A Royal Enfield forum for the people

[Mrunderhill1975a]

I'm sure you all recall my rotor explosion that snapped the left crank spindle on my '99 Bullet 500. Originally, I planned to tear down the engine, remove the crank, separate the flywheels then remove the broken crank spindle and replace it with one from across the pond. While I was waiting for the crank spindle, I instead tried to drill and tap the broken spindle, which has thus far worked well for about 4000 miles now.
However, I am concerned that at some point, I will have to bite the Bullet and remove the crankshaft . This has caused me sleepless nights thinking about what I could foul-up by taking the engine apart. So, in preparation, I have been looking for a good description of the correct procedure. I stumbled upon a PDF of an out of print book from 1986 printing that describes vintage motorcycle restoration process. It describes several procedures that would minimize foul-up situations. My first concern is making certain the rebuilt crank, fly-wheel, and spindles and on the same axis. I can envision making a mistake and have the crank out of whack and start vibrating like a Bronco. You can see from the diagrams the problems that could occur. One way to stave off failure is by scribing a line mark across both flywheels to have a reference mark for reassembly. This reference mark would not guarantee the proper alignment upon reassembly, but would give a good start.

[Mrunderhill1975a]

The 1986 out of print manual procedure continues to describe the flywheel alignment procedure by constructing a home-make wooden jig as shown in the diagram below (Provided by Triumph Motorcycles Coventry Ltd.. (The crank assembly could more precisely fixed between the centers of a large lathe). Unfortunately, I have no such lathe.

The crankpin should be pressed or bolted up, firmly to one flywheel. Then fit the other flywheel ensuring the scribe marks on the flywheels line up correctly. Then tighten the big end eye nut about 3/4 tight. Using a magnetic dial gauge, as shown in the sketch. Radial run-out of one flywheel or the other can be achieved by the scribing shown earlier. However, in the event that the shafts appear to be revolving in a "skipping rope" fashion, this can be corrected by either a bump with a lead or brass hammer in the appropriate spot, or by gently pinching the flywheels in a vise or gently spreading the wheels with a wedge. Not much pressure is needed so don't get Arnold Swartzenager. It would be great if the lash was Zero when completed but, that is nearly impossible. A total runout of 0.001 inch is great.