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Retrofitting the needle valve in your 40+year old COX product engine.

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Retrofitting the needle valve in your 40+year old COX product engine.

Post  balogh on Wed Jun 03, 2015 3:34 pm

Not a big deal but I thought I will share this with you. I am certainly not the first one to experience that notwithstanding the otherwise excellent mechanical condition (compression, balljoint, crankshaft fit etc.) of your old 049 (mine is 051) reedie, the beast does not want to do peak rpm and often goes into an erratic and  lean run that you do not want to ever occur for fears of excessive cylinder/piston wear.

This happened with my 40+year old critter pictured below, and I tried to do everything possible to mend the weak performance (including the replacement of the original horseshoe backplate with that of a new Surestart) before I did 2 things:

1. I removed then CA-glued back the black spray-bar seal on the spray-bar end to make sure it is really sealing air-tight ( I noted that the old and brittle seal was already turning around the spray-bar end freely, certainly allowing unwanted air intrusion under it)
2. I pulled a silicone tube over the spray-bar seal so that it covers the needle valve stem too to some length. This silicone tube not only keeps the needle valve thread - a bit lose after many years of use - airtight, but holds the needle fixed vibe-free and stress-free better than a stock spring does.

So I not only saved the original stock backplate and carburetor for further (eternal)use (you do not want to discard genuine components on an old engine responsible for your obsessive hobby) , but also gave the COX a new life.

The critter now runs 18k with a 5x3 COX prop as original and thankfully purrs at 100+dB in confirmation of the feasibility of the above retrofitting...
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