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Gas Tank Leaks from Mounting Bolt Spot Weld

Use this area to post problems that may arise, if you could use some help in figuring out what is wrong with your bicycle motor and what needs to be done to achieve top performance.


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  #1  
Old 08-15-2010, 11:34 PM
heathbar11 heathbar11 is offline
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Default Gas Tank Leaks from Mounting Bolt Spot Weld

I am hoping somebody has a solution. I am on my 3rd stock metal gas tank. Every one I install I tighten just enough for the tank not to move from the engine vibration. The weld that always fractures first, is for the bolt closest to my left leg (front tank mount) I have searched for plastic tanks and there does not not seem to be any. I was also thinking of tank sealer? I need a solution that works. Anyone have any success stories to share? Heath
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Old 08-16-2010, 01:29 AM
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Smile Re: Gas Tank Leaks from Mounting Bolt Spot Weld

Welcome to the forum Heath! Yes, I've had this happen to one of my tanks, the right rear mounting bolt eventually devloped a crack in the welded area. I was able to repair it using a 2-part epoxy, it might have been JB weld in fact after I drained the tank thoroughly and wire brushed the crack and surrounds with a wire wheel. Before the epoxy set up I slipped a self-adhesive, fairly dense foam rubber disk that I had punched a hole in, over the bolt and covering the patch. I put these disks (about an 1/8" thick and an inch in diameter) over the remaining 3 mounting bolts to help cushion the vibration. It never leaked again and it's still in service.

If that didn't work, I would have just brazed or welded the crack. Cheers and good luck!



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Last edited by scotto-; 08-21-2010 at 10:48 PM. Reason: pics
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Old 08-20-2010, 09:20 PM
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Default Re: Gas Tank Leaks from Mounting Bolt Spot Weld

Welcome to the forum. I was going to suggest using an old fire extinguisher for a tank but try scotto's method first.
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Old 08-20-2010, 09:25 PM
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Default Re: Gas Tank Leaks from Mounting Bolt Spot Weld

A little trick for sealing tanks from the outside. Make sure your petcock is closed, duct tape the hose from a shop vac to the fill, turn on the chop vac and apply the epoxy. The vac will create negative pressure in the tank and draw the epoxy into the hole/crack.

A vacuum pump works best but not everyone has one of those.
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Old 08-20-2010, 09:50 PM
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Wink Re: Gas Tank Leaks from Mounting Bolt Spot Weld

Quote:
Originally Posted by Kevlarr View Post
A little trick for sealing tanks from the outside. Make sure your petcock is closed, duct tape the hose from a shop vac to the fill, turn on the chop vac and apply the epoxy. The vac will create negative pressure in the tank and draw the epoxy into the hole/crack.

A vacuum pump works best but not everyone has one of those.
That's a great tip Kevlarr, every bit helps. And another little tip is wipe the area and surroundings with acetone or MEK just prior to patching the crack.
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Old 08-21-2010, 09:47 AM
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Default Re: Gas Tank Leaks from Mounting Bolt Spot Weld

I use silver solder to seal those cracks.

A trick that I learned for mounting the tanks, is to put some good 'double sided' tape on the top tube of the frame (to keep the tank from moving) so that you don't have to tighten the tank studs too tight (& possibly crack those welds.)
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Old 08-21-2010, 10:09 AM
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Default Re: Gas Tank Leaks from Mounting Bolt Spot Weld

I bought some tank sealer for marine fuel tanks from a NAPA auto store. I lived on the California north coast and was also worried about the fuel tank rusting on the inside and screwing up the carb. I applied 3 coats of the sealer to the tank. The last coat I bolted the tank onto the bike and just poured enough sealer to cover the stud welds then drained the excess out of the petcock. Never had any issues with leaking after that.
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Old 08-21-2010, 02:21 PM
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Default Re: Gas Tank Leaks from Mounting Bolt Spot Weld

Quote:
Originally Posted by Venice Motor Bikes View Post

A trick that I learned for mounting the tanks, is to put some good 'double sided' tape on the top tube of the frame (to keep the tank from moving) so that you don't have to tighten the tank studs too tight (& possibly crack those welds.)
Very good point. I use this Scotch Exterior Mounting Tape



With this tape you almost don't even need to bolt the tank down. You may find when you remove it it'll take the paint off your frame and tank before it lets go.
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Old 09-13-2010, 04:53 PM
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Default Re: Gas Tank Leaks from Mounting Bolt Spot Weld

I tired to fix my tank 3 times with JB weld...it pop at the mounting bolt also...its about a 1/2 inch crack...I guess i just need a new tank! or take it to a weld shop...any other ideas
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