Are they called matches?:D

Jim,
Simultaneous failures (tank and floats) are unlikely. The last thing you worked on prior to the fuel smell was the tank. I would close that issue before galloping off in other directions. Ben Barron had a tank leak that was hard to find and he did find it with dye.
Check out this this thread for the dye he used: http://www.vansairforce.com/communit...ght=dye&page=3

After rebuilding my tank and applying SBs, I had one slowly weeping rivet down in a corner. Fortunately I was able to get to it and seal it up. However, it was a very slow seep -- maybe a drop every few minutes. You could smell it in the cockpit after closing the canopy for a while. I think that would be true of any tank leak, except maybe the collar where the filler neck attaches to the tank. The return line pumps fuel into that area, so I suppose it's possible it could be the source -- although you'd almost certainly smell it while fueling. If you fill yours halfway up the filler neck like I do, it would be obvious after sitting for a while.

So if you're smelling it only during flight, especially on climbout, I'd be more suspicious of a firewall forward source. The carb floats do sound like a likely source. I would maybe try some slow flight at high angles of attack at idle and part throttle to see if it happens with certain engine speeds, certain loads, or just certain attitudes. That might help nail it down. If the float bowls are overflowing during flight I wouldn't be surprised to not see anything in the drip trays -- there's probably a good bit of turbulent air in that area to blow stuff around.

If my floats have become "heavy" and need replacement, has Rotax come up with their new float design yet? I can't believe how expensive these little buggers are. If current PN is 861-184 then it looks like $93.50 will buy a single pair of floats. Of course there's two carbs so twice that amount to make things right.

I'm going to buy AC Delco 10-5045 Multi-Purpose Fluorescent Leak Detection Dye and a 100 LED UV Blacklight Scorpion Flashlight to survey the tank for leaks. This will be the starting point for troubleshooting the fuel smell.

Thanks guys...

Check the pans under the the carbs for any fuel puddling. It looks like oil if you run car gas.

Also make sure that the fuel vent mod line is still attached behind the baggage bulkhead. I'm not a fan of that design.

I have also been trouble shooting a gasoline smell in the cockpit of my RV-12. After failing to find any leaks, I finally looked behind the bulkhead behind the tank and found the problem. There is a "T" in the overflow tube where the 1/8 " clear tube is connected to kill any tendency to siphon. This 1/8" tube had pulled out of the "T". Furthermore, this part of the "T" was angled downward, so that when I filled the tank to overflow, fuel was dumped into the fuselage via the open part of the "T". Also, it looks like I'll have to fabricate a new 3/8 aluminum overflow tube because the old one is too short and terminates inside the belly grommet. This could also possibly dump some fuel inside the fuselage. This tube is suppose to extend through the grommet to the outside by 1/2 " with a 45 deg bevel facing forward. I may can just do a small amount of bending and get it to protrude through the belly. It's awfully hard to access that area though

Fuel Valve Assembly Leakage
 

We had a similar problem on my -12 where a raw fuel odor seemed to occur on initial climb out and dissipated soon thereafter. Like others, we originally suspected that filling the tank into the neck may have been the cause, but avoiding that condition changed nothing. The odor was soon present throughout much of our subsequent flights and we grounded the plane until we could find the source.

When I finally looked at the bottom of the fuselage (duh...), I found fuel stain streaks that began aft of the firewall, suggesting the problem was not coming from the engine. So we openned fuel valve floor panel and discovered no standing fuel but residue was clearly present. Although the fuel valve line connectors seemed sufficiently tight, we disconnected them and added fuel-appropriate thread sealer to the lines and reassembled.

That solved the problem for us.

Good job!!

Question... Does anyone know the weight of a set of new floats fresh out of the box?