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8N Marvel Carburator

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Michael P. Desl

04-16-2003 16:46:37




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One more for you - the tractor has a Marvel Carburator on it. There are two fuel adjustment screws on the side facing out. I found this link:

Link

Which says each should be turned out about onew turn - is that correct? The large screw on mine was out about four turns.




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Dell (WA)

04-16-2003 18:11:47




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 Re: 8N Marvel Carburator in reply to Michael P. Deslippe, 04-16-2003 16:46:37  
Michael..... ...each and every carburator adjusts differently because each engine is different. 1 turn or 1-1/2 turns gets you kinda in the "ballpark".

Adjust the idle mixture (small side needle) for MAX IDLE rpm's NOT smoothest idle. Set idle speed to slow 400-450 rpms with throttle setscrew on backside of carb. (its a back and forth proceedure)

BIG front mainjet sets MAX POWER at MAX rpms UNDERLOAD. I sett'em at 2 turns and leav'em. Check sparkie color after using for a while, should be tanish/greyish, NOT SOOTIE BLACK. Soft sootie is sign of TOO RICH, lean'er 1/8 turn. White sparkie insulator is sign of TOO LEAN, tweak'er 1/8 turn for richer mixture.

Carburators are BLACK MAGIC, and I know all the incantations (grin)..... ....Dell

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Michael P. Deslippe

04-17-2003 13:02:44




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 Re: Re: 8N Marvel Carburator in reply to Dell (WA), 04-16-2003 18:11:47  
That's great - thanks!

Until I get my manual, I'm working in the dark.

I've been working on cars since 1963, so these things aren't foreign to me - but the tractor ius definately old technology.

Do these things have problems eating unleaded gas?



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no . . . Dell (WA)

04-17-2003 13:34:09




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 Re: Re: Re: 8N Marvel Carburator in reply to Michael P. Deslippe, 04-17-2003 13:02:44  
Michael..... ...N-Engines came from the factory with hardened exhaust valve seats. And the low compression flathead engine was designed for 75 octaine gasoline..... .BUT..... modern no-lead gasoline needs a hotter sparkie to prevent fouling. Autolite AL-437 is popular, equiv to Champion H-12, (OEM was H-10)..... ..Dell



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Larry, Mo

04-17-2003 07:10:33




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 Re: Re: 8N Marvel Carburator in reply to Dell (WA), 04-16-2003 18:11:47  
Excuse my dumb question, but, if I need to lean the mixture, do I turn the big screw in or out?
Thanks for your patience.



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Dell (WA)

04-17-2003 09:08:49




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 Re: Re: Re: 8N Marvel Carburator in reply to Larry, Mo, 04-17-2003 07:10:33  
Larry..... ..generally accepted convention, in for lean, out for enrichment. Do it in 1/8 turn increments and observe the results. Go operate the tractor doing what ever for 15-30 minutes. Turn off the engine and pull a sparkie, look at the color of the center insulator. Sooty black, too rich, clean white, too lean. Looking for light gray or light tan or light yellow..... ...Dell



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Why do you think......bg

04-16-2003 18:38:32




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 Re: Re: 8N Marvel Carburator in reply to Dell (WA), 04-16-2003 18:11:47  
...they call 'em Marvels?



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