The other day I went up flying and immediately noticed a strong gasoline odor, I've experienced this before when my floats needed replacing so I didn't get too excited, however I glanced at my fuel pressure which is usually just in the yellow band was now mid to upper green band. I decided to come back and land. When I shut down I found fuel running out of the lower cowl, I opened the oil door and saw the drain pan wet with fuel. I pulled the top cowl off and put the boost pump back on and saw fuel coming out of the bottom of the bowl under pressure. I took the carb bowl off and found the brass guide rod for the float laying in the bottom which exposed a hole completely through the bowl, this is not from wear it is made like this. The brass rods are slightly tapered and are pressed into the hole, however if the rod comes loose you have about a 3/32" open hole for the fuel to come out under pressure. Not a good design especially right over the exhaust pipe. The leak was large enough to drop my fuel pressure. BTW, I just had the carbs done at Lockwood about 90 hours ago...my carbs are perfectly synced and prop balanced to .04 IPS, she runs extremely smooth. I'm most likely going to buy two new bowls, at the very least those holes need to be sealed at the underside. I'm leary of pressing the guide back in and sealing the bottom holes...going to let Lockwood and Vans know about this.
Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Carb. Bowl massive leak experience
- Thread starter bobg56
- Start date
NinerBikes
Well Known Member
Strive to balance the prop to .01 IPS.
Piper J3
Well Known Member
What happens if a bug impales itself at the tip of one blade? Say 1 gram at 30" moment arm?
When you consider the number of 912ULS powered airplanes, gyros, drones, snowmobiles, and a number of other applications that use the 912ULS. Add to that there are others that use the same BING 64 carburetor, like BMW motorcycles.
This is the first I have heard of this issue. I don't think redesigning on a single incident is warranted.
What it looks like I'm going to do is re install the tapered pin by reseating and dabbing some fuel proof epoxy at the outside holes, this will hopefully accomplish two things, hold the pin in place and if it were to come out of place at least the hole won't be exposed to cause a serious leak. You may think that this is only one instance out of thousands of engines however if you saw the amount of fuel pouring out the bottom of the cowl, you would understand it should be addressed. Maybe all it will take is epoxy.
Talked with Lockwood today, they said the carb bowls have been re designed without the holes going all the way through, looks like I'll be ordering 2...they said the change was made a few years ago, should have been a SB for a heads up...plus he mentioned that the right carb seems to vibrate more than the left which is something I noticed myself doing running leak checks, something about engine harmonics.
Got the new bowls, they are a dark grey color instead of the original silver...there are no holes going through. According to Lockwood they have seen similar situations as what happened to me. I don't know why an Alert SB didn't come from Rotax. If you have the old silver bowls you may want to change them out or at least dab some epoxy over the holes.
