Restoring plastic fuel tank from an 80's Kaw

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1/31/2020 2:08 PM

Picked up a mid 80's KDX fuel tank to restore. I've successfully brought back red, yellow and white plastic fuel tanks but this one has me stumped. The green plastic is very dark and has spots of black on it. Underneath you can see the correct color. Sanding with 320 wet/dry paper for 15 minutes did almost nothing. Scraping with a razor blade yields a slight improvement but not the kind I have seen with other colors of plastics. The white areas are where I was sanding.

Is this thing beyond hope or is there a trick to bring this tank back?













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1/31/2020 3:52 PM

I started with a sos pad when I was washing the bike, then hit it with motul shine and go

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1/31/2020 4:04 PM

I have started with worse. I razor blade them first in extreme cases like this. Draw it toward you at a 45 degree angle.

Lot's of elbow grease but it will get you down to a surface that you can start sanding (wet!) and step up from rough (220) to 2000. Good luck!

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2/4/2020 5:39 AM

I got my a Kx tank back from the dead. I used an orbital sander.. Started with 150. Be careful you can remove slot on the corners. Keep stepping down . Finally wet sanding by hand. I cut circles from flat sheets of paper and spray glued each layer to the sander. It saved hours of hand sanding
The final shine came from a buffing disc in a cordless drill on slow
That tank can look new again

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2/4/2020 6:50 AM
Edited Date/Time: 2/4/2020 6:53 AM

Yes it can be done! Prior to the roached '89 KX250 tank in the first image below, I had only done some yellow '74 Yamaha MX100 fenders and those were really simple in comparison! This '89 KX250 tank was a different story and took a lot more elbow grease to remove several coats of bbq black and lots of oxidation and scratches! Just keep at it with the razor bade, I prefer to use it at a 90 degree angle to keep from adding any new gouges. Your tank seems to have some existing deep scratches in it, so be careful trying to chase those too far as the plastic will start to become translucent if you take away too much material. My tank had a deep scratch on one side and I decided it was too deep to try and remove. Once you get the discolored areas cleaned up with the razor blade, you may want to start a little heavier than 320, like a 220 wet/dry to remove the razor blade marks. After that, then move back up to 320 through 2000+. I can't seem to find the website anymore, maybe it was on eBay, but there was someone selling buffing pads specifically for plastic. It worked great for me, just gotta be careful to keep moving around the tank so it doesn't get too hot and melt! Overall, I'm happy with the end result, it isn't show quality by any means, but this is a race bike, so I'm good with some character! Keep some cold beers handy and good luck!



















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Do It In The Dirt!

2/4/2020 7:03 AM

MaxPower wrote:

I got my a Kx tank back from the dead. I used an orbital sander.. Started with 150. Be careful you can remove slot on the corners. Keep stepping down . Finally wet sanding by hand. I cut circles from flat sheets of paper and spray glued each layer to the sander. It saved hours of hand sanding
The final shine came from a buffing disc in a cordless drill on slow
That tank can look new again

So you did a dry or wet sand with the orbital sander using the 150 grit sandpaper?

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2/4/2020 8:39 AM

Thanks for the inspiration!

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2/6/2020 12:17 AM

How do you get the final shine? Buff it with what?

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2/6/2020 5:01 AM

Robgvx wrote:

How do you get the final shine? Buff it with what?

keep wet sanding with finer grades like, 800 to 1000, to 1500, use dish soap in the water. Sand in 1 direction, not circular, occasionally using a sanding block. It almost starts to shine on its own. An small orbital buffer with a fine compound, it will shine easily. Buffing compounds are just like sand paper, so use a final polish type compound, not a heavy thick compound. Usually the fine compound is white in color. I spent about 2 hrs on this tank... the OP”s tank, I would start with a new razor blade in 1 direction to strip the worst of it, then start with 320 grit & work my way up to 1500 grit

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2/6/2020 11:24 AM

Robgvx wrote:

How do you get the final shine? Buff it with what?

sandman768 wrote:

keep wet sanding with finer grades like, 800 to 1000, to 1500, use dish soap in the water. Sand in 1 direction, not circular, occasionally using a sanding block. It almost starts to shine on its own. An small orbital buffer with a fine compound, it will shine easily. Buffing compounds are just like sand paper, so use a final polish type compound, not a heavy thick compound. Usually the fine compound is white in color. I spent about 2 hrs on this tank... the OP”s tank, I would start with a new razor blade in 1 direction to strip the worst of it, then start with 320 grit & work my way up to 1500 grit

When I did mine I sanded down to 2200 or something. It was really smooth but I just couldn’t ‘get that final shine. I tried all sorts of final compound: metal polish, plastic polish, cutting polish, even toothpaste. The finish was great but not shiny like yours.

