Carb floats

Pat Stewart · #1 01-10-2016, 02:57 PM

I have been experiencing a fuel smell on climb out and a lingering smell once back in the hangar. Checked all the fuel tank and fuel line connections and all is dry. When I put my hand under the carb filters I get wet gas. My filters elements are starting to turn white from red.

I went back and looked at the Carb float SB and if reading correctly my engine and carbs are outside of the range. My engine serial no. Is 6779981, my l/h carb ser no is 116358 and the r/h is 120372.

When I start the engine cold with choke on the engine runs just a little rough so I immediately push the choke back in which drops the rpm and forces me to add a little throttle to keep rpm in the green. Other than that this thing runs great. Just don't like the possiblefuel issue.

For those that may have experienced this in the past I would appreciate your feedback.

jabarr · #2 01-10-2016, 03:03 PM

Recently found the old floats (all of which were overweight) in an Aircam in which both engines/carbs were outside of the range of the SB. Obviously the SB doesn't cover all of the bad floats.

Sink · #3 01-10-2016, 07:50 PM

The old floats and the new floats are exactly the same composition. The difference is that the new floats have 3 acceptance test performed where the older floats only had two. The new additional test is a liquid pressure test. The new floats have two dimples on them to make them easier to identify. The old floats or floats not within the SB can still sink. Some floats last to TBO and sometimes one can get heavy. It has always been that way.-

If you have a sinking float the carb will flood and the engine runs rough at idle, you have fuel smell and can see fuel in the carb vent tubes or dripping into the drip tray. If you go up into the higher rpms like 5200+ then the engine smooths out as the throttle advances because you are now using that fuel and it isn't flooding the carb.

rv9builder · #4 01-10-2016, 09:38 PM

Rotax has had float problems, Lycoming has had float problems...of all the things to go wrong in an engine, you would think that making floats would be relatively simple. Why has this been such a problem over the years for aircraft engines?

f1rocket · #5 01-11-2016, 05:30 AM

Also as an FYI, I use the choke on my airplane the same way as you. It's not really a traditional choke as I understand it. As soon as it runs for about 15 seconds, I close the choke cable and open up the throttle to bring it to idle RPM to let it warm up. With the carbs balanced, it runs very smoothly there, not so with the choke out.

WingedFrog · #6 01-11-2016, 08:19 AM

You can confirm the float issue by weighting your floats. The acceptable range was provided in a recent post. I have in my RV-12 one carb outside the range of "bad" floats and one within. Interestingly the one outside weights more than the one within although both are within acceptable weight range. This just confirms what Sink is saying as well as the need to monitor by weighting your floats during annual inspection. It is easy and fast to do.

Pat Stewart · #7 01-11-2016, 06:53 PM

I will be weighing them this weekend. Talked with Lockwood and they have them in stock.

rv3flier · #8 01-12-2016, 04:35 PM

This is a heads up for those who intend to order new floats from California Power Systems. I just received 4 floats I'd ordered that were shipped in a mylar pack!!!! There were 16 perforations in the outer package caused by the pins on the floats. Two of the floats were damaged by the pin(s) of other floats in the package. Incredible. If you place an order, make sure you make a note to have them shipped in a small cardboard box.

The capper is that CPS is filing a claim against UPS to have the floats replaced -- when it's their screw up. While I'll get new floats shipped directly from CPS it's really unfair to UPS.

jrich · #9 01-14-2016, 10:03 AM

After installing the new (2 dot) floats, we found fuel pouring out the right carb. air filter on one occassion. Upon carb. inspection, we noted significant wear on the bottom end of the needle valve. There was so much wear that the retaining clip was going to be lost. Also, the mating face of the float arm bracket tab had a .006? wear depression. The arms of the float arm bracket were obviously not parallel with the carb base as required by the Rotax manual. We put a new needle valve and float arm in the right carb. and got the float arms very nearly exactly parallel to the carb. base. Re-assembled the carb., remounted it, turned on the electric fuel pump to check for leaks and there was no leak from the right carb. But, there was fuel dripping out of the overflow tube on the left carb. We were going to clean and inspect the parts on the left carb. anyway, so we did the same for the left carb. and found exactly the same conditions for it as for the right carb. This engine had between 325 and 350 hrs. at the time. Even after this, we've noted some evidence of minor residue on the drip trays which tells me that fuel comes out of the overflow tubes on occassion.

PilotBrent · #10 01-14-2016, 10:13 AM

Quote:

Originally Posted by jrich

After installing the new (2 dot) floats, we found fuel pouring out the right carb. air filter on one occassion. Upon carb. inspection, we noted significant wear on the bottom end of the needle valve. There was so much wear that the retaining clip was going to be lost. Also, the mating face of the float arm bracket tab had a .006? wear depression. The arms of the float arm bracket were obviously not parallel with the carb base as required by the Rotax manual. We put a new needle valve and float arm in the right carb. and got the float arms very nearly exactly parallel to the carb. base. Re-assembled the carb., remounted it, turned on the electric fuel pump to check for leaks and there was no leak from the right carb. But, there was fuel dripping out of the overflow tube on the left carb. We were going to clean and inspect the parts on the left carb. anyway, so we did the same for the left carb. and found exactly the same conditions for it as for the right carb. This engine had between 325 and 350 hrs. at the time. Even after this, we've noted some evidence of minor residue on the drip trays which tells me that fuel comes out of the overflow tubes on occassion.

Curious if these carbs were disassembled and inspected at 200 h per the Rotax maintenance recommendation, or was that skipped?