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Sportster Motorcycle Air intake, Carburetor, EFI, Fuel, and Exhaust Problems, advice and/or how tos for Sporster and Buell motorcycle carburators, Electronic Fuel Injection (EFI), Air Intake, Fuel and Exhaust.

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View Poll Results: What would you use on your sporty for performance?
Mikuni HSR42 69 71.88%
S&S Super E 27 28.13%
Voters: 96. You may not vote on this poll

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  #51  
Old 15th September 2018
Four Speed Four Speed is offline
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Yes, a tuners trick back then was to play with the oil grade to affect the acceleration. Bit like an accelerator pump.
As I recall 20 weight was the standard grade dashpot oil. You could also get different damper valves that made even more difference.
If you fitted an SU to a smaller engine you would go for the lighter damping and vice versa. They were very rewarding carbs to play with.
Ah nostalgia.

Maybe there should be an SU carb thread.
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  #52  
Old 15th September 2018
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One thing I do think about is American vs Japanese. But then I face the fact that Mukini has the research to have ruled for years.

I answered Mikuni, because I have never really had an issue with one.
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  #53  
Old 15th September 2018
45Brit 45Brit is offline
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Define “performance”.

S&S were/are basically developed for drag racing, a sport with very limited following outside the US. Some very good people spent a lot of time and money developing road racing and flat track engines, and S&S came nowhere in their thinking.

I don’t dispute S&S were superior to the archaic Linkerts and Tillotsons, or the Keihin butterfly carbs which were not much more advanced.

The Mikuni cv carbs were a “next-generation” carb for a “next-generation” engine, the Evolution, which was designed to make best use of them.

For me, it’s the round-slide Mikuni, a solid little gem still with us today, along with its imitators such as the Amal Mk2.
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  #54  
Old 17th September 2018
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Quote:
Originally Posted by 45Brit View Post
Define “performance”.

S&S were/are basically developed for drag racing, a sport with very limited following outside the US. Some very good people spent a lot of time and money developing road racing and flat track engines, and S&S came nowhere in their thinking.

I don’t dispute S&S were superior to the archaic Linkerts and Tillotsons, or the Keihin butterfly carbs which were not much more advanced.
Seriously? S&S carburetors have been produced in no fewer than 7 different models-- from "shorty" units to "long venturi" types (some of which were actually designed for drag racing). But, to paint the whole line with the broad brush of being "drag racing" specific, is to display your ignorance and to ignore the experience of many American (and European) Sportster and Big Twin Harley owners who have gotten good broad-spectrum performance from these carbs. If the correct carb is used in its proper application (S&S is more than happy to help out with this selection, either by phone or on their website) they have been proved to be efficient and competitive-- if asked nicely, they might even help you shave some seconds off your dirt-track times.
All this being said, I still prefer the Keihin CV40 for street use on my Sportsrer, but that's a personal choice, and I don't belittle your choice for your application. However, I was not aware that Mikuni made a CV (constant velocity) unit. I guess ya' learn somethin' every day.
Joe
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  #55  
Old 18th September 2018
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Quote:
Originally Posted by JacksBrother View Post
Seriously? S&S carburetors have been produced in no fewer than 7 different models-- from "shorty" units to "long venturi" types (some of which were actually designed for drag racing). But, to paint the whole line with the broad brush of being "drag racing" specific, is to display your ignorance and to ignore the experience of many American (and European) Sportster and Big Twin Harley owners who have gotten good broad-spectrum performance from these carbs. If the correct carb is used in its proper application (S&S is more than happy to help out with this selection, either by phone or on their website) they have been proved to be efficient and competitive-- if asked nicely, they might even help you shave some seconds off your dirt-track times.
All this being said, I still prefer the Keihin CV40 for street use on my Sportsrer, but that's a personal choice, and I don't belittle your choice for your application. However, I was not aware that Mikuni made a CV (constant velocity) unit. I guess ya' learn somethin' every day.
Joe
Well said Joe, I ran an S&S super B back in early 1980's on a 98 cubic inch kick start only Shovel, that had a cast in air bleed.
later I got an S&S D that I drilled out and tapped a thread to use an S&S main jet, so I could change the size of the air bleed. was a really good kick start carb, as no excellerator pump to flood when kick starting. made good power too, these days I like the CV.
I've also had S&S shorty, S&S duel throat, S&S L series to name a few, they are all good but I did not keep the duel throat long.
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