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2/6/2020 12:41 PM

Robgvx wrote:

When I did mine I sanded down to 2200 or something. It was really smooth but I just couldn’t ‘get that final shine. I tried all sorts of final compound: metal polish, plastic polish, cutting polish, even toothpaste. The finish was great but not shiny like yours.

Here is what I used ... foam buffing pad, any fine cutting compound

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2/6/2020 1:21 PM

sandman768 wrote:

keep wet sanding with finer grades like, 800 to 1000, to 1500, use dish soap in the water. Sand in 1 direction, not circular, occasionally using a sanding block. It almost starts to shine on its own. An small orbital buffer with a fine compound, it will shine easily. Buffing compounds are just like sand paper, so use a final polish type compound, not a heavy thick compound. Usually the fine compound is white in color. I spent about 2 hrs on this tank... the OP”s tank, I would start with a new razor blade in 1 direction to strip the worst of it, then start with 320 grit & work my way up to 1500 grit

Robgvx wrote:

When I did mine I sanded down to 2200 or something. It was really smooth but I just couldn’t ‘get that final shine. I tried all sorts of final compound: metal polish, plastic polish, cutting polish, even toothpaste. The finish was great but not shiny like yours.

sandman768 wrote:

Here is what I used ... foam buffing pad, any fine cutting compound

Yes-- the Novus 1-2-3 method has always worked for me for the final finishing after doing all the scraping and sanding steps.

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2/6/2020 4:24 PM

You Can get something similar at most auto supply stores. I think I got this novus stuff from amazon on sale

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2/9/2020 12:06 PM

To those that have polished a kaw tank... how do you remove the brown discoloring spots that form in lower area?

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2/9/2020 1:38 PM

riv187 wrote:

To those that have polished a kaw tank... how do you remove the brown discoloring spots that form in lower area?

I have 3 older KX”s, have not see the brown you speak of....I would say if it doesn’t come off with razor blade or sanding it nots coming out...

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2/9/2020 7:02 PM
Edited Date/Time: 2/9/2020 7:04 PM

riv187 wrote:

To those that have polished a kaw tank... how do you remove the brown discoloring spots that form in lower area?

sandman768 wrote:

I have 3 older KX”s, have not see the brown you speak of....I would say if it doesn’t come off with razor blade or sanding it nots coming out...

Cu



Couple examples of the kx brown tank. I think it's deep in plastic,,,thought maybe someone will share the trick to getting in bright green again. I have thought of trying Gel40 hydrogen peorxide ,,then the scrape process???

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2/9/2020 7:41 PM

My guess would be it had fuel left in the tank for a very long time. Same happens on old Yamaha yellow tanks. Turns kind of a dark orange that is from the inside out. You can scrape it with a razor blade until you spring a leak then get another tank.

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2/9/2020 9:01 PM

Guys on Yamaha's way back in the day were turning their tanks brown from running straight race gas, God only knows what octane. Back then, YZ's with brown tanks were a common sight and they were not even a year old yet.....

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2/10/2020 6:19 AM

riv187 wrote:

Cu



Couple examples of the kx brown tank. I think it's deep in plastic,,,thought maybe someone will share the trick to getting in bright green again. I have thought of trying Gel40 hydrogen peorxide ,,then the scrape process???

awesome bike..... I don’t think that is coming out...Does evo-mx make perforated decals to cover the whole tank? Likely the best it would ever be...

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2/12/2020 12:47 PM

The final shine is easy. I used a regular buffing wheel. The kind that goes in a bench grinder. I got something from Lowes so I could fit in into my cordless drill. Use low speed. Fast will burn or melt the plastic. Couldn't hurt to use the final polish spray from the Novus 123.

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2/12/2020 12:50 PM

Ktm Kev, the first time I sanded at 150 was dry. I panicked thinking I trashed my tank
I stuck with it and kept stepping down . I impressed myself with the final results. In terms end, guys charging 200 to restore a tank aren't getting rich
Great job Zeke

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2/13/2020 6:51 AM

I am doing an 89 tank right now too and I have 2 questions. How do you know you are good to switch to the next grit?
I have been sanding with 320 and when it dries it looks worse like more white. Is that normal? I feel like it is.

