Fuel Tank leaks :-(

[Matt Crawley]

I used Mothers polish on my MZ 500 and that ruined the plastic, but not in the same way. It clouded the finish. The Mothers chemically reacted with the fender.

So maybe there was something that happened. This surely needs more investigation. Being a one off type problem, I would lean towards someone in the factory using a bad part, to finish the bike. All the other bad ones in the batch could have been scrapped and one slipped through. I think we would see more fuel tank issues if it were something else, unless you used some strange cleaning or polishing chemical, or some other form of additive.

I'm thinking "bad part" also. Maybe they had 500 bad tanks and 1 slipped thru. I did find a few mentions of leaking fuel pump gaskets (just like mine) but with no further problems.

The only thing that ever touched the outside of the tank was fuel and water with maybe a little windex here and there. And the other plastics are seeing the exact same conditions. Only the fuel tank is failing.

When I replace the tank I will find an uncracked section and do a test with fuel. I'm betting I can create cracks where I allow fuel to pool & evaporate.

The cracks look like stress cracks for the tank expanding and contracting.

Really? I'm not getting that feeling. The cracks don't seem to be in stressed areas. The cracks fall in exactly the way that fluid flows. In the photos of the side of the tank the front parts have more cracks because the leaking gas flows there under braking.

I think sending pictures off to KTM and Husky might be a good thing. We might see a fuel tank recall out of this.

I guess anything is possible but I'm not expecting they will have any interest at all.

You may be the first one of many due to age and chemical. Or not.

I hope it's an anomaly because it's a royal pain. Bike has only 4000 miles and has been indoors 90% of it's life so I doubt it is the "first one". Still... I would like to add some sort of exterior protection to my new tank. Problem will be trying to find something that sticks to the plastic... and doesn't damage it.

Matt

 

[Matt Crawley]

I think the expanding/contracting sounds like a plausible cause.
I could see with known issues of the vent ball thingy getting stuck the tank pressures might cause something like this.
I have not experienced this, but the "gas geyser" reports sounds like a lot of pressure.

Sounds plausible but I think there would be a lot more people suffering similar problems.

My tank actually holds a good bit of pressure since I patched it but held no pressure before that. The fuel doesn't leak all the time but it does when the weather gets hot. I get no leaks in the morning and evening but the other day was 90F and I was stuck in traffic for 20 min and fuel started bubbling out of the tank under pressure.

Oh and I already took the check ball out of the vent. That ball is to shut the vent if the bike tipped over. It's not supposed to control pressure but if it gets stuck it can stop all pressure from venting.


Matt

 

[Ogre_fl]

Sounds plausible but I think there would be a lot more people suffering similar problems.

My tank actually holds a good bit of pressure since I patched it but held no pressure before that. The fuel doesn't leak all the time but it does when the weather gets hot. I get no leaks in the morning and evening but the other day was 90F and I was stuck in traffic for 20 min and fuel started bubbling out of the tank under pressure.

Oh and I already took the check ball out of the vent. That ball is to shut the vent if the bike tipped over. It's not supposed to control pressure but if it gets stuck it can stop all pressure from venting.


Matt

What you describe sure sounds like a vent issue and that you still have one.
I don't have any vent issues, I have no idea if my tank can take any pressure.....because it never sees any.

 

[Matt Crawley]

What you describe sure sounds like a vent issue and that you still have one.

I know I took the ball out. I'll double check tonight to be sure that it is venting.

Matt

 

[Matt Crawley]

What you describe sure sounds like a vent issue and that you still have one.
I don't have any vent issues, I have no idea if my tank can take any pressure.....because it never sees any.

My tank is venting pressure correctly.

Technically ALL fuel tanks see pressure in that the weight of the fuel is trying to push out of the bottom and sides of the tank all of the time. That is what happened in my tank. I filled the tank to below the level of the fuel pump gasket the night before but in the heat of the day the fuel expanded above the fuel pump gasket and pushed out.

Good news is that the replacement tank showed up today from Ebay. It looks really nice with almost no wear and ZERO cracking. Now I need to figure out time to do the work.








Matt

 

[Matt Crawley]

I finally pulled the old tank out last night.

The Workshop Manual says you can do it without removing the rear subframe. You can't.

Wondering what else I should do while I have it all apart.



Matt

 

[Mark_H]

I finally pulled the old tank out last night.

The Workshop Manual says you can do it without removing the rear subframe. You can't.

Wondering what else I should do while I have it all apart.

Matt

You can sort out that crappy Mudflap arrangement to put a stop to the water entering the swingarm.
Obviously it can be done without the bike in pieces, but now is easier to do.

 

[turtlemoye]

Replace the upper shock bolt with the strongest possible one you can find or you might be replacing that tank again soon.

http://www.cafehusky.com/threads/gas-tank-replacement-and-shock-warning.80863/#post-554654

Probably should replace the lower one to just to be on the safe side.

 

[Bluff Boitjie]

Remove the steel ball bearing in the tank lid breather valve