Endurance tank modification

So, we got a Clarke Splash Gas setup after being given some great advice from you guys last summer. Our pitstops/rider change went from 2+ minutes to 33 seconds. We won every race we entered after buying the quick fill.

Now our races are 3 hrs, and once last Sept, I was on the bike for 84 minutes straight, fuel light was on, when we crossed the checkers. I think it was on for 5 laps, but couldn't be sure as I wasn't watching the fuel light too close.

This year, we forsee being a rider short a few times, and instead of recruiting another rider, we would like to do a 2 rider race, each running 90 minutes straight.

Does anyone have any how-to or advice on how to strecth the fuel capacity on a CBR 929? We have a spare tank to chop up.

 

Check out the "Endurance Tank Porn" thread...several guys have posted "Ideas" on just that subject, just use those ideas to modify your Honda tanks...http://forums.13x.com/showthread.php?t=307862

 

A 929? Wow. Want to upgrade to an 03 GSXR1000? There are 2 quick fill tanks included(one stock size and one oversize).

 

To run in the GTU class, our bike has to be 12-20 yrs old.
Amusingly, we managed to do more laps than a couple of expert teams riding new litre bikes in the GTO class a few times, not only winning our class, but winning the whole event. Lucky for us, an almost stock CBR seems to be more reliable than a 200 hp built MV Agusta,LOL.


We only want 3-4 more litres, less than a gallon extra. I contacted a well respected motorcycle body man locally, and he said that to do a tank he would have to weld both inside and out to ensure it wouldn't leak, and that he couldn't do it. I was looking thru the other thread posted, and it makes me wish I knew how to weld.

 

Well I doubt that Britt welds his on the inside. I know I don't.

 

That's what I thought too. But this guy feels that to contain fuel it has to be. I don't imagine factory ones are welded in an out either....unless they have some fancy welder that can work thru the fuel filler,LOL.
I may try cutting up the tank, and just rasing the OEM fuel filler an inch or two, and make up the filler panels from sheet metal, and have a welding shop stitch it all back up.

 

Factory tanks are "Roll Seam Welded"...no I don't weld inside..except on the ones that cover the airbox (newer bikes with plastic covers)..then only the bottom part is welded inside.
I weld them outside, and pressure check them to about 10psi, spray the outside with soapy water...that is IF I have the block off plates to fit the tank, if not, then I just really pay attention when I weld them,.

 

I found some online photos of a high dollar ETI kevlar endurance tank for a 929 from back in the Erion domination days.
The extra fuel load was carried below the tank in a box formed shape molded to the bottom rear of the tank.
I got a hold of the machinist and fabricator I have enlisted before for other racebike mods, and he is quite excited to do the tank modification. So we are going to try to leave the top of the tank alone, and just modify the floor of it.

 

We did a 2002 GSX-R1000 tank like that, just dropped the bottom as far down as we could..it added about what you are looking for. Do yourself a favor don't use material any thicker than .045" or thinner than .035"...

 

Thanks...good tips from guys who've done it before.