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2/13/2020 6:58 AM

lcgordon711 wrote:

I am doing an 89 tank right now too and I have 2 questions. How do you know you are good to switch to the next grit?
I have been sanding with 320 and when it dries it looks worse like more white. Is that normal? I feel like it is.

When you go to the next lighter grit and you still see deeper scratches from the previous grit, you'll need to go back to the previous grit, or two. Each time you go to a lighter grit, you want to make sure you're not seeing any scratches left from the previous grit, because if not, you'll have some shiny scratches once after you've buffed and polished it out!

Some photos of your progress may help to guide you in the right direction.

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Do It In The Dirt!

2/13/2020 7:47 AM

Zeke27G wrote:

When you go to the next lighter grit and you still see deeper scratches from the previous grit, you'll need to go back to the previous grit, or two. Each time you go to a lighter grit, you want to make sure you're not seeing any scratches left from the previous grit, because if not, you'll have some shiny scratches once after you've buffed and polished it out!

Some photos of your progress may help to guide you in the right direction.

Thanks for that. I’ll get some pics as I go. Has some weird runs on the top of the tank that were maybe splashed fuel not sure. Super hard to get out. I’ve been using a razor blade. The rest of the tank is not bad.

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2/13/2020 8:29 AM

lcgordon711 wrote:

Thanks for that. I’ll get some pics as I go. Has some weird runs on the top of the tank that were maybe splashed fuel not sure. Super hard to get out. I’ve been using a razor blade. The rest of the tank is not bad.


Definitely more work with a razor blade before worrying about any sanding. You can also start with a more coarse grit before starting with 320. Some say 150, but I'd go with 220 as a start. If you do decide to call it a day, I'm first in line to buy that tank!
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Do It In The Dirt!

2/13/2020 9:18 AM

Zeke27G wrote:
Definitely more work with a razor blade before worrying about any sanding. You can also start with a more coarse grit before starting with 320. Some say 150, but I'd go with 220 as a start. If you do decide to call it a day, I'm first in line to buy that tank!

Thanks and it really does not look too bad. I will go pick up some 220 also. If I gave up I would just have our graphics buddy make some to cover the whole thing green. I wanna get it looking good tho. It’s not my tank either. Did get this for a good deal 100 bucks shipped. It does have a little insert issue.

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2/13/2020 9:26 AM

lcgordon711 wrote:

Thanks and it really does not look too bad. I will go pick up some 220 also. If I gave up I would just have our graphics buddy make some to cover the whole thing green. I wanna get it looking good tho. It’s not my tank either. Did get this for a good deal 100 bucks shipped. It does have a little insert issue.

I think I remember seeing that one up for sale awhile back. Yes, try some 220 and work back to the 320 and beyond. To me they look better all cleaned up, than covered in vented graphic material that never matches well. If you're looking for some retro graphics, check out Unbounded MX in the UK. They're the best are retro graphics, they have great customer service and even though they're in the UK, their turnaround time is quick!

https://www.instagram.com/unboundedmx/?hl=en

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Do It In The Dirt!

2/13/2020 9:44 AM

Zeke27G wrote:

I think I remember seeing that one up for sale awhile back. Yes, try some 220 and work back to the 320 and beyond. To me they look better all cleaned up, than covered in vented graphic material that never matches well. If you're looking for some retro graphics, check out Unbounded MX in the UK. They're the best are retro graphics, they have great customer service and even though they're in the UK, their turnaround time is quick!

https://www.instagram.com/unboundedmx/?hl=en

Thanks for the info. My buddy is good friends with defy graphics and we will get some stock ones made up. Going with a stock look. This one was bought from a junk yard so I don’t think it was ever up forsale. I’ll try the 220 and get this thing looking good. What’s the best order of grit? 220,320,400,600,800,1000,15,2000?

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2/13/2020 9:53 AM

Yes, you might even find that you can get 1200 grit as well. After 2000, you can continue on to 2500, but if it's not going to be a show bike, I would just hit it with a buffing wheel and some fine polish and call it a day. Also, once you get past 600 grit, you should only need 1 sheet of each. Keep us posted on your progress!

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Do It In The Dirt!

2/13/2020 9:57 AM

Just stick with it.instead of buying pads for my sander I cut circles from sheets and spray glue them to an old pad. Ditch that razor blade. This is 2020. We have machines to do work for us now. Get a cheapie orbital sander

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