Medallion .15 NVA nipple size

944_Jim Wed Jul 31, 2019 9:16 pm

I have this untested Medallion .15 that failed to run tonight. I suspect the NVA may be from a smaller engine because the only line I could get to stay on it was my smallest silicone line. The fuel nipples on my Norvel Big Migs are significantly bigger.

Anyone here have a known, good running Medallion .15 and a digital caliper? I'd love to know what diameter your engine's nipple is.

One thing for sure, this engine is going to see bench time before I try it on the speed plane. I want to know IF it will run solid just sitting in my test stand after washing several ounces of fuel priming the SOB!

Thanks in advance,

The flamed-out Jim

dckrsn Thu Aug 01, 2019 4:02 pm

Hi Jim,
I measure .125" at the widest point of the nipple on the Medallion .15.
The .049 and the .09 spray bars have the same size nipples, in fact the spray bars are interchangeable and use the same needles.
The .15 has the same size nipple, but the needle is different. I don't think the .049/.09 spray bars will fit into the .15 body, but
I guess that doesn't matter.
Hope this helps.
Bob

944_Jim Thu Aug 01, 2019 6:57 pm

Hi Bob,
Your numbers help tremendously. Since I have both of the other other engines, all I need to do is compare the .15 to them to see (hopefully) a difference between the biggun and littler ones.

Now to figure out why this engine ran only when the needle was about to fall out of the spraybar!

Ken Cook Thu Aug 01, 2019 7:10 pm

Jim, is the front collet ( carb body ring) tight? If the plastic body is leaking air, this could constitute the need to open the needle as far as you did to get it to draw fuel. The other would be that the needle is incorrect or not fitting the spraybar properly. Place oil on the threads and hold your finger over the venturi while turning it over. Watch to see if the oil gets sucked or blown off. The other issue is that seeing these spraybars are brass, they get a case of the green death inside of them. That thick gooey green mess which can cause enough blockage which doesn't break down immediately with no fuel. Really give it a work out with a piece of wire through it and in the center hole.

944_Jim Thu Aug 01, 2019 7:39 pm

Thanks Ken,

All good points. This engine was bought used, and looks to be used very little. The glow plugs kit bright, and smelled clean...no fuel residue burning off.

My mistake was taking an unknown engine and slapping it on a plane. I usually run an engine on the stand before using it. That has stopped building planes around worm out engines several times in the last few years.

My "fuel system" is also an unknown...some balsa with a fuel pipe and epoxy with a latex finger for a non-pressure bladder. This was a first for me. All my other models get hard tanks.

Once I determine the correct NVA is in it, then I will remove/clean the NVA. Then it will get benchrun, tached, and re-installed. I really want to see this engine fly on that plane once!

The one time it ran, I was shocked by the slower speed and bark it had compared to an .049! It just sounded awesome!

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Medallion .15 NVA nipple size

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