Engine Rebuild Part III - Crankshaft Rebuild

The Royal Enfield Interceptor crankshaft is a heavy duty assembly. It is dynamically balanced which was not common for its day. The rods are substantial and the bearings are well designed for their job. The Interceptors are known as smooth running machines due to the attention paid to this assembly.

The crankshaft is out....time to rebuild. 

One thing I was a little concerned about was the sludge trap as the caps can be difficult to remove on most British motorcycles. I have heard many people drill and use an EZ out to overcome the stubborn little buggers. I was hoping I would not have to resort to that.

So what is the sludge trap? It is a cylindrical cavity in the crank center that collects the tiny metal shavings that flow through the oil ways. I did not expect to get much out of the RE as the engine looked pretty good inside. I was wrong about that as sizable chunks of rusted steel particles were found. This reaffirms the notion that cleaning the sludge trap is a "must do" when the crank is out. My RE has only logged 12,993 miles yet the collection of metal bits was pretty substantial. My BSA Hornet, which had a severe life, also had blobs of steel wool looking material inside the crank. After thoroughly cleaning the trap the caps were reinstalled, staked into place, and secured with Locktite.

The Allen wrench wouldn't budge it....my manual impact driver didn't move it......

The air impact easily popped both plugs out with minimal damage to them. 

Well this doesn't look like something I need in my crank....little metal bits rusted back into a solid.

Cleaning out the sludge trap with a 12 gauge bore brush.  

The bearings looked good but while I had the engine apart I decided to replace them. 

The crankshaft journals measured within spec and were not ground. The connecting rods were bead blasted and reinstalled with new "nominal" sized bearings in the caps. The small end bearings also measured within spec and will run on new wrist pins. The rod cap bolts were torqued and safety wired into place. Loctite was used for additional insurance. 

Safety wiring the rod bolts with stainless aircraft safety wire.  

Reassembled, wired, and ready to go into the cases...time to build up the lower engine unit. 

Grandpa Ken in England  in the early 40's. He is second from the left in front of a bomber with a very politically incorrect name. 

Engine Rebuild - Part II - Crankcase Teardown

The Series II Interceptor crankcase was a new design for '69 and had features that differed significantly from its predecessor. The engine was now a wet sump design with varying oil pressure between the head and crankcase. The points moved to the forward section of the timing cover and the oil pump moved aft. These changes gave the engine a new look making it easy to differentiate from its predecessor and other makes.

A new design for '69. A real beauty. 

The Interceptor's engine and transmission layout also stood out from others. Triumph and BSA used a unit construction design and Norton carried on with its separate engine and transmission layout. The Interceptor used a semi-unit design which tasked the engine to be a section of the frame.

Cooling fins on the lower cases are part of  the Series II wet sump engine design. 

Royal Enfield advertising touted the craftsmanship and performance of the Interceptor that set it apart from other makes. Several of these features were found in the crankcase; a dynamically balanced crankshaft, camshafts that could be swapped without splitting the cases, and wired connecting rod bolts clamping numbered rods and caps together. An optional oil cooler was designed to reduce engine temperature under heavy use. A great idea for an air cooled twin. The Interceptor was a premium motorcycle.

Semi-unit gearbox and engine design. The Albion transmission is bolted directly to the the engine. 

The oil filter and cooler. A well constructed unit. 

The chain driven dual cam setup remained for the SII's new design and the dual plunger oil pumps were replaced with one. To the dismay of mechanics a timing cover oil seal retainer was not included setting up the engine for a potential oil pressure loss. This is frequently discussed by Series II owners and several methods to add a retainer have been developed. I took the advice of my peers and fixed this weakness on my Interceptor. The upgrade was detailed in a previous post.

A mechanical marvel with a mile long chain.  

Readily removable camshafts for the race tuner. 

The plunger oil pump....very unlike my A65 BSA's. 

The engine tear down offered no surprises except for an aluminum chip which was found in the oil sump. It appears to be casting flash. The cases were difficult to separate which was caused by rusty location dowels holding them together. I worked gingerly with a wood clamp, a screwdriver, popsicle sticks, and a pine block. PB blaster, my old friend, loosened gaskets and dowels up a bit. Great care was taken not to mar the castings. After the cases were separated it was on to inspecting the internal bits. Although in need of rebuilding, no significant problems were found.  

Using a reversed wood clamp and several other tools to open the cases. 

Getting there.....soaking in solvent for a bit. 

Inside the cases...things look pretty good. 

Rusty dowels made splitting the cases difficult. 

 

The neat bits inside....wired connecting rod bolts speak performance to me. 

Numbered rods and caps show an attention to detail.

The manual calls for 1/16 inch spacing on the timing side bearing .....as measured is pretty close. 

Time to clean, inspect, and rebuild the crankshaft. 

A follow up to my last post. Another photo taken while "Grandpa Ken" was on an extended trip across the pond in the early 40's.