Hello, I need info on repairing a plastic gas tank. On my KDX the top at the filler is cracked, I’ve tried a few different things, no luck. I’ve tried Seal-all and the putty sealer.

Plastic welding "might" work.

Best option is replace tank.... I've never had much luck repairing.

I’ve repaired plastic, but to hold up exposure to gas is another problem. I’ve repaired plastic with a soldering gun.

old fasioned jb weld does a great job, you could sand it and paint it over too. Id say weld the plastic, then add a coat of jb weld for strength just to make sure that it doesnt leak any more.

We had a plastic hot air welding gun at work. I never used it but one of the guys was an expert at using it. Not tanks though just everything else.

I've plastic welded 2 tanks with the same results....They both lasted about a day with fuel in the tank, then they cracked again near the weld. You would be better off getting a new tank in my opinion.

Harbor Freight has a cheap plastic welder, I’m going to give it one last shot. Used ones are about $200. I see new ones $250+, but they are oversized, I prefer stock size tank.

I've done some plastic welding thanks to whitewater kayaking. Done well, it can hold up incredibly well. Just like regular welding, it takes skill and most importantly, lots of practice. Someone good at it can lay down a bead which looks almost identical to a metal weld, which can then be sanded down.

Look for a similar HDPE plastic to practice on, ideally a junk tank of same year/mfg, so you can get your temperature dialed on it. In the ideal world you want to cut a V down the length of the crack, then use a "rod" of same plastic material to weld into this v and get bonding all the way through the thickness of the tank, and surface weld wont hold. In the kayak world the best welding plastic comes from the same boat, there is enough excess on the inside of the cockpit rim to cut a welding rod thickness off. Another reason a junk tank would be handy (as a plastic source).

Too hot and the plastic will melt and loose integrity, heat too large of an area and the tank will warp making the crack worse. Too low and it won't bond. It's all about finding that ideal temperature and then learning how to apply heat back and forth (small waving motion at the correct distance) between the rod and crack as you go to heat both just enough.

I tried JB Weld on a plastic dingy (small boat) that I use in my pond. The wind flipped it over and cracked the hull along the center keel. JB Weld would not adhere to this plastic. Several other glues and sealants failed as well. Low and behold, Shoe Goo ended up adhering to the plastic as if it was welded together. This was many years ago and it is still holding strong. I just can't say how it would hold up to the fuel exposure. But it's worth a shot.

Edit:
Never mind..... Shoe Goo dissolves in gas.
thumpertalk.com/forums/topic/36249-any-s...goo-users-out-there/

i bought this stuff.

im one of those that spends bucks and tries a bunch of ideas but realizes in the end ill probably have to buy what im trying to fix.

www.harborfreight.com/80-watt-iron-plast...lding-kit-60662.html
JB Plastic Weld
Seal-All