6 of one and half a dozen of the other.

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mcbob
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Vintage Karting items owned: Everything Mac but a Kart but who know's ?
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6 of one and half a dozen of the other.

Post by mcbob » Mon Oct 01, 2007 10:32 pm

Another day another question ??

What advantage would a Tillerton HR have over a Mac BDC except possibly spares and diaphrams ............

Mc Bob.

Rob Voska
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Re: 6 of one and half a dozen of the other.

Post by Rob Voska » Tue Oct 02, 2007 12:00 pm

With all due respect to Steve. After 30 years and being a half fast engine builder. I'm not smart enough to figure out a mac carb. :o I have some that work great :?: ....and some that don't :?: . And I can't figure out why.

I think of it more as a consistancy thing than anything else. Can I get a mac carb to start and run......yep....not much of a problem.......can I get them to "work" on any type of a consistant basis.....forget it!

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steveohara
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Vintage Karting items owned: 1969 Bug Sprint Mc 91B1
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Re: 6 of one and half a dozen of the other.

Post by steveohara » Fri Oct 05, 2007 4:14 am

Rob,

So true.... the one real advantage to the Tillys, whether it be two small or one big one it that they are pretty user friendly and consistent. I can usually make a BDC model carb work very well but there are still occasions where I have problems with them and they need a lot of attention. For a runner in the hands of the average vintage karter who only runs a few times a year the Tilly is just a lot less trouble.
Regards,
Steve O'Hara

Gordon Duax
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Re: 6 of one and half a dozen of the other.

Post by Gordon Duax » Thu Oct 11, 2007 4:26 pm

On the flow bench, the Mac carb is better, but I have to agree on the inconsistency point about them.
Too many little passages that can be effected by a small stray drop of oil, or atmosphere conditions.
And the needles seem to be much more coarse.
That is, they can go from rich to lean with less of a turn than the Tillotson.
If you want flow, let me build you a annular ring venturi HR (or find one that the late Jack Green made).
It gets rid of the booster venturi, and the 12 annular jets do a way better job at atomizing the fuel.
This is especially important on our little 2-strokes that have only inches between where the fuel dumps in, and where it's burned.
The ones I do have a one piece inlet bell, that extends all the way in, and forms the venturi.

Or if you have access to a machine shop, build one your self.

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