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-   -   Ironhead Best Carb for an Ironhead? (http://xlforum.net/forums/showthread.php?t=2079817)

Chuckthebeatertruck 21st July 2021 20:28

Quote:

Originally Posted by kitabel (Post 5906398)
He "built" a carburetor... out of an S&S carburetor. Didn't see his name on the casting.

It's called "modifying".


George Smith partnered with Leo Payne to take Leo's modified DC Linkerts and design a new, clean slate carb that incorporated the best of the Linkert principles with Leo's modifications.


The Smith's then produced the carb in series.


Leo was a racer, machinist, and tuner -- not a producer. George Smith was a producer.


It was a partnership -- and a very successful one at that.


Which is why Leo Payne and George Smith are in the AMA Hall of Fame.

Ferrous Head 21st July 2021 23:53

A new "clean slate" design ?

Seriously ?

Have a very good look at your DC and then check the L Series. Tell me that's not just an enlarged DC.

On that basis Doc Dytch designed new Sportster engines.

The poor Tilly that everyone decries got a bad (mostly undeserved) rap from the start when HD put the HD1A on a Sportster. It had a too small idle passage and the pop off pressure was set too low. I don't believe they ever sorted the pop off pressure but you can do that yourself.
It Probably should have come with the AM tickler as well but if you set the pop off correctly, add a tickler and an adjustable main you have a very good carb.
It was the carb of choice for the Harley Race team. Think about that. Came stock on XLR's.

Mind you, a CV is probably a better choice for a street bike (above all others) but I won't run them on my bikes.

11B40 22nd July 2021 00:33

Ever see the set up that uses a DC and a Servicar DC side by side? Looks great, probably doesn't work all that well. I'd bet that there is more to the two carbs than looks?

Ferrous Head 22nd July 2021 02:58

I have seen the dual Linkerts and my Mate, Bruce ran dual Amal's on his engine.

I think that what you pick up in being able to set the intake tract lengths to what you want/need you lose with the 90 bend in the intake.
And then you have doubled your carb problems. Not always a good idea.

The Dc's are big enough to feed the stock 900's. No accelerator pump but apart from that, they work well. I have a DC1L which came on the 58 CH engine I have.
But that's a big bore stroker now and too small.
The fact that HD persisted with them for 9 years might tell you something as well.
(Apart from them being cheap)

thefrenchowl 22nd July 2021 10:20

11B40, a servicar DC can't be used on a Sporty, it's got a venturi the size of your little finger...

To do a "reverse" DC, you need a std Sporty DC and remachine the venturi to race specs, one normal and the other one reversed, then side by side to get the float chambers on either sides:

https://i.imgur.com/We8iiXX.jpg

And surely, if your twin carbs come to a common chamber before your valves, I can't see the point... So it also needs 2 separate inlet tracks...

Chuckthebeatertruck, pretty good of you to show us picks of that seminal Leo Payne carb... But who's lucky enough to own it???

I'm a bit surprised at the 0.090 main jet size... I wonder if Leo wanted to keep some secrets away from his competitors... My MGAL shown below runs on methanol about right with a 0.177 main jet (4,5mm diameter) plus a bit more from an outside adjustable Mikuni jet (similar to a Tillotson main jet adjuster)

Air mix ratios in weight from gas to nitro are gas 13/1, methanol 6/1 and nitro 2/1 which would suggest a nitro jet for my MGAL would be about 0.300

I know there are 2 Leo Payne bikes about, how did they managed to lose this carb!!!

Gene, that's what a std gas MGAL looks like once moded for alcohol/methanol:

https://i.imgur.com/o3ZFewS.jpg

...If I was to tell you where the horn comes from, you'll never speak to me again!!!...

Patrick

Chuckthebeatertruck 22nd July 2021 14:21

Quote:

Originally Posted by thefrenchowl (Post 5906484)
Chuckthebeatertruck, pretty good of you to show us picks of that seminal Leo Payne carb... But who's lucky enough to own it???

I'm a bit surprised at the 0.090 main jet size... I wonder if Leo wanted to keep some secrets away from his competitors... My MGAL shown below runs on methanol about right with a 0.177 main jet (4,5mm diameter) plus a bit more from an outside adjustable Mikuni jet (similar to a Tillotson main jet adjuster)

Air mix ratios in weight from gas to nitro are gas 13/1, methanol 6/1 and nitro 2/1 which would suggest a nitro jet for my MGAL would be about 0.300

I know there are 2 Leo Payne bikes about, how did they managed to lose this carb!!!

Patrick

Ah, someone asks pertinent questions.

However, others on this thread have made it perfectly clear they know this carb as well as tying their shoes.

so I'll let them post their detail photos, their measurements, and tell you who is its keeper.

mrmom9r 22nd July 2021 15:21

https://live.staticflickr.com/65535/...b3a47731_k.jpgironhead 009 by don rothwell, on Flickr

thefrenchowl 22nd July 2021 15:34

Well, on my carb, it tooks the combined efforts of my friends Richard and Dr Dick to arrive at this methanol jetting... Basically, the more they drilled the main jet, the faster I went!!! So no bulls**t from this writer!!!

I'm in GB, but I believe both Leo's bike are now owned by the man sitting here on Turnip Eater, but I do not remember his name... He was Leo's last sponsor after Leo probably fell out with George...

https://i.imgur.com/o6AKn1P.jpg

Nice bowl extension, mrmom9r... No room for that on me bike, so I put an empty SU chamber in proximity.

Patrick

thefrenchowl 22nd July 2021 15:51

And in modern times, 2 fellas on the 2 bikes in question... I don't know who they are either...

https://i.imgur.com/gtCz7wU.jpg

Patrick

Akdawg 22nd July 2021 16:32

What a great thread ...thanks you guys! Back in those days I was putting together Triumph 500s for flattrack later 750 when they changed the rules in 69. The guys that were the tuners, and I mean real tuners, Dick Bender, Sonny Routt, Harry Penn, George Klein, were like gods to me. Out of the box thinking, LOTS of trial and error, were no computers to do the math - the experiments that worked, or didnt, things to marvel at. The only dynos available to mortals was the drag strip or oval track. Keep this history out there!


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