Butterfly Carburetor Upgrade
Mike RoenDescription
The top end of our 1988 Heritage Softail Evolution motor is completely assembled. Mike is now moving forward to complete assembly of the rest of this Harley. The original butterfly carburetor and rubber compliance intake fittings that came with this motorcycle will not be reinstalled. These carburetors were on the first generation of Harley-Davidson Evolution motors. They performed marginally at best. These carburetors were never acceptable for performance applications. Therefore, it is very common to see first generation Evolution Harleys updated with a 40mm CV, an S&S Super E, or a Mikuni carburetor.
Mike is going to be upgrading this Evo butterfly carburetor with a 40mm CV carburetor that is known to be a good take-off from another Harley-Davidson. Mike has already disassembled, cleaned, and rebuilt this CV carburetor. The carburetor has also been jetted accordingly for the application. The choke or enrichener cable has also been replaced. Mike explains that it is always better to reuse the original metal choke cable nut if possible. Replacement cables come with a plastic nut that easily strips out prior to being snug.
The next generation intake manifold will also be used along with front and rear intake flanges and intake seals. A high-flow air cleaner assembly will be installed with a reusable air filter element and the original butterfly carburetor air cleaner outer cover will be used to retain the original look of this classic Evo.
Prior to installing the top motor mount, Mike mounts a new VOES (vacuum operated electric switch) and a choke cable mounting bracket. This small bracket was fabricated to mount onto the top motor mount and support the choke cable for the replacement carburetor.
Mike explains how and why it is important to properly orientate the top motor mount assembly. There are a number of things to consider, including fuel hose routing, horn wire routing, VOES wire routing, vacuum hose routing, choke cable routing, and positioning.
More on VOES:
Harley VOES Test
Harley Speedometer Cable Lubrication and VOES
Evolution Softail Exhaust System Removal