Some new Rotor / Torque info
1 reply to this topic
Posted February 16, 2003 - 02:21 PM
Well I did what I said I was going to do. This is the history on my bike. I had it about two weeks and couldn’t put more than 8 miles of slow riding on it due to very cold weather and snow. When the Torque scare came up I unscrewed the inspection port and checked the torque and it was 47#. I worked jetting it and making it street legal and ordered a woodruff key. When I heard of the shaft rotor tapers being off I decided to check mine and lap it if it was off. During this time I probably only got 10- 15 more miles on it but I was pushing it harder on dirt roads and doing mini wheelies with all the torque it has. There was lotsa snow and ice so I was cautious at this. I heated it up, drained the oil, replaced the oil filter but didn’t put the oil back in. The filter did not have any debris in it, much different than the first oil change on my 426. After getting the cover off I used a 15/16 wrench as suggested to hold the rotor and an beam type torque wrench to remove the nut. To my surprise the nut loosened at about 25#, not the 47 I measured earlier. I used a three prong puller and bought long 6mm bolts, removing three from the rotor to use with the puller. I was concerned with using such small bolts with the puller. I thought I might tear out the threads in the rotor. I recommend getting the correct tool, which pulls the rotor off the proper way. I wrenched little by little taping the end of the puller. I was at a point that I was going to quit, and I gave it one more wrench tightening and it POPPED off. Any more and I think it would have tore up some threads. I cleaned of all the oil on the rotor and shaft, and then wiped down with ether. I used a wide black felt tip and marked the entire taper of the crankshaft. After a short dry, I slid on the rotor with some force and moved it back and forth 6 or 8 times. When I pulled the rotor off I found that only half of the surface length was contacting. It was the rear larger area so it probably represented 60-65 % of the holding surface. That’s not enough for me. I re-marked it and put valve compound on the high area (the back half). You need to be careful because you could get compound in your engine, threads on the shaft, keyway slots, and some bearings in the area. I thought it would take quite a bit of lapping to get it to mate properly. But two trials just turning the rotor back and forth 6 or 8 times each trial and it the taper was clean end to end. I’d guess that I only removed 1 or 2 thousandths of an inch. I cleaned everything up used the new key and saved the original as a spare because it had no signs of stress. I torqued it to 47# with a double check with a second torque wrench. I plan to put 25 to 50 miles on it and re-torque it again. I noticed the manual says to check torque on the rotor bolt occasionally. I think that tapers that are not line to line, seat a little as you ride, this lowers the nuts torque value. Then when you push the engine hard, or it backfires due to poor jetting, or any other form of stress occurs, the taper grip lets loose and there goes MR Woodruff.