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Old 07-20-2008, 12:55 PM   #1
mscuddy
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Default Plastic Gas Tank Repair

A buddy of mine's old CR480 gas tank is spider webbed and looking bad.

Was wondering if any MOron out there has used tank sealers on plastic tanks with favorable results? I've used a sealer on fiberglass with good results, but never plastic. Looked for plastic gas tank sealers on the internet, nada. Only this one, which says maybe, yes and no.

Gas Tank Sealer - Large Motorcycle Tank Sealer Kit - Better then Kreem - KBS Coatings
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Old 07-20-2008, 01:02 PM   #2
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I thought that you just replaced plastic tanks. Once they start to go the plastic rot will just expand. I guess he could patch the exterior with fiberglass. but the plastic is drying out. Better to just replace it.

He's not supposed to keep a bike that long remember? Honda wants him to buy a NEW IMPROVED 4-stroker. Sure, the new ones are slower and break more often. But that's the price we pay to ride works type machines.
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Old 07-20-2008, 01:38 PM   #3
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Yeah, believe it or not, his 480 is still competitive. It got four out of five stars in a recent dirt bike rating report (off-road.com).

Except for horrible headshake, the 480 still hauls ass. All 480 plastic parts are un-obtainium btw.

*uck four strokes and the designers who rode in on 'em. It's killing the sport. No too many 20 year old kids have the $$$$ to keep one up, so they usually save up for a year, buy one, and when it wears out, they sell it and take up tennis, or show boarding.

I see it all the time. Or they eat it big and ruin something bad enough on their body to quit altogether. My dirt riding buddy has 4 daughters, and all thier boyfriends ride, but when they eat it, that's the end. By by crf450. One even went the Scientology route.

I'm just gonna suggest to use the regular tank sealer stuff (for steel tanks). If it ruins the tank, wtf? It's gone anyway. Nothing to loose.
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Old 07-20-2008, 01:39 PM   #4
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Use the plastic tank as a mold to make a new fiberglass tank. I did this with terrific results for an ultralight airplane. You'll need to get some mold release wax, gelcoat, polyester resin, and some woven and mat fiberglass. Take the old tank and slice it in half. Coat the halves with release wax. Spray in the gelcoat (you can brush it, but spray is better) You can mix in a color with the gelcoat, or make it white for painting. Then you lay up the woven fiberglass, follow with the mat soaking them with the resin. Once the halves are done, you can join them with fiberglass tape and epoxy.

If there is ethanol in your area fuel, you may want to use epoxy instead; there's been problems with the alcohol eating up the glass. Another choice is to just lay the glass over the old tank and encapsulate it, but it will not come out as good looking as the reverse mold method.

Here's an article on the process; it's written for building a kayak, but the steps are the same. SWEET COMPOSITES - Fiberglass Mold Construction & Maintenance
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Old 07-20-2008, 01:44 PM   #5
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jeezus Ken, this guy can barely un-screw a bottle cap. That's a great idea, but ranks right up there with the lost wax casting process, or alchemy for "Dave".

I'll foreward the link, but it'll probably glaze over his eyes, and he'll want to take a nap or something.

Thanks.
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Old 07-20-2008, 02:15 PM   #6
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Quote:
Originally Posted by mscuddy View Post
jeezus Ken, this guy can barely un-screw a bottle cap. That's a great idea, but ranks right up there with the lost wax casting process, or alchemy for "Dave".

I'll foreward the link, but it'll probably glaze over his eyes, and he'll want to take a nap or something.

Thanks.
I thought YOU'D be doing it for your pal! After all, you've already got the thinner and clean up solvents brewing... Hell, if those plastic parts are that hard to get, there'a probably a small fortune awaiting someone who re-produces them. Someone who starts with a large fortune, that is.
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Old 07-21-2008, 07:32 AM   #7
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Matt,

+1 on the rotten plastic. Once the 'plasticizer' is gone, the stuff that's left is brittle. Best example is your favorite old Frisbee. Works great for a year or two, then it hits a curb and explodes!

He's gonna have to either fab a new one out of FRP or aluminum, or he'll have to park it.

I suppose he could bungee a 2-1/2 gallon gas can to the bike, but that'd look goofy.
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Old 07-21-2008, 08:22 AM   #8
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PR, we were thinking the same thing, two 1 gallon aluminum hydraulic fluid accumulators from this aircraft salvage place in Sun Valley. Also seeing if a tank from a later model CR fits...ahh the old bike blues, that's why I like restoring bikes from the early to late 70's, all steel with very little plastic.
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Old 07-21-2008, 08:44 AM   #9
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You can buy off road fuel tanks all over the internet. So what if it ain't an exact match? You got a drill, right?
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Old 07-21-2008, 09:41 AM   #10
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Quote:
Originally Posted by seruzawa View Post
You can buy off road fuel tanks all over the internet. So what if it ain't an exact match? You got a drill, right?
Universal desert tank, duct tape hose clamps and a drill will make anything fit.
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