Is it a California model?  They have a vent line up front on the bottom of the tank.  It's toward the right side.  If it's broken, you might get some gas through there on occasion.

You could empty it, pull it, shake it as empty a spossible, set it in the sun to let it evaporta out, a rag over the filler to keep syuff out, take a piece of innertube & seal off the neck, using a huse clamp, with a hole for a tire pump, sealed off with another clamp, air it up just a tad & feel for a split, talcum powde is good for showing air move. Or hang it up, set it up, whatever, & start filling it till it leaks. Lota of ways to track it down, just have to be creative. Maybe the first suggetsion wont work, may have to try different thiongs, but I cant imagine having a leaky bucket & not being able to find the leak, Its just a bucket, with a cap, now, you gotta find the leak,.

I just bought a used tank that has a leak in it at the bac by the mounting bracket (this leak was disclosed) and I have been doing some research.  There are the 'Kreem Coat' approaches -- basically etching and then coating the inside of the tank.  This is messy, expensive, and more trouble than I wanted to go through.  May be the way to deal with a tank from a classic car or other bike applications, but there is a technique used for aircraft that is promising.

BEFORE YOU START, MAKE SURE THE TANK IS TOTALLY DRY AND VAPOR FREE.  First, finding the leak:  I used a 12v air compressor (a shop vac with blower feature would be better).  Tape up or otherwise seal the petcock opening, then insert the compressor tube into the tank and seal up the rest of the fuel-fill opening with a rag, as snug as you can.  Apply a generous bead of Dawn liquid detergent to suspect area and start the compressor.  (This is how plumbers check for gas leaks.)  After a minute or two of goobering it up with Dawn I was able to detect the leak -- very small bubbles appeared.  Not much, but it doesn't take much for gas or gasoline to leak.

Fixing the leak:  I have not tried this yet, but there is a type of aircraft that is prone to corrosion/leaks in the fuel tank.  Some guy developed and got certification for a technique that involves both applying solvent to neutralize the oxidation (probably not a problem for most bike tanks) and a sealant to stop the leak.  This is done by reversing the process I outlined above for detecting the leak, i.e., seal up petcock, but insert the hose from a shop vac, seal with a rag/duct tape, turn on the vac, then apply the sealant to the hole area.  The partial vacuum created in the tank will draw the sealant into the hole.  When you are sure that the hole has been filled with sealant, turn off the vac and let it dry for a couple of days.

Here's tha catch: the kit for aircraft applications cost $560.  (Not a type - $560.00)  For that you get one ounce of solvent and one ounce of sealant and a couple of spray bottles for undertaking a certified procedure.  Here's the kicker:  analysis of this 'sealant' strongly suggests that it is, essentially, blue loctite.  Loctite, per se,  is not certified for this fix on aircraft, but we are free to experiment.  I intend to try the fix this weekend.  But if some daring soul cares to take the first step, be my guest and please report back.   Lotsa luck.

Thank you both for your replies....

I'm looking at new tanks now, (I wanted one for the build this winter anyways) and what the wife doesn't know....

Really, I think I might fix it as a back-up, and that Bill Hirsch product looks like just the ticket....

I knew you would all be able to help with an answer.

Shadowman, just so you know, that mounting bracket looks to be the scource of my leak also.....  

I will say this though, there was a dent across the top of the tank where I was told wood (a single 2x4, right....) in his shed fell on the bike and dented it... Looks like it did more than just dent the tank in my case.

Also POR15.  The Fuel tank stuff is suppose to be "impervious to all fuels, including the new Stage II fuels which have a high alcohol content."

http://www.por15.com/products.asp?dept=12

NOTE: You have to be careful with POR15. It sticks and sticks and sticks ...... If you get it on your skin it's there until you shed that layer of skin (trust me.....)

T Mack 1 - FSO wrote on 08/05/08 at 13:48:37:




Don't I know it.  When I first used it, it was 100 degrees outside so I only wore shorts and sneakers, and crawled under my car to paint all the rust areas with POR 15.  BIG mistake.  Nothing removes it and it took weeks for all the drips to wear off my body and face.  I have to say though, it is the BEST rust paint I ever used.  Once treated with POR-15, metal will not rust.  It rusts around the POR 15, but thats all.

Sluggo has a well bent tank, He might be happy to take your leaky one off your hands.