discovered mag ring to flywheel magnets is at .016".
Can't yet detect endshake on crankshaft by turning/pulling/pushing, so .016" may be as close as it gets.
I know that .025 - .040 is desireable clearance. Am I at significant risk wearing thrust collar on rear main in next few 1000 miles?
this is a sweet running barn find '13 (runs on mag well) which I am converting to Kevlar bands. After 2000 miles, the old cotton brake band was starting to unravel on one end. Otherwise all bands were in great shape. Hate to go to Kevlar and give up silky-smooth pedal engagement, but want safe, reliable touring. Magnet clearance was a surprise and wonder if it might have been rebuilt to that clearance in the past, since I can't detect end shake on crank.
Scott, With the hogs head and pedals off the transmission, and the hand lever disconnected, the clutch spring is energized so it's kind of tough to push and pull on anything to see if the crankshaft is in fact moving back and forth due to wear of the thrust surface on the third main. You will probably have to go to the front of the engine and use a cheeter bar as a lever at the crank pulley to push against the crankshaft and "over ride" the clutch spring enough to see if the crankshaft does indeed have a lot of lateral play. Someone correct me here if I am wrong! ....Michael Pawelek
Pull the pan inspection cover so you can pry the crank forward and aft to measure endplay. If the gap gets no closer than .016" and the car runs good on mag I certainly would keep driving.
You may want to think about only using the Kevlar band lining material on the brake. Cotton low and reverse bands last a long time and will give smooth engagement. Kevlar on the brake band will give you better braking.
Michael, Your wrong! (you told me to tell you). With the hogshead off, the clutch spring is no longer attached to anything, and therefore is not putting any tension on the crankshaft, etc. The clutch spring is only compressing the clutch discs inside of the brake drum.
Scott, Most all the wear is on the front side of the third main bearing because when the T engine is in neutral, the clutch release bearing is compressing the clutch spring towards the rear of the engine, and therefore "pulling" the crankshaft to the rear of the engine. 95% of all wear on the third main bearing thrust surfaces are on the front of the bearing cap (which can allow the magneto gap to get larger). Yes, .016" mag clearance is pretty close, but not unheard of. Insert a prybar or large screwdriver between the front crank pulley and the engine front cover and pry the pulley forward (all you should need is maybe about a 10-15 pound pull on about a 12" prybar - don't go nuts and bend anything). If you still have your .016 clearance, you probably will not have any problems for a darn long time (maybe thousands of miles). Use an API certified regular 10w30 or 10w40 detergent motor oil to provide the best wear protection. If you want to correct the problem without pulling the transmission and magneto, you could replace the third main cap.
thanks to all.
thanks for your input on kevlar. I was in fact thinking of just that (doing brake only), because the old cotton looks almost new on low pedal and reverse (and they're so smooooth during operation) and rivets are nowhere near surface of cotton, though I know for certain that it's 30+ years old.
I'd never heard of anyone just doing one kevlar and others cotton, so wasn't sure if it was a dumb thing to do. I couldn't find cotton so defaulted to Kevlar because it "seems to be the thing to do". I think with care, cotton should last for years and years of modern driving, though now that everything is open, it's probably smart to at least reline the brake with Kevlar as you suggested.
One more question...cotton is about 3/16" thick. Is this still as "new" as I think, or was the cotton originally a lot thicker, and I'm just kidding myself?