Now here is the rest of the story:
The Fall and Rise of ‘Pa’s Transmission
On a beautiful Sunday afternoon in early August some fifty miles from home the layshaft bearing in my trusty (?) Norton’s transmission failed. With the kick-start lever pointed to six o’clock I knew that ‘Pa’ and I would be spending some more quality time in the garage, not on the road.
The initial teardown for diagnosis was just to remove everything from inside the case. The Portuguese bearing was in many pieces and scattered everywhere but the real disappointment was that one of the ball bearings had tried to escape thru the case leaving a crack below the oil line. This necessitated the removal of the case itself.
According to the manual removal of the case is another project in itself but after removing completely the primary cases and a little finagling the shell came right out.
A local machinist who builds, rides and races motorcycles did a great job welding up the case, it hasn’t leaked a drop in three hundred miles, all for only twenty-five dollars!
Parts were ordered from the East and West coast and from the Mother Land and I waited for more then a week for all the needed parts to arrive. Meanwhile I had a great time riding my son’s Honda CBR (I can ride any bike in the garage whenever I want to, its part of the maintenance agreement my boys have with the resident mechanic)
With some part in the freezer and some parts in the oven the rebuild had begun. My wife doesn’t even ask anymore, she just shakes her head when she goes thru the kitchen and I’m standing in front of the oven with a potholder and pliers. (I have a receipe for Shaft and Sleeve in the Half Shell if you’re interested) The sleeve bushing sent were not correct, too short, so I had to cut one of the old ones to length to fit in between the two new ones and act as a spacer.
This is really an easy job I told myself, I’ll be riding this very weekend. (NOT!)
I reassembled the gearbox without any left over parts and took ‘Pa’out for his first (of many) test drive. Everything went quite well, no unusual noises, shifts up smoothly….but
the shift lever went sort of limp after shifting into fourth and we limped around the block back into the garage for teardown #2.
“The knuckle end of the quadrant is aligned to top of cover stud” so says the workshop manual. This seems to be open to some interpretation and the picture is vague also. So after I shifted to fourth the quadrant went too far up and became disengaged from the ratchet plate and spindle. It took several tries with test shifting a partially assembled gearbox to find exactly the correct spot. Lesson well learned!
Test drive #2 was a nice Sunday afternoon ride with my two boys for a leisurely fifty-mile run out to the covered bridge and back and then a quick examination in the garage. Another setback, oil leaking from either the transmission or primary case and upon examining the oil level in the box I discovered the oil was full of “gold”, way too much bronze shavings then was called for in a rebuilt box.
The oil leak was diagnosed with a mirror and flashlight to be the inner seal of the primary case where the shaft from the clutch basket goes thru.
This is when I noticed that there seemed to be a lot of endplay at the kick-start shaft. Measured it was: 0.71mm or .02800in. this went clunk-clunk when pushed and pulled and seemed like too much.
Start all over again, strip the complete primary side off and gut the gearbox. I made up a spacer to check the clearance between the shaft and the hole in the inner primary case, the shaft has to be centered or the seal can’t do its job. Lesson #2 read all the parts of the manual, they covered this alignment problem in the book but I must have fallen asleep because the shaft and seal weren’t where they were supposed to be. I installed a new seal, loosened the support plates and bolts securing the transmission case and with a little leveraging all was fine on that side of the problem.
The gearbox was stripped and completely disassembled, every part was inspected and fitted to its mating part and inspected again. It seems that the kick-start shaft blind end had accumulated a large amount of shavings from the lay shaft bushing during the initial failure and this “gold” was now being recurculated. All the parts were taken to work and cleaned and rinsed in commercial washing solvents twice before reassembly. Then my son, the newly graduated Engineer, and I spread out the entire contents of ‘Pa’s transmission on the kitchen table (again the silent wife just shaking her head) and examined all the parts with a magnifying glass and flashlight. All parts passed inspection and the reassembly started again. By this time, if nothing else, I was getting pretty good at taken it apart and putting it back together again.
I made up some shims and installed them between the last gear on the layshaft and the inner race for the new bearing to take up the excessive movement and keep the race in place on the shaft. The new endplay measured was: 0.35mm or .01380in. This feels much better but then what do I know?
The final reassembly went smoothly and quickly. The job was inspected after a fifty-mile break in run and no oil leaks were found and only a miniscule amount of “gold” was seen in the oil. The oil was a little darker and the box hotter then I thought it should be( there I go thinking again) so I changed the oil and rode for fifty more miles and repeated this process four times then rode one hundred miles and now the oil has no “gold” and still looks like new . ‘Pa now shifts smoothly up and down.
Total for this job; $400 including towing,
transmission parts and a new primary chain,
Six weeks with ‘Pa’ out of service,
Over sixty hours spent in the garage, on the phone or online looking for parts and seeking information.
When I think I know it all is when I need the most help, and the more I know the more trouble it gets me. The Norton transmission is really quite a simple device, and I would encourage anyone with even only a little mechanical experience to take on a rebuilding job. Most of the problem I had were my own fault from being too cocky, not doing a perfect clean and inspect before assembly and interpreting the fuzzy direction myself instead of seeking advice from an expert.
A very special thanks to Stan Smith, Mike Taglieri, Dave Comeau, Greg aka norbsa and Hobot for their encouragement and willingness to share information with a stranger. I can only hope to some day repay the favor by helping another Brit-Iron rider.
Ride On
Dave
David Mathers
9/29/2004
