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Title: s u carb Post by: Firery Fred on January 09, 2014, 09:24:21 AM Fancied trying an su carb on my xs, someone piped up that they were available, albeit years ago, for bikes , ie smaller. Anyone any ideas ?
Title: Re: s u carb Post by: Olds on January 09, 2014, 09:53:33 AM Smallest SU that I know of is the 1 1/8" used on very early Sprite. Should imagine they would be hard to get in good condition.
Would have thought that 1 1/4" (32mm) as used on Reliant 850 and a lot of other small cars could be used and easier to come by. Title: Re: s u carb Post by: Dslam on January 09, 2014, 10:52:09 AM Have a look at this link from Burlen fuel systems who reproduce new SU carbs.
Triumph 6T Thunderbird from 1951-56 used an SU (MC2 type) http://sucarb.co.uk/carbspec/carburettor/spares/id/2504/ If the linky not working just copy and paste. Hope that helps. Title: Re: s u carb Post by: Olds on January 09, 2014, 11:12:34 AM That's interesting. It's an 1 1/4" SU for motorcycles, with lever choke.
Title: Re: s u carb Post by: morrag on January 09, 2014, 01:03:35 PM Get your self an as fitted to 'Mini', or similar 11/4" SU, make up an adaptor flange, and bingo! I have done it several times before,over the years, after all, a carb. is a carb. is a.........if you get my drft!The mid 50's did see Triumph use a purpose built SU on their Thunderbird's, but not for too long.I'm using a larger, probably too large! SU on the 500cc Honda GL motor for my 3 Wheeler, but we shall see how it performs, ;D ;D ;D ;D...Morrag
Title: Re: s u carb Post by: morrag on January 09, 2014, 01:11:00 PM I have attached a pic to illustrate! ??? ??? ???...Morrag
Title: Re: s u carb Post by: Manky Monkey on January 09, 2014, 07:34:35 PM There's a guy on Ebay who makes cast aluminium casings & manifolds for XSs.
I bought a pair of inlet manifolds from him to fit Amal carbs to mine, (2nd one down on the left). He makes them to fit an SU to an XS, (3rd & 4th down on the left). Cast stuff (http://www.ebay.co.uk/itm/yamaha-xs650-big-finned-exhaust-clamps-chopper-bobber-cafe-racer-custom-engine-/261352892230?pt=UK_Motorcycle_Parts_13&hash=item3cd9d8a746) Title: Re: s u carb Post by: Firery Fred on February 02, 2014, 07:08:36 PM Thanks everyone ,my mate has one that might be coming my way,when we can agree a price that I can afford. It's the smallest I've seen but of unknown origin , so we'll see
Title: Re: s u carb Post by: kapri on February 02, 2014, 09:05:30 PM On a normal carb venturi affects air velocity = fuelling and pick up . SU is variable venturi so will only rise as far as air requirements though too large a starting point will affect low end torque . Using an SU on a 500c revving to 10,000 then best size woudl be something used on a 1000cc car engine as same CFM requirements to be met at 5000 rpm.
Title: Re: s u carb Post by: Firery Fred on February 06, 2014, 10:56:23 AM He's had this carb on an XS and it ran great once set up correctly
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