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Author Topic: Plastic Welding  (Read 291 times)

Offline Bob_Roller

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Plastic Welding
« on: November 04, 2022, 09:38:31 AM »
My '87 Guzzi has a plastic rear fender and has numerous cracks .
Part no longer available, I've got a Moto Guzzi salvage shop looking for a replacement part I contacted them 6 months ago and check in about every month to see if a part has been found, up to today no luck .
From what I've been able to research, only about 125-150 of these bikes were imported into the US .
Can't ride the bike, the rear turn signals come loose in about 20 minutes of riding and hang from the wires . :furious3:
So now I'm going to try plastic welding and then reinforce the underside of the fender with fiberglass cloth .
Tried welding plastic at work, had some damaged parts where the ultrasonic welds broke .
First attempt not so great, it held, but looked pretty lousy !!!
Found a plastic welding tool from Harbor Freight a tool store with most products made in China, as one member from AU said about this type of store, ' cheaper than chips ' type tools !!!


https://www.harborfreight.com/80-watt-iron-plastic-welding-kit-60662.html

I start my annual 7 week vacation on Nov. 10, I'll remove the fender and have a go at it .
'81 R65
'82 R65 LS ?
'84 R65 LS
'87 Moto Guzzi V65 Lario
'02 R1150R
Riding all year long since 1993 .
I'll give up my R65, when they pry my cold dead hands from the handlebars !!!!!

Offline Justin B.

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Re: Plastic Welding
« Reply #1 on: November 04, 2022, 11:36:02 AM »
I bought one of them years ago but have never used it.  I had read up on the process and IIRC the consensus was that they would do a good job if you could use the same material for filler as the item you are repairing.
Justin B.

2004 BMW R1150RT
1981 R100RT - Summer bike, NEKKID!!!

Offline Bob_Roller

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Re: Plastic Welding
« Reply #2 on: November 04, 2022, 11:44:28 AM »
That was a bit of a concern, not knowing what the fender was made of .
I'm going to try black ty-wraps as a filler .
'81 R65
'82 R65 LS ?
'84 R65 LS
'87 Moto Guzzi V65 Lario
'02 R1150R
Riding all year long since 1993 .
I'll give up my R65, when they pry my cold dead hands from the handlebars !!!!!

Offline georgesgiralt

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Re: Plastic Welding
« Reply #3 on: November 05, 2022, 02:50:14 AM »
Hello,
A friend of mine had success repairing a fender (Honda bike).
He put a strip of aluminum on the tire side welded in place with epoxy and fiberglass cloth. He then drilled the needed holes and painted the whole thing black using bumper paint.As far as I know, the fender is still in place and doing it's job....
It is a bit ugly in the inside, but you are not supposed to look under the skirt of the old lady.....

Offline dogshome

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Re: Plastic Welding
« Reply #4 on: November 05, 2022, 03:52:24 AM »
I've done this on panniers very wrong, then almost right. You must use the exact same plastic. If you get a mixed small sample bag from a supplier, you soon find out.

If it's valuable, I might take it to a car body shop. They do this all the time on bumpers.

Practice on a scrap plastic, it's much like ordinary welding. Right temperature, speed and feed.
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline Bob_Roller

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Re: Plastic Welding
« Reply #5 on: November 16, 2022, 01:15:21 PM »
Did a local search for a shop that does plastic welding .
Found one 5 miles from home .
Just took the fender in and was told the plastic was an uncommon material and if I tried to weld it without the same filler rod, it probably would have failed within a year or so .
I told them I wanted to put fiberglass cloth on the inside after being repaired, was told most likely the fiberglass repair would not adhere to the plastic .
So I'm having this shop do the plastic repair for $50 cash should be done next week .
'81 R65
'82 R65 LS ?
'84 R65 LS
'87 Moto Guzzi V65 Lario
'02 R1150R
Riding all year long since 1993 .
I'll give up my R65, when they pry my cold dead hands from the handlebars !!!!!

Offline Bob_Roller

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Re: Plastic Welding
« Reply #6 on: November 17, 2022, 12:14:32 PM »
Got a call this morning, the fender was done .
I picked it up and I don't think it will crack again .
Against their advice, I'm going to reinforce the fender on the underside with fiberglass cloth and epoxy .
'81 R65
'82 R65 LS ?
'84 R65 LS
'87 Moto Guzzi V65 Lario
'02 R1150R
Riding all year long since 1993 .
I'll give up my R65, when they pry my cold dead hands from the handlebars !!!!!

Offline dogshome

  • Lives in Foothills of Mt. Olympus
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Re: Plastic Welding
« Reply #7 on: November 17, 2022, 12:57:03 PM »
Ancient and wise Master Yoda: "adhere plastic, it won't"
Plucky young Skywalker "I'm doing it anyway".

Use the force Bob, you'll need it  :ROTFLMAO:
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O

Offline Bob_Roller

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Re: Plastic Welding
« Reply #8 on: November 17, 2022, 01:13:54 PM »
To add a little bit, the previous owner put large area washers on the underside and back of the fender, he used some epoxy .
I've had the bike going on 14 years and the washers are still on there, no idea when he did this repair .
I got the bike in 2009, the previous owner parked the bike in 2006, due to not passing exhaust emissions testing that required here for annual vehicle registration process .
What he didn't know, was that if you had collector vehicle insurance and historic vehicle license plate, you were exempt from emissions testing .
I didn't inform him of this !!
Him and his wife were being evicted, so I don't think he would have kept the bike, he had 10 others to get rid of as well .
'81 R65
'82 R65 LS ?
'84 R65 LS
'87 Moto Guzzi V65 Lario
'02 R1150R
Riding all year long since 1993 .
I'll give up my R65, when they pry my cold dead hands from the handlebars !!!!!

Offline dogshome

  • Lives in Foothills of Mt. Olympus
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  • Posts: 126
Re: Plastic Welding
« Reply #9 on: November 17, 2022, 01:36:41 PM »
I Glued the swirl flap plugs in the intake manifold of my car some 5 years ago with Devcon epoxy. 100C to -5C, +30PSI to -10 or so and they haven't moved. If the bumper place has welded using the same plastic as the bumper, that should do it. Please report back in 15 years if when the epoxy falls off  8)

Got any pics of the welding?
肉(r?u)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
* Literally: To hit a dog with a meat-bun.:-O