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1Back to top Go down   Plastic welding or glue?? Empty Plastic welding or glue?? Sat Jul 09, 2022 9:44 pm

MartinW

MartinW
Life time member
Life time member
SSD's (Paul) LT 100's plastic dash panel has significant cracks in it. We tried a few different glues to stick it together, Super Glue 2 brands, Bondic, and 5 min Araldite none of them worked. After he left I remembered that I had a tin of blue plumbers glue. Would that of worked? Does anyone know what type of plastic the dash is made of so we can use the correct filler rod if we decide to weld it together? It is part number 2 in the drawing. I've also been looking at a hot plastic staple gun has anybody used one? The finished look is irrelevant as when the glue failed I used deck tape. This really looked good but due to flexing it started to lift after a week or so.
Regards Martin.
Plastic welding or glue?? Lt_k1010


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K75s Hybrid
    

2Back to top Go down   Plastic welding or glue?? Empty Plastic welding or glue Sat Jul 09, 2022 10:22 pm

daveyson

daveyson
Life time member
Life time member
Maybe plastic welding and glue. 

I used to do plastic welding for a commercial playground company, but that panel is so thin and brittle that I swear it cracked on me once just cause I looked at it cross-eyed.

One option to toy with is weld it and glue a thicker piece of plastic on the back with a good surface area to beef it up a bit.


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11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

3Back to top Go down   Plastic welding or glue?? Empty Re: Plastic welding or glue?? Sat Jul 09, 2022 11:31 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
I had the same problem with cracks in that piece that is below the windshield on my RT.  It was too thin to try welding or gluing.

What worked for me and has lasted for 5 years now is laminating a patch on the back side.  The panel is made of ABS plastic so I used some thickened cement for ABS plumbing.  There are two types of cement for these fittings, the regular that is clear and the stuff that is black and thicker.  I think it has ABS plastic dissolved in it.

I reinforced the repair with small pieces of fiberglass window screen.  Cut the patch to cover the crack and extend about 3/4 inch on each side and beyond the end of the crack.

I started by gluing the crack with Super Glue, applying it along the crack from the rear of the part.  Be careful to get the glue just on the crack.  Then scuff the area around the crack with fine sand paper. This helps the solvent in the cement soften and chemically bond with the part's surface.

Apply a film of the ABS cement around the crack going about 1" on each side of the crack and put the patch in place gently pressing it into the cement.  It takes a couple minutes for the cement to harden so you might need to press the patch into the cement if it lifts up.  When the cement is almost cured but hard enough to hold the patch in place put another thin coat of cement on the patch.  Repeat a couple times until the screen is covered but still visible in the cement.

Set the repair aside to cure overnight and then reinstall on the bike.


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Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

4Back to top Go down   Plastic welding or glue?? Empty Re: Plastic welding or glue?? Sun Jul 10, 2022 12:19 am

MartinW

MartinW
Life time member
Life time member
Thanks fellas I've just got off the phone to SSD I'll probably go down Gryphs path and then cover the evidence of the repair with deck tape.
Regards Martin.


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K75s Hybrid
    

5Back to top Go down   Plastic welding or glue?? Empty Re: Plastic welding or glue?? Sun Jul 10, 2022 12:42 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Martin, there's no need to cover the evidence, the patch is on the rear of the part.  Al you can see from the front is the hairline of the crack.  Be careful with the super glue and the repair is virtually invisible from the front.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

6Back to top Go down   Plastic welding or glue?? Empty Re: Plastic welding or glue?? Sun Jul 10, 2022 12:44 am

MartinW

MartinW
Life time member
Life time member
Plastic welding or glue?? 112350


__________________________________________________
K75s Hybrid
    

7Back to top Go down   Plastic welding or glue?? Empty plastic welding or glue Sun Jul 10, 2022 2:05 am

redrockmania

redrockmania
Silver member
Silver member
If you are unable to identify the type of plastic needing repair, one way to test if the plastic can be welded is to get a small sliver of the plastic and attempt to plastic weld it to the same type of plastic. Either it will melt and fuse or not respond to heat other than to catch fire or show no signs of liquifying. One way I have done successful repairs to plastic and fibreglass panels is to use a piece of thin sheet aluminium with fine holes in it as the support for the repair. I repurposed some aluminium sheeting of this type I had purchased to make a leaf guard on my house roof gutter. The aluminium is easily bent into shape and the small holes (to allow water flow) provide an excellent rough surface for your bonding glue to adhere to.

    

8Back to top Go down   Plastic welding or glue?? Empty Re: Plastic welding or glue?? Sun Jul 10, 2022 6:59 am

Dai

Dai
Life time member
Life time member
daveyson wrote:One option to toy with is weld it and glue a thicker piece of plastic on the back with a good surface area to beef it up a bit.
Not an option, unfortunately. It will stop the dash from seating in the fairing. Got the t-shirt. It cost me £64 from Motorworks.


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1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

9Back to top Go down   Plastic welding or glue?? Empty Re: Plastic welding or glue?? Sun Jul 10, 2022 9:42 am

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Dai wrote:
daveyson wrote:One option to toy with is weld it and glue a thicker piece of plastic on the back with a good surface area to beef it up a bit.
Not an option, unfortunately. It will stop the dash from seating in the fairing. Got the t-shirt. It cost me £64 from Motorworks.
That is why I had to do my repair as I described above.  By using the fiberglass screen, it's possible to carefully sand the patch to remove any high spots that interfere with installing the part.

It boggles the mind that Motorrad decided to use such a flimsy piece of plastic on that boat anchor of a fairing to save a little weight.


__________________________________________________
Present:
1994 K75RT
1991 K100RS


Past:
1988 K100RS SE
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

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