Best Carb For Ironhead
Early Sportsters (1957-1965) were fitted with side-float Linkert DC carbs, which were simple units to diagnose and repair. The Linkert DC was also found on other Harley-Davidson models, including the 1957-1966 Servi-car, and one-year-only (1966) Shovelhead.
Read: Linkert DC Carburetor Rebuild
For those of you who ride an early 900cc Sportster, it's a rare bird and you'll probably want to keep it stock. If you have the original Linkert, leave it in place. But for those who have a later Ironhead, there's better carb choices.
A switch to Tillotson was seen with the 1966 Harley Sportster and 1967 Shovelhead. Unlike the previous Linkert, it had an accelerator pump and featured a hydraulically operated automatic "economizer" circuit.
The Tillotson carb was complex and had many parts, and was not appreciated in its day. Lack of knowledge and poor parts availability tarnished their reputation, but when set up correctly, they are an excellent carburetor. The Tillotson Model HD was original equipment on Ironhead Sportsters until 1971, replaced by the simpler Bendix unit.
Originally fitted on 1972 to early 1976 Sportsters (and some Big-Twins), the Bendix carb is a popular choice for classic motorcycle builders and restorers who still ride their old scoots. They are relatively simple units that easy to tune and cheap to buy.
Read: Bendix Carburetor Rebuild
The three styles of Bendix Carb made for Harley V-twins are a 38mm fixed main jet (factory style), 38mm adjustable main jet, and 40mm adjustable main jet.
Shop: Bendix 38mm Carburetor (fixed jet)
Currently, you can still a buy a fixed, non-adjustable main jet 38mm Bendix carb. These carbs are designed to replace OEM 27155-72B and use a single cable throttle assembly. Many riders feel they are the best factory carb for Ironhead Sportsters.
The Keihin carbs found on Ironhead Sportsters are fixed-venturi units, not to be confused with the later slide-type (CV) carbs found on 1988 and up Evo Sportsters. The first two years of Keihin-equipped Sportsters had issues (early 1976-1977), but these were addressed and corrected by 1978. In 1979, venturi size went from 38mm to 34mm.
The Mikuni is a slide-type carburetor, also known as a CV (constant velocity) carburetor. Back in the day I was riding a 1972 XLCH Sportster, and other Harley riders used to mock my 40mm Mikuni because it was Japanese. But to my delight and their surprise, the bike started consistently on the 1st or 2nd kick.
The Mikuni sticks out from the motor more than the stock Bendix, and may give a slight obstruction to your right knee.
S&S Super E
When introduced in 1975, the S&S Super B was the carb to run. That was until the Super E came out in 1990, basically a Super B but with an accelerator pump. The Super E has a relatively small 1-7/8" bore, which allows greater air velocity, resulting in better low and mid-range response and power.
Shop: S-S Cycle Super E Carburetor
If you've modified your 1000cc Ironhead Sportster, consider a Super E. Please note that there may be clearance issues with S&S carbs on early Sportsters with magneto ignition.
S&S Super B
Although the Super E has gone on to become the best selling performance carburetor in the V-twin aftermarket, many riders still prefer the B over the newer E model, claiming it has better flow and more low end punch.
The Super B carb is not as forgiving to improper jetting as E carb, but it's my personal favorite carb for a 1000cc Ironhead. I ran one on a 1976 XLH, and the difference between the stock Bendix carb vs the Super B was night and day. I don't think it was ever designed to run on a "small" V-twin, so careful jetting is crucial.
Read: Tuning The S&S Super B
The SU was one of the first commonly available constant velocity "CV" carbs, and was a popular carb swap for Harley Panheads and Shovelheads in the sixties and seventies. These variable-venturi carbs were originally found on European cars, such as Triumph, MG, Volvo, and others.
Measured by bore size, common SU carbs are the HS2 (1.25"), HS4 (1.5"), and HS6 (1.75"). For a 1,000cc Ironhead, look for one with a 1.25" bore.
Because many classic cars were fitted with SU carbs, air filters are still available. You could also modify existing air filters to fit the odd 4-bolt pattern on the SU carb. This involves measuring and drilling holes in the backing plate.
There's not too much more impressive than a dual-throat Weber sticking off your bike, but these carburetors are very time-consuming to dial in, simply because there's so many variable factors, and one adjustment usually affects others.
Adjustable items on dual-throat carbs include main venturi size, main jet, idle jet, air corrector jet, accelerator pump jet, emulsion tube, fuel inlet valve, and air horns. A dual-throat carb on a Sportster may cause interference with the rider's right knee.
The Mikuni-Solex pictured here is a car-type carburetor, but is gravity-fed like most motorcycle carbs. This one came off a modified 1972 Sportster.
In 1984, Harley-Davidson introduced the XR-1000 Sportster, which featured a pair of 36mm Dell'Orto carburetors. With several other factory engine mods, power output was 70-horsepower. Weighing in at 490 pounds, the XR-1000 could hit 125 mph.
Read: 1980-1985 Sportster History
Fuel System Maintenance
If you have to store your bike for any length of time, untreated fuel may go bad in as little as three months. Longer than that, a fuel system cleaning is recommended.