spontanous cracking and leaking fuel tank...what the???

[motometal]

smelled fuel in the garage, at first assumed it was one of my old "project" bikes as they have a reputation for this...all dry there. Checked the gas cans, one was missing a vent plug, no big deal but couldn't figure anything else out. Later on, I walked by my KX100 and was amzed to see a huge puddle of gas under it. I haven't even touched this bike for weeks.

Upon closer inspection, there is a crack about 1" long going from the petcock hole outwards. It's not a "hairline" crack, it's actually pretty wide! Then later I noticed the filler neck is cracked about half way around, where the neck meets the main body of the tank.

Anybody else have this problem? I am using Sunoco race fuel, but have been using this in a variety of bikes for years. It's a race bike, should be able to handle race fuel but you never know.

and replacements are expensive, $170 for a "cheapie" aftermarket on up to $200-$300 for a stocker or an IMS.

This comes at a time when I was considering trading up for a newer KX. Now I get to take a step backwards. :|

 

[Camstyn]

That sucks.. I wouldn't recommend an IMS, the fit/finish sucks. I've heard good things about Clarke tanks.

 

[nephron]

I can see a family member or friend dropping it, picking it back up, whistling and walking off. ;) Do the cracks look like a chemical issue...ie, is the plastic weakened/soft around the crack? If the cracks were erosive, you wouldn't expect to suddenly see a puddle of fuel, but a chronic leak with complete evaporization and no puddle??? Consider that the petcock is a major point of stress in a fall, and that the filler neck would be in less contact with fuel than other parts of the tank. :think: I think the culprit is a mammal, and not a fuel. :coocoo:

If you want to go the real cheap route, fix it with epoxy, sand and paint....? Course, that would be half-arse.

 

[bikepilot]

It would be hard to hit a KX100 petcock in a fall, its tucked underneth the tank so far. Both the 1991 and 2003 KX100's (well 107 and 105 respectively) at my place have the oem tanks with no problems.

Egay often has oem tanks for these bikes for cheep. Is the 00 the old single shroud style or the newer symetrical style? If its the older style why not use this as an excuse to upgrade?:)

good luck

 

[motometal]

nephron, the cracks actually look different from each other. The filler neck one is jagged, not a straight line, and the plastic is porous in that area. The petcock one is a very straight line, and it's opened up a fair amount near the petcock. Neither one is soft near the crack. If it's from mechanical forces, then it's from a long time ago because the tank has been mounted on the bike undisturbed for a long time, don't have kids, and the wife doesn't mess with the bikes.

Bikepilot-mine is the older style with single shrowd, they switched in 2001 I believe. Can you say for sure that the newer style tank and shrowds will bolt right on (that is, you're sure they didn't change the frame)?

Will a stock KX tank run a 2 hr scrables without refilling? I wouldn't mind upgrading to a larger capacity tank, but the $$$...

thanks guys!

 

[nephron]

Hey motometal--just out of curiosity..why a KX100? Do you get into a more 'desirable' scrambles class with it, and if so, why? I've got a KLX110 just to fart around with, but haven't thought about a 100cc 2 stroke? The other reason is that I made the mistake of taking a powervalveless KX60 out on a grass field a couple years ago and damn near died. ;)

 

[Kav]

my YZ did the same thing when it was newer. I figured it was due to the extream desert diffrence in day and night time temps where I was at, and the valve in the tank vent line getting stuck closed. was your tank mostly full, and do you have a big temp diffrence where you store you bike. mainly does it get really hot where it's stored at?

 

[DWreck]

Nephron, I heard a story at Dirt Week the year before last about a certain someone riding in the woods on his KX250 (rider to remain nameless) first smelling race gas and coming around a corner and seeing a KX100 and thinking it was a kid. The rider looks back and sees him, grabs a handful and disappears into the woods like a lightning bolt. Poor guy was devastated. Turns out it was Motometal. So to answer your question he hauls butt on it in the woods.

 

[Rooster]

Moto - my best guess is those crazy stickers you put on your bike caused the tank to crack :laugh: or perhaps you had your bar adjustments set on the wrong dinosaur?

 

[JPIVEY]

That pretty weird, I've had 4 IMS tanks on 4 different bikes and never had a problem

But, I have repaired some stock tanks with this stuff and it works pretty good

http://www.urethanesupply.com/5500ht.html

Look around and make sure you get the right rods and they have them in colore to match most any tank

I repair a 4" crack in a old IT 465 tank, so far so good

 

[motometal]

wow...I got behind on this one

Nephron, I have never run the KX100 in a hare scrambles. Two weeks ago, I did my first scrambles in about five years, ended up on the CR250R instead. Anyway, why would I want to run the KX100? It's a complete hoot! Sometimes I get more grins from the first 10 minutes on that little bike than I do all day on the CR. Plus, I am really out of shape, and trying to ride the 250 for two hours (which actually ended up more like three hours) made me so tired I almost fell of the bike. Little bikes are less tiring to ride, other than your clutch ringer and shifter toe. As far as racing class, i'm not really worried abou that, to me just finishing is an accomplishment. We have guys that can ride just as fast after two hours (with no pit stop) as they did on the first lap, and i'll never hang with that anyway, so it's just for fun.

Do not try big triples on the KX100. Bad idea.

Kav- to answer your question, the bike is kept in an attached garage with a concrete floor, temp doesn't swing all that much although we are coming into the hot season.

Rooster, regretably the combination Ding Ding Bell and Dinosaur Performance Adjuster has been retired due to damage from a low hanging tree branch. Maybe the bike is going through withdrawl.

JPIVEY, that welder looks great. I wish I knew someone that had one. I'd be more tempted to go that route if the crack wasn't intersecting the sealing surface for the petcock. With an attached garage, it's no fun to have spontaneous fuel leaks, and i'm not sure if I want to risk a repeat problem. With multiple bikes (some of which are older than me), I get enough of that already (dried up petcock seals, sticking carb floats, etc.)