tank craked near sub frame

[ZéPovinho]

I own a WR400'00 and all of a suddent a thin crack apeard near by the sub-frame under the bolt here goes the ruber bracket. I would like to know how many of you had the same problem, and in a few words, how did you fix it. I phoned the Yamaha and their answer was something like "were sorry, but, too bad..."

The point is, I can understand an engine failure, moving parts wearing out, electrical sistems burning out, but a plastic tank craking????!!!!!!!? on a bike that mainly rode Supermoto, so not too many crashes, hits, vibrations.

and the price here in Portugal is over 890 dollars:crazy:

thanks guys

ps.: a bigger tank is out of the question!

[Lennie]

Plastic weld it?

[changaz]

mine split near the side fairing bolt. basically the plastic had hardened, crazed and cracked.

got it plastic welded (professionally) its stronger than ever, doesnt leak, is not very noticable, and only cost $30aud.

[phynx]

JB weld works fine also. It happened to me last summer. I was using a zeta breather cap and it wasn't breathing!! Never again will I go for looks.

[matt4x4]

same year, same tank, same crack, same place.

Just plastic weld it one of two ways:

1 shave some plastic off the thicker inner corners of the tank to use as filler or

2 shave some plastic off a recycle bin to use as filler.

I like option 1 better since you are guaranteed the exact same platic composition instead of guessing at it.

Now start to melt the crack back together with a soldering iron (new flat tip no crap on it), working your filler material into the soldering iron while you are working your way down the length of the crack - go well beyond teh ends of the crack with your fix.

There's a great youtube video on how to do it.:

[phynx]

same year, same tank, same crack, same place.

Just plastic weld it one of two ways:

1 shave some plastic off the thicker inner corners of the tank to use as filler or

2 shave some plastic off a recycle bin to use as filler.

I like option 1 better since you are guaranteed the exact same platic composition instead of guessing at it.

Now start to melt the crack back together with a soldering iron (new flat tip no crap on it), working your filler material into the soldering iron while you are working your way down the length of the crack - go well beyond teh ends of the crack with your fix.

There's a great youtube video on how to do it.:

Man, that was great Vid! I tell you, we are always looking for a box of equipment that fixes are problems specifically or a professional, here in the US, but sometimes brainstorming and some common sense really work out better when you don't have access. IE Story: I was in MEX this last summer, and was clueless about fixing a rubber tire stop that goes in the wheel to hold the tire from spinning. We arrived riding in a small town 2000 miles away from the US border. We had tubes like crazy and other parts that sometimes break down, but rim locks!!... [ We here in the US just replace, right? We do this because it is more available for us, and at a fair price usually, or we can shop:moon:] Where would I order!!?? Well, in my group, I had my mexican buddy going into a little corner store in this dirt busted town & purchase two table spoons of baking soda and two 1oz super glue thingies and WALLA! He applied glue and as he was sealing it, he would add the BS. Man, I was amazed:p. It glued cast aluminum and rubber like nothing.. That bike has since done another 1000 miles through rivers, dirt and puddles. When you don't have, you learn to innovate. Thanks for sharing that Matt.

[davidl9999]

Yeah, but we're talking a gas tank here, not a bicycle wheel.

Gasoline vapor ignites at 495F, can flash (from a flame) at -45F and can spontaneously ignite at 536F. A soldering iron can get to over 800F. Do the math...

HDPE can be reformed around 140-160C (282 - 320F) and melts around 325F-550F (depending on the formulation). it needs to be at the fusion (melting) temperature - without scorching - throughout the depth of the crack in order for the weld to hold. The good news is that any weld can be built up to a full thickness as long as the thermoplastic is "fused" to the previous layer.

There are hot-air welders that you can get from Harbor Freight for this purpose starting around $30 and you can dial-in the air temperature so you never get near 495F. You can find colored HDPE rods online that match the tank color. They're about $10 for a pack (maybe a buck a rod).

An option is to purge the tank with co2, nitrogen, or argon before "welding" it; and it's also possible to fill it with water so that there's no gasoline vapor near your tool. Once a bit of plastic is formed over the leak, you can just build up the plastic weld in layers for a strong repair. That said, I don't recommend using heat on a gas tank once it has had fuel in it.

The downside is that whatever heating you do, it will burn off at least some of the UV protectants in the plastic, and damages the fuel vapor coating (to reduce evaporation through the tank walls) that's present in newer tanks.

Edited November 16, 2009 by davidl9999
can't spell...

[MaxPower]

I thought those tanks were huge. Buying and aftermarket tank to fit a YZ will make the bike much more comfortable to ride. Problems are easy to fix when you throw money at it

If you do get a YZ tank I may have a seat to fit

[matt4x4]

I successfully managed to fix several tanks this way without scorching or even changing the color of the plastic - mind you, it does require your brain to be turned on...if you're going to sit there and cook the same spot whilst inhaling the smoke, I can't stop you......

As for the gas fumes blowing you sky high...well....last time I checked....I was still alive and on this planet.

....UV protection - the crack is on the underside of the tank, unless he rides like crap and spends more time on the ground than in the seat, the likelyhood of that spot breaking down due to UV rays is also pretty slim

[davidl9999]

Funny thing...

Right now I'm "reforming" a 12 Gal topside HDPE boat fuel tank so that it will fit under the transom instead of having to carry around a pair of 6-gal portable tanks. Had to cut some windows out of the sides near one end of the tank and "heat and fold" the poly into a new shape with a propane torch. Would be easier in an oven, but I don't want the whole tank to get soft...

Anyway, I'll be welding the seams with a hot air welder as soon as I get the reformed part looking nicer than it is. (and yes, the tank never had gas in it...)

[ZéPovinho]

anyone ever had the sama tank problem as I did?