Margarita,Ca.
Mon Mar 18, 2019 11:35 pm quote
Same as seat bolt i believe. m7x1.00
Member
2005 GT 200L, 1978 P200E, 2010 S50 4V, 1966 Blue Badge (Polini), 1965 90 (Malossi)
Joined: 10 Aug 2011
Posts: 16
Location: Huntington Woods, MI
Tue Mar 19, 2019 10:28 am quote
I have the same problem on one of my small frames. I found a solution in the form of a rivet nut, but there are no M7 sized. Ugh.
Member
1970 Rally 180
Joined: 29 Jun 2009
Posts: 19
Location: Northwest USA
Sun Jun 30, 2019 9:22 pm quote
I have the same problem on my 1972 Rally 180. I have devised a fix that will make a sturdy welded solution a possibility, with an alternative fix using super strong rare-earth magnets. I will post pictures when I get it made: simple design, but too hard to describe. Does anyone know if they make weld nuts in the correct size? Isnt it M7x1.0?
Hooked
58 VB1T, 81 100 Sport
Joined: 06 May 2019
Posts: 104
Location: Long Beach, CA
Sun Jun 30, 2019 10:54 pm quote
Same problem on my old P200. Rear tank hold down nut. JB weld-lots!! Held tight for as long as I had the scoot, 15 years. I cleaned the underside of frame extremely well with thinner. Sanded it rough. cleaned again. Use the bolt to attach the nut tight, and pile on the JB.

As others have said, it can flex and break free. For this reason welding is the most secure solution. However, the JB worked well for me as I did not want to burn any paint. Just my experience.
Hooked
P125x (P200 Motor)
Joined: 06 May 2019
Posts: 159
Location: Alexandria, VA
Mon Jul 01, 2019 4:13 am quote
Rivnut:


rivet_nut_tool_rivnut_1457364438_28d29906.jpg

rivet_nut_tool_rivnut_1457364439_66317c08.jpg

Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3708
Location: San Diego, CA
Mon Jul 01, 2019 7:07 am quote
rivnut for the win.

see mine done in this thread:
Pickelhaube
Molto Verboso
Joined: 26 Oct 2015
Posts: 1572

Sat Jul 13, 2019 7:36 pm quote
Last week the threads in the pickelhaube nut stripped out (as opposed to the spot weld failing). I happened to have had the correct sized Time-sert in my shop already, so it was an easy fix.

8C5A0E9E-C1AE-4DC8-AD2B-F0A706F76A78.jpeg

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