Possible fuel foaming in a Little Toni  
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Possible fuel foaming in a Little Toni - 4/21/2006 8:29:47 PM   
Andy_suncoast_sportplanes


 

Posts: 61
Joined: 2/18/2004
From: Naples, FL, USA
Status: offline 		I have test-run my new BSE90LX on a stand and am very pleased with the way it ran to the specs and advice provided. I was prepared for a 'tricky' break-in and carburetor setup for this 'peaky' engine, but very soon got it dialed in. It even starts every time by flipping the prop against compression and it throttles-up well.

So I put it in the Little Toni and first flight it quit after about 3 or four high speed runs, ie no more than about 3-4 minutes flying, albeit mostly at full throttle. The tank has 240cc molded on the side, so I guess about 8 oz (?). Anyway, I was suspecting VERY high fuel burn after two similar dead-stick landings. Taking the tank out, there's 1/3 fuel remailing. The clunk is in place and I had it plumbed correctly. I'm now thinking fuel foaming causing a lean-out and stoppage. The tank is not (as standard) foam mounted.

Anyone else with a fix for this apart from foam-isolating the tank? I did my best to balance the prop but at 15k rpm the prop/spinner combination is probably not perfect.

Finally, what should I expect in terms of run-time (high speed wide-open-throttle flight) should I expect from 8 oz?

Cheers, Andy
       Post #: 1

RE: Possible fuel foaming in a Little Toni - 4/21/2006 9:03:32 PM   
bob27s



Posts: 4590
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hi Andy,

Im glad the engine is performing to your expectations.

There really is nothing mysterious about the Jett engines. They simply run better than most. The carb is one of the best in the business.

As for your issue...

It is absolutely essential that you foam isolate the fuel tank... especially with that engine. If the tank is touching any part of the airframe, its going to foam the fuel. Make sure its wrapped in foam rubber, and does not touch anything directly..... its not worth risking a burnt up piston and sleeve set. There is no other way to fix that situation. And the armor-all in the fuel trick is just masking the problem... dont go that route if you can avoid it.

Many folks are now running either bubble-jett or tetra bubbless fuel tanks in the Minnow and Toni. Its a tight install in stock configuration, but with the bubble-jett type tank you can litterally cram the tank in place and have no worries about fuel foam. It just does not occure.

Typically we only suggest flying to about no less than 1/3 fuel remaining on a regular tank - particuarly for the issue you discovered. That last 3rd of a tank, the clunk is bouncing all over, often in and out of the fuel, and you are bound to pick up an air bubble.

The nice thing with a tetra or bubble-jett tank, is you can fly to the very last drop in the tank.... so often you can get away with a smaller than usual fuel tank (no worries of unusable fuel).

Fuel burn at full throttle on the 90LX is about 2 oz per minute. Lots of power comes from burning lots of fuel.

Something important. If you believe you have gotten the engine hot or it leaned out in flight, be sure to check the head bolts and ensure they are tight.

Let me know how you make out

Bob


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host
       Post #: 2

RE: Possible fuel foaming in a Little Toni - 4/22/2006 12:05:23 AM   
Andy_suncoast_sportplanes


 

Posts: 61
Joined: 2/18/2004
From: Naples, FL, USA
Status: offline 		Thanks, Bob, very useful feedback. I should first update that exising tank size - it was 420cc not 240cc as stated in the original post so it's a 14 oz tank. I want to fly this weekend, so I'll try a foam-isolated dubro 24 oz tank I just got from the LHS (yeah, too big I know) and see if I can at least get 2/3 of a tank out of it. I also invested in a new spinner so we'll see if the balance/vibration is better. Sounds from your comments though, that it isn't possible to eliminate foaming in standard tanks.

I think I'll get a bubbless tank ordered next week and put the problem down for good.

Thanks again - I will certainly check head bolts.

Andy

(in reply to bob27s)
       Post #: 3

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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> Possible fuel foaming in a Little Toni
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