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My recently acquired '79 GS850 has Vetter bags and a "Plexifairing" which appear to have been installed about the time the bike was purchased.
The windscreen is a large clear plexi 1/2-fairing which is molded to provide space for the levers & bars and wraps in front of the instrument pod. Likely everyone else on this forum is familiar with these screens....
The screen is in good shape and clear excepting for some deep scratches across the leading edge of the bulge for handle bar/lever clearance. These look to be the results of some decades of mis-judging garage door openings and other obstructions. (VBG) Having been guilty of those sorts of offences many, many times I assume....
In case someone else may profit from the description, here is how I removed the scratches to produce an almost new fairing:
Hair dryer was used to heat and peel off the two Plexifairing decals in hopes that they will be able to be reinstalled. I'm planning to detail the bike up to as nice a condition as possible without expending any real money. Translation: "It won't be a high value classic even if concours restored and my Welsh heritage encourages guarding of my money."
I used 400 grit wet & dry paper which was frequently washed in a pail of water to remove material down to the base of the scratches.
*Note* the experienced body shop people here will (hopefully) correct any errors in what I am attempting to convey. Sanding is deceptive in that one can turn things into a mess in short order or, conversely, spend a lot of time and effort without useful result.
Plastics and especially clear ones need to be treated with some consideration as there are a number of problems inherent which are less evident in finishing metals and wood. Plastics melt at a much lower temperature than metals and so can discolor or embed with sanding particles so as to produce a poor quality surface. One must take care when using power tools or even by hand in order to avoid over heating the surface. These are two of the reasons for which I like to wet sand plastics: avoid heating and discourage sanding particles from embeding.
Too coarse a paper introduces scratches and even stress areas into the plastic while too fine a paper simply polishes the irregularities producing a surface which often looks worse than the "before".
400 grit removed the scratches and was followed by 800 grit for a few passes, 1,000 grit, then 1,500 grit. By now the fairing surface was looking almost good enough along both sides and could have been left that way with a great improvement however the surface as not as crystal as ideal so a soft pad was chucked in a cordless drill and used with Auto Glym Body SHop Glass Cleaner 06B to finish polish. Note that his product is not specified for use with plastics but seems to work beautifully (if a word) for finishing plexi windscreens. I have also used this process in order to refinish the surfaces of old signal and brake light lenses. It also works on plastic headlight lenses although one should try a small area first.
These old, heavy guage plexiglass wind screens are often discolored or "frosted" due to abrasion, sun damage or years of impact by tiny road particles such that the plastic appears to be damaged through the thickness. On surface cleaning, however, it is often seen that the damage was limited to a thin surface layer which was easily removed by light sanding/polishing.
Hope this is useful to someone....oh, almost forgot...the same goes for glass headlight lenses. After many years the glass often becomes "sand blasted" by road particles which can be refinished by polishing the glass.
Hope this is useful to someone,
Norm
The windscreen is a large clear plexi 1/2-fairing which is molded to provide space for the levers & bars and wraps in front of the instrument pod. Likely everyone else on this forum is familiar with these screens....
The screen is in good shape and clear excepting for some deep scratches across the leading edge of the bulge for handle bar/lever clearance. These look to be the results of some decades of mis-judging garage door openings and other obstructions. (VBG) Having been guilty of those sorts of offences many, many times I assume....
In case someone else may profit from the description, here is how I removed the scratches to produce an almost new fairing:
Hair dryer was used to heat and peel off the two Plexifairing decals in hopes that they will be able to be reinstalled. I'm planning to detail the bike up to as nice a condition as possible without expending any real money. Translation: "It won't be a high value classic even if concours restored and my Welsh heritage encourages guarding of my money."
I used 400 grit wet & dry paper which was frequently washed in a pail of water to remove material down to the base of the scratches.
*Note* the experienced body shop people here will (hopefully) correct any errors in what I am attempting to convey. Sanding is deceptive in that one can turn things into a mess in short order or, conversely, spend a lot of time and effort without useful result.
Plastics and especially clear ones need to be treated with some consideration as there are a number of problems inherent which are less evident in finishing metals and wood. Plastics melt at a much lower temperature than metals and so can discolor or embed with sanding particles so as to produce a poor quality surface. One must take care when using power tools or even by hand in order to avoid over heating the surface. These are two of the reasons for which I like to wet sand plastics: avoid heating and discourage sanding particles from embeding.
Too coarse a paper introduces scratches and even stress areas into the plastic while too fine a paper simply polishes the irregularities producing a surface which often looks worse than the "before".
400 grit removed the scratches and was followed by 800 grit for a few passes, 1,000 grit, then 1,500 grit. By now the fairing surface was looking almost good enough along both sides and could have been left that way with a great improvement however the surface as not as crystal as ideal so a soft pad was chucked in a cordless drill and used with Auto Glym Body SHop Glass Cleaner 06B to finish polish. Note that his product is not specified for use with plastics but seems to work beautifully (if a word) for finishing plexi windscreens. I have also used this process in order to refinish the surfaces of old signal and brake light lenses. It also works on plastic headlight lenses although one should try a small area first.
These old, heavy guage plexiglass wind screens are often discolored or "frosted" due to abrasion, sun damage or years of impact by tiny road particles such that the plastic appears to be damaged through the thickness. On surface cleaning, however, it is often seen that the damage was limited to a thin surface layer which was easily removed by light sanding/polishing.
Hope this is useful to someone....oh, almost forgot...the same goes for glass headlight lenses. After many years the glass often becomes "sand blasted" by road particles which can be refinished by polishing the glass.
Hope this is useful to someone,
Norm
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