Technical Articles

The ThreeBond Knucklehead—Part #1

THE OBJECT of this three-part series is to assemble a brand new Knucklehead engine using the best parts available and at the same time to demonstrate the advantages of using ThreeBond products for all the sealing and thread locking requirements. The Knucklehead engine—arguably the most handsome Harley engine ever produced—was chosen for this buildup because it is quite a complex engine with a lot of potential oil leaks and therefore an ideal candidate for the ThreeBond product range. This is a joint venture between Redgrave Motorcycles and ThreeBond Australia and all the parts necessary will be sourced from the extensive inventory held at Redgrave Motorcycles.

Although all the parts necessary are available to build the Knuckle as an EL (1000 cc overhead valve engine first introduced in 1936), a capacity of 74 cubic inch was settled on for various reasons which will be pointed out during assembly. In this issue of Ozbike we will build a suitable 74 inch flywheel assembly and get it sealed up into the cases; Part 2 will then move onto the timing gears, cam, oil pump, etc; and in our final issue we will install the top-end.

A cherry set of Genuine Harley-Davidson wheels were selected as the foundation for this flywheel assembly and are only pieces of the engine that are not brand. They are the last 74 inch wheels produced by Harley and were fitted as original equipment in 1972 through 1980 Shovelheads. They feature the larger taper in the driveside wheel to accommodate the updated sprocket shaft and are also slightly lighter in overall weight than the pre-1970 wheels.

When H-D introduced the large taper sprocket shaft in 1972 it was already two generations longer than the original equipment Knucklehead shaft due to electric start and then alternator commitments. Fortunately Jim’s Machine makes the correct length shaft for this conversion, and when installed provides the strongest version of this flywheel assembly available. Pinion shaft is also a Jim’s item incorporating 1958-and-up, right-hand main bearing which were used with only minor alterations through to the end of the Evolutions.

Conrods are new Knucklehead/Panhead units set up with an S&S crankpin and big-end bearing assembly complete the lineup of components needed to complete this tough flywheel assembly.

After final assembly and truing, the crank will be installed into a set of state-of-the-art S&S Knucklehead cases and sealed up with ThreeBond 1104 liquid gasket for the perfect leak free joint. As you can see this is shaping up to be a beautiful engine.

This completes the first stage of the ThreeBond Knuckle. In the next issue we will choose a cam and an oil pump and install them along with all the timing gears and related parts.

Feature by Richard Nicolls at Redgrave Motorcycles.

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