Technical Articles

The ThreeBond Knucklehead—Part #II

NOW THAT the crankcases are sealed up we can move onto the second stage of the ThreeBond Knucklehead build-up.
We need to select all the timing gears, oil pump and drive gears, the breather valve, the camshaft, and all the necessary spacers, clips, keys and shims. All these parts are new and come directly from the Redgrave Motorcycles inventory. The only exception is the oil pump and this is a genuine, cast iron, H-D original in mint condition. This was chosen over a new billet aluminium pump for a few reasons. Firstly, the Knuckle does not suffer from lack of oil, and with the addition of the 1972-and-up oil pump drive gear set, this pump will perform an exceptional job for our healthy Knucklehead. The second reason is that the cast iron pump looks right at home on this otherwise stock appearing engine.

Photo 1
Cast iron oil pump and all the components required for the installation.

Photo 2
Gasket in place, and with the oil pump shaft and bushing thoroughly lubricated, the pump is slipped into place.

Photo 3
The late model oil pump drive gear is installed and the pump is tightened down and checked for smooth operation before it is meshed with the pinion shaft drive gear.

Wherever possible the engine is upgraded with components that were developed by H-D to improve the durability of their engines during the long period over which they evolved. The pinion shaft is a good example, and because of the H-D practice of not changing anything more than they need to, this is an easy move. A 24006-58 pinion shaft was selected and it gives us some useful advantages. It has the 1.250” journal for the right hand main bearings which is what S&S have chosen for their cases. The shaft relies on a taper for the pinion gear instead of the earlier splined setup. This is a far better setup with more precise cam timing and much quieter operation. The only downside is that the cam cover needs to rebushed to accommodate the smaller journal on the outer end of the pinion shaft.

Photo 4
Components in order of assembly ready to be slipped onto the upgraded pinion shaft. Left to right are: oil pump drive gear and its key, spacer, late model pinion gear with its key, and finally the special pinion gear nut with left hand thread.

Photo 6
Removing the early model pinion shaft bush in the cam cover.

Photo 7
Line reaming the new bush in the cam cover.

With all the pinion shaft components in place the breather valve can be installed. It will need to be checked for end-float and timed with the crankshaft before the cover is put on permanently.

The next step is to install the intermediate gear and the generator drive gear. These will need to be installed and checked for end-float. Once the end-float is calculated shims can be selected and put aside for final assembly.

It is now time to trial fit the camshaft. It will need to installed with the proper gasket and the cam cover tightened to the correct tension. End-float, depending on which book you read, is to be from .001” to .005” and we shoot for around .004”; this is quiet and safe.

Various grinds of cams are available for the Knucklehead engine from stock replacement to high performance monsters. The cam chosen for the Knucklehead engine project is an Andrews ‘N’ grind, basically a modern version of the stock cam with .348” lift and 270 degree duration @ .020” This is an ideal choice; it is quiet, with plenty of power and is totally reliable.

Photo 9
The Andrews cam, Torrington bearing, thrust washer and the spacing shim which comes in a full range of sizes to set the cam end-float to our desired .004”

Photo 10
Cam bearing being installed with Redgraves’ tooling to prevent distortion of these thin wall bearings.

Photo 11
Timing marks are all aligned on the completed cam chest, after a generous lube, the gasket and cover can be installed for good.

Photo 12
The installation of the lifter-blocks and cam-followers is very straight forward as all these high quality parts fit and work together beautifully. These new Knuckle lifter-blocks have been treated to a coat of the Standox silver to match the oil pump and the cylinders. The cam-followers and tappets are Jim’s, the gaskets are James, and the locknuts are Colony.

Photo 13
Knuckles have longer exhaust followers than inlets. As long as the long followers are installed in the extreme outside bores and plenty of Rowe assembly lube is applied, this part of the job is very straight forward.

Photo 14
New 74” cylinders, S&S pistons and rings, James Gaskets and Colony hardware will be used.

Photo 15
Just before the pistons are installed, the little-end of the conrod is checked with a long wristpin against a special plate bolted down to the cylinder base studs. This will ensure that the wristpin is perfectly square to the bore.

Photo 16
Piston ring end gaps are all checked.

Photo 17
Spiro locks are used to retain the wristpin. These are just wound key ring style and seat nicely in their groove when correctly installed.

Photo 18
With the front cylinder in place, it’s just a matter of finalizing the rear cylinder to bring us to the conclusion of part 11 of the Threebond Knucklehead engine buildup.

Photo 19
The completed short engine is ready to have the cylinder heads installed. This will require quite a lot of work as the Knuckle rocker boxes and their many related parts are complicated and labour intensive. Between now and this time next month, we should have a coat of the beautiful Standox silver on the brand new heads ready to start on the final stage of the Knuckle.

Watch the newsstands for the next issue of Ozbike for the final instalment of this three-part series where this short engine will be topped with its unique cylinder heads.

Feature by Richard Nicolls at Redgrave Motorcycles.

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