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SPAD Diamond Dust

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Old 04-02-2012, 05:36 AM
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Default SPAD Diamond Dust

I have a SPAD Diamond dust I am setting up. It has a K&B 40 with a flow-through muffler that is strapped on.

The problem I am having are bubbles form in the tank and then it makes the running of the engine inconsistant.

How can I prevent the bubbles? Is it coming from too much pressure from the muffler? Vibration? (the tank has foam around it but is tie wrapped to the plane).

Help please.
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Old 04-02-2012, 06:17 AM
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Default RE: SPAD Diamond Dust

You either have an air leak in the suction line from the tank (it could be inside the tank), or vibration is foaming the fuel. Use a felt klunk from a gas engine installation to eliminate bubbles from vibration. Nothing except replumbing and/or using ties on the fuel lines will eliminate leaks. Good luck.
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Old 04-02-2012, 06:20 AM
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Default RE: SPAD Diamond Dust

What about an OS bubbleless clunk?
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Old 04-02-2012, 06:30 AM
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Default RE: SPAD Diamond Dust

I can see bubbles in the tank ... so I think the fuel lines are fine. I think it is vibration or too much pressure fromt he pressure tap of the flow-through muffler.
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Old 04-02-2012, 02:47 PM
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Default RE: SPAD Diamond Dust

You get less pressure, not more, from the flow thru muffler. Also much more noise. A felt klunk will take care of the bubbles in the tank. OS just charges more for the same thing you can get at the lawnmower shop.
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Old 04-02-2012, 09:19 PM
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Default RE: SPAD Diamond Dust

I use these and they work great:  http://www3.towerhobbies.com/cgi-bin...?&I=LXD741&P=7  The felt clunk also sounds like a good idea, I've just never seen one of those.


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Old 04-04-2012, 03:11 AM
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Default RE: SPAD Diamond Dust

For high vibration where you still have foaming, like racers, folks do use bubbleless tanks.  This is simply a tank, with a disposable baby formula bottle liner in it and your intake line inside the liner.  You put the pressure line to the outside of the liner and it all goes into an appropriate size tank.  You still want to use one of those brass or filtered pickups as it spreads out the fuel drawing area.  Now to fuel you need a syringe.  Get one or two big syringes and fill them with fuel.  Put the syringe on the fuel line, suck out ALL of the air from the liner, invert the syringe and put only fuel back in.  Put a hemostat clamp on the fuel line and swap syringes, suck out any air from the fuel line and fill your bladder, repeat as necessary. 

Tank runs and is adjusted just like normal but there is no air with the fuel hence no bubbling.  You can buy specialized tanks to do this, or you can just make your own like they used to before someone made specialized tanks.  You could also try running a bladder but usually the needle valves are too course for bladder type pressure fuel adjustment.  You might also try putting a squirt of Armor All into your full gallon jug of fuel.  Here you would shake a full gallon of fuel and see if it turns into a milkshake.  If it does add a squirt of Armor All, recap and shake again.  Usually just takes a squirt for the silicon agents to stop the fuel from foaming.  However your shaking of the jug is a dang site slower then a wide open motor and you could need more then the squirt.  Problem is sooner or later the silicon that calms your foaming problems also starts to build up on your glow plug and motor parts, so you don't want to just start pouring the stuff in.

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