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Discussion Starter · #1 ·
I've read every thread about plastic modification, but i'd like to hear what you may think about my options. keep in mind my experience with body modification is zero.

my bike:



I want to cut my subframe a bit, really just do a bit of trimming. what i'd like to do is cut my tail piece to make it slightly shorter and angled so it's taller. so how i should rejoin the plastics is question number one. Should buy a plastic welder? should i use epoxy and fiberglass? what's the easiest? what will create the best hold?

question number two: after the tail is formed, i would then have to put a "top" on to fill in the void created by the missing rear seat. i don't need it to open and close. i just need the "hole" covered. how would you go about filling the void? create a mold with foam?
 

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Flip-Flop King
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167 Posts
Buy a seat cowl.

As for joining the plastic, obviously a plastic welder is the best option, but if the budget is below the "enormous" level then use a soldering iron. Read up on plastic welding with one of those.
 

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Discussion Starter · #3 ·
well, the tail will be so short and angled that a seat cowl isn't an option. i think the only option is to make the top.


and yeah i am reading up on plastic welding. doesn't seem TOO difficult.




edit: btw, are you on clubsi?
 

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Function IS Form
19 Z900, 88 Kat11
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17,434 Posts
Fiberglass would be stronger. Plastic welding would be easier once you get the hang of it.

Making a cowl/top piece would be good practice for lost-foam fiberglassing.
Cut foam into a mold. Lay bondo over it to prevent the fiberglass resin from melting it.
The hard part is getting the mold in correct proportions but a tail cowl would be the easiest practice.

Any questions? :D
 

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hack
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729 Posts
plastic welders are cheap. you can get one for like $30. try searching for "kayak welding" its ugly when you're done though. nothing bondo cant fix. then glass the seat hole. learn everything at once
 

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Good stuff. You're a step ahead of me Andrew. I've been doing a lot of thinking about shortening the subframe and tail lately. Don't know when I'll be able to get to it though. I look foward to seeing what you put together.
 

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Soldering irons suck for every ABS component i've ever tried it on - and I've heard so do the soldering iron style plastic welders -but I dont know first hand because i've never used one of those.

I bought an airless welder kit for like 140 off ebay and its awesome and came with all sorts of different tips and rods for pretty much any plastic you can think of. Works great, and came with instructional video too. I beleive its same as this kit here http://cgi.ebay.com/ebaymotors/Uret...011QQitemZ320140415722QQrdZ1QQsspagenameZWDVW

Think of it this way - you can weld some 16ga mild steel with oxy or a cheap arc welder, but would you try to weld 1/4" steel with one? Or would you use a 220v mig or something? Same with plastic, while you might repair some polypropylene or polyethylene 1/8" kayak with a soldering iron, it probably isnt going to work too well on a 1/8" or thicke piece of ABS. Thermoset and thermoform plastics are totally different too - and there are TONS of variations of say ABS for example - not all ABS is equal, all sorts of plasticizers and additives can be used when its created to give it different properties.

So use the right tool for the job.

Fiberglass works to repair plasitc to an extent, if you prepare the surfaces right it will work decent. But eventually it fails when you do it on bikes, because of vibrations and all the flexing from removing and reinstalling panels. At least thats my personal experience and also the opinion of every professional autobody shop i talked to before i purchased my plastic welder...

Fiberglass would be great for the cowl, +1 on the foam/bondo plug.

Also, you could mofifiy a seat cowl by cutting it up and using the plastic welder to rejoin it so it fits your seat, but honestly thats a PITA and more work than making it out of glass.
 

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Eff Tee Pee
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+1 my 600rr had some f.glassin to hold a clean break in the tail. however when i took the tail off i could see it was barely holding it. i've since plastic welded it and that section is very strong now.

i agree on using the right tool for the job. beats doing it twice the wrong way.

if you have any more questions about plastic welding....i've done a pretty decent amount of it and have gotten good.

airless plastic welder is correct! (texas instruments or something makes one)
 
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