Best Carb For Ironhead
Early Sportsters (1957-1965) came 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 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.
The three styles of Bendix Carb made for Harley V-twins are a 38mm fixed main jet, 38mm adjustable main jet, and 40mm adjustable main jet. Many riders feel they are the best carb for Ironhead Sportsters.
read Bendix Carburetor Rebuild
The first several years of Keihin-equipped Sportsters had issues (early 1976-1977), but by 1978 these were addressed and corrected. The Ironhead Keihin carbs are fixed-venturi units, not to be confused with the later slide-type (CV) carbs found on 1988 and up Evo Sportsters.
The Mikuni is a slide-type carburetor, also known as a CV (constant velocity) carburetor. Way back in the days when I was riding my 1972 XLCH Sportster, other Harley riders used to mock my 40mm Mikuni because it was Japanese, but it worked very well. To my delight and their surprise, the bike started consistently on the 1st or 2nd kick.
S&S Super B and 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. 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 and G models, claiming it has better flow and more low end punch.
read Tuning The S&S Super B
There's not too much more impressive than a dual-throat Weber sticking off your Sportster, but exotic carburetors are very time-consuming to dial in, simply because there's so many variable factors, and one adjustment usually affects others. The Mikuni-Solex pictured here is a car-type carburetor, although it is gravity-fed like most motorcycle carbs.
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 will cause interference with the rider's right knee.
The Effects Of Ethanol Gas
Ethanol is used in today's gasoline as an additive, and E10 gasoline today contains roughly 10% ethanol. Ethanol has a shorter shelf and tank life than gasoline, and can begin to break down in as little as three weeks. Another problem with ethanol is that it attracts water and "breaks down" faster than gasoline.
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Ethanol is the same type of alcohol that is found in an alcoholic drink, which works somewhat like a cleaning agent - not good for an older engine. It also increases vapor pressure in gas, which may cause vapor lock in the carburetor. These issues are not so bad with daily transportation vehicles, but with small engines not driven regularly they are problematic.
Proper Gas Storage
Make sure that you store your gasoline properly and try to use it in a timely fashion. Use a product like Sta-bil and add it as directed. This will help prolong the life of the gas and keep it from harming your engine.
Fuel System Maintenance
If you store your bike over the winter, untreated fuel may go bad in as little as three months. Longer than that, a fuel system cleaning is recommended.
read Motorcycle Storage Tips
Octane Requirements (rule of thumb)
- 80 octane for 8:1 or less compression motors
- 90 octane for 9:1 compression motors
- 100 octane for 10:1 compression motors
Only in theory are carburetors are simple devices.