Sport Pilot Talk

On another forum, a handful of owners have reported a recurring issue, which appears to be design-related and has serious safety implications.

When I first heard of a BING float pin coming adrift and causing a leak, I was skeptical, pretty sure the pins pressed into blind holes. I was wrong - such is not the case. The pins are a press fit into holes that pass right through the bottom of the float bowl, as seen here:



If a pin backs out of its hole, fuel will begin pouring out. This is an obvious safety concern - not all installations have properly plumbed drip trays, or drip trays at all. And there have been reports of the fuel flow out of the hole overflowing the drip tray. This fuel can end up in the vicinity of the exhaust, with possible dire consequences.

Anyway, I had my cowlings off today to troubleshoot a different problem (which I'll mention in another thread). I took the opportunity to check my float bowls. My pins all appeared secure, but I gave them a few light taps with a plastic-faced mallet to make sure they were seated. I think others have recommended removing the pins and reinstalling with a specific Loctite. I stopped short of that and just cleaned up the external surface and applied dabs of epoxy over each hole. I will make sure to check the pins at least at each annual.



Anyway, I think its a serious design flaw that needs to be corrected. I hope some of those who have had this problem have filed SDR's so that ROTAX and the FAA can propose a fix before someone gets seriously injured or even killed.

There have been a few of these lately. Usually caused by vibration which may be caused by out of sync carbs, old engine mounts or an out of pitch/out of balance prop. Make sure to keep these things in check.

The easy fix is to apply some Loctite 648 retainer to the post and press it back in place. With the retainer it should never come out again.

You can plug up the bottom hole if you want, but since the fuel can't come out there then it will overflow the carb and come back out the throat on the air cleaner side. Putting the JB Weld over the hole may just be a feel good type fix. Seating the post in properly with Loctite is a better long term fix.

roger lee wrote:There have been a few of these lately. Usually caused by vibration which may be caused by out of sync carbs, old engine mounts or an out of pitch/out of balance prop. Make sure to keep these things in check.

The easy fix is to apply some Loctite 648 retainer to the post and press it back in place. With the retainer it should never come out again.

You can plug up the bottom hole if you want, but since the fuel can't come out there then it will overflow the carb and come back out the throat on the air cleaner side. Putting the JB Weld over the hole may just be a feel good type fix. Seating the post in properly with Loctite is a better long term fix.

Thanks for repeating this advice here. You're my go-to ROTAX/BING guru.

I think we've heard of about 5 instances - you may know of more. But in what sized fleet? If our little community has had that many, is that in a background of 100 planes? A 5% rate for this kind of problem seems significant. Might you have a better idea of the sample size we're dealing with?

Excess vibration may very well exacerbate the problem with pins vibrating out. But I still hold its a design flaw - they should be designed to withstand any conceivable out-of-balance situation.

If the choice is having fuel pour out of the bottom of the carb or coming "back out the throat on the air cleaner side", I'd choose the latter. With the pin and float rattling around unsecured in the float bowl, I imagine all sorts of havoc would be raised with the mixture on that side, either way too rich or way too lean, in either case causing a power loss and a LOT of vibration. But I would still prefer that outcome to raw fuel in the engine compartment.

Anyway, I hope this gets addressed before someone gets hurt.

As I mentioned in the other forum this came up in, I don't even know if there is enough clearance for the pin to come out completely, since it's blocked at the top by the carb guts.

But this is a serious issue in my mind, because it did happen to me. I noticed it after shutting down the engine, the entire engine bay (including the exhaust pipes and the battery) were streaked with gasoline. I think there was at least a quart or two on the plane and puddled on the ground in the minute or so it took me look things over. When I was troubleshooting this, I turned on the fuel valve and a steady stream of fuel (looked about like the stream from a coffee maker) came pouring -- not dripping -- out. I'm sure I turned pale.

I think I was the first to suggest epoxy on the outer bowl holes, and I did that immediately on both carbs. I also used Loctite 648 as Roger described. The new float bowls are apparently going to be made with blind holes. I doubt Bing/Rotax would have made this change unless they considered this an issue. When they become available I will be upgrading.

Apparently the new

I think the title is a little misleading. Neither Rotax or Bing has issued an alert for float bowls.

3Dreaming wrote:I think the title is a little misleading. Neither Rotax or Bing has issued an alert for float bowls.

Consider it a "Fast Eddie Alert"!

That was really all I meant - that I was alerting other ROTAX owners about a potentially hazardous situation.

Sorry if it was misleading.

Maybe you could edit the title changing the word "alert" to "issues".

3Dreaming wrote:Maybe you could edit the title changing the word "alert" to "issues".

Done!

Sorry, did not mean to mislead - just alert!