Really large M-53...

What are your thoughts on carb that's been modifyed like this? Any idea what it might have been used on?

Hi Epinut,

racing mod with alloy special venturi, it's illustrated in the KR/KRTT specifications & instructions manuals, drg number 1027-35RC, drawn 11th Sept. 1959, gives a 1"312 venturi size, carb throat 1"3/4

Patrick

Thanks Patrick!
Any chance that you could find the illustration on the net? Or if anybody that has it & could scan it, I'd really appreciate it.
Stefan.

Hi Epinut,

It has been on my site for quite a while!!!

http://www.harleykrxlrtt.com/images/0%20tech%20kr%20carbsm.bmp

Patrick

Thanks, I've even looked for it there but never found it...?
Stefan.

I wonder what type of jetting and passage way changes are need to use it? Seems like there would be less suction on the jet due to the larger diameter. Thus less velocity increase over the jet.

Anyone know?

44

Hi all,

The 1959 drg does not say what jets to use... but this venturi will make the mixture leaner.

A similar 1959 drawing covers the Linkert DC fitted on the XLRTT. There it says "use the 1957 XL number 9 main jet or drill the number 4 jet fitted with a number 51 drill (.067")"

Drg on my site is in the "Technical" page, click on "Technical info on KR/XLR"

Patrick

Appears to be 1-5/8" (1/16" oversize) on the throttle side, bigger at the air-horn. I've heard that the 4 bolt has been bored to take 1-11/16" throttle disc but never seen it. Going to 1-3/4" may expose the idle/transition passages.
That venturi was also available as a casting that extended out of the air-horn to form an extension.
Not only will this require richer main circuit, but probably a larger transition hole, and an intermediate hole in the main nozzle may help.