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Hiscott RC conversion needle

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Help! Hiscott RC conversion needle

Post  rhyslegge on Sun Jul 01, 2018 8:28 pm

Good evening!  Lately, I won an auction on the bay for a TD .049 w/ Hiscott RC conversion.  It was a used engine.  I proceeded to take a NIB TD .051 i had in my stock and install the used Hiscott carb. body/ throttle arm and muffler on my new .051.  No problems, fits great and I'm sure it will power the GLH to high velocity.  The problem is this:. The seller enclosed a new from CI Medallion needle valve and spring.  The Hiscott spray bar looks to be a stock Medallion unit, with a brazed on throttle arm and milled flats to form a throttle valve.  However, the threads on the needle valve shank out on the spray bar before the needle closes off fuel!  The threads fit, but the valve obviously isn't long enough.  Can someone out there with a Hiscott RC kit check the needle valve and let me know if it's a stock Cox unit or a custom Hiscott part please?  I appreciate the help in advance! Sorry for lack of photos, the engines are currently in my tool box in White Plains NY!
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Help! Re: Hiscott RC conversion needle

Post  1/2A Nut on Sun Jul 01, 2018 10:21 pm

The whole exhaust / throttle system was never made for a TD engine only Medallions.  
The muffler / exhaust throttle could be used on the TD but most TD have SPI
TD will loose power if you put that (particular) muffler on it. The design chokes
down quite a bit of exhaust pressure, retaining heat and loss of rpm. If you have
a TD cylinder with no SPI the muffler will be better suited. If your plane does not
require max power to perform well for you then it's a nice aesthetic muffler.
Note with the muffler flipped around the throttle pin can be pushed by a servo
for throttle without a RC carb. Or if left on the right side of the engine used as
a muffler with a RC carb currently available from EX Model Engines and Cox International.
You could put a Medallion carb body on the TD crankcase and move forward with the conversion.

Note the pic, I am showing just two small holes for the exhaust to travel past
the long header to get to the muffler. The throttle choke is in the natural open
position if pressed it does seal off very good. If you get it running post a vid
there are none for this on Youtube. Small Cox Logo




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Help! Re: Hiscott RC conversion needle

Post  rhyslegge on Mon Jul 02, 2018 9:39 am

If you get it running post a vid
there are none for this on Youtube.

I definitely will, thanks for the info! I knew that using this muffler on an SPI cylinder was less than ideal, I just didn't realize how much it would affect performance. I do have a NIB non-SPI cylinder assy. I could use, thanks for that! Unfortunately it's going to have to wait until I can figure out what needle it needs tho!
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Help! Re: Hiscott RC conversion needle

Post  rhyslegge on Mon Jul 02, 2018 10:37 am

1/2A Nut wrote:
The Medallion NV is used with the Hiscott system no doubt.

Here you can buy a brand new carb body to convert a TD to Medallion type.

https://www.ebay.com/itm/COX-ENGINE-049-Medallion-VENTURI-Carburetor-Original-Red-86-c0502/271091300895?rt=nc&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D52910%26meid%3Dbea692fcffc94aa5877034def6f00a33%26pid%3D100005%26rk%3D2%26rkt%3D11%26sd%3D271353791508%26itm%3D271091300895&_trksid=p2047675.c100005.m1851




If you want a Medallion engine there are always a few for sale on ebay.
https://www.ebay.com/itm/Cox-Medallion-049-Model-Airplane-Engine-W-Ex-/163124679137?_trksid=p2385738.m4383.l4275.c10

Medallion needle valve for sale:
https://www.ebay.com/itm/Cox-049-09-Medallion-Airplane-Engine-Needle-Spring-049-09/282342871495?epid=530313977&hash=item41bcf251c7:g:UD0AAOSwopRYjkLG

This is what it should look like:

I believe that needle is what was supplied with the engine when purchased. Is that the one that is supplied with the Hiscott kit? I believe I will buy another one and see if I have better luck, perhaps the one that I received had defective threads? Thanks again for your info and help!
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Help! Re: Hiscott RC conversion needle

Post  1/2A Nut on Mon Jul 02, 2018 10:41 am

Yes NV does not cost much worth a shot.
I imagine Hiscott used Cox stock parts to make it work.
NV does not need to close all the way to meter fuel to the engine,
typically it's turned out 1.5 to 2.5 turns for a running engine.As long
as the engine runs lean or rich when adjusting the valve you should
be good to go.

Small Cox Logo RC Plane Small Cox Logo
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Help! Re: Hiscott RC conversion needle

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