View Full Version : crank bearing

07-24-2015, 6:01 PM
after a full year of heartache, and no solution to my charging problem, i have found out just how freakin little i really know about triumphs. been doing the queens iron for 25 years, but this one got me. replaced the alternator, went thru 2 black boxes, two ignition systems, and the final result was a mechanical problem. went to replace the alternator one more time, and by sheer coincidence, found some heartbreaking play in the crank on the drive side. its enough to make a 'thunk" by jiggling the output shaft. the rotor beat the shit out of the inside of the stator. the bike ran like a guilty hood rat, but now that i know this, there were indicators.here is the question. can i split the cases, without removing the trans, cams, timing side stuff, etc? i have no problem doing that, but would rather not. can i just pull the top end, and the
drive side case half off and repair the damage done? i know the answer, but im hoping to be wrong, as that seems to be the better part of my lifes decisions.....

07-24-2015, 6:34 PM
The correct answer is .....split the cases.

07-24-2015, 7:22 PM
Not to mention flushing, blowing out then inspecting everything since the parts which powdered likely wandered through the rest of the engine and ya need to KNOW all is clean before reassembly.

I'd tear it down completely out of caution. A few more hours work but then you can put it back knowing it is sound. Don't skip anything. Wishful thinking never saved an engine part.

07-25-2015, 12:30 PM
Try a forged crank, there was a lot of flex in the older ones that put too much stress on the bearings, if a forged crank costs too much perhaps you can size up some roller bearings but make sure to find the torque stress values so the outer ring doesn't shatter if it flexes against itself with too much force.

07-25-2015, 3:23 PM
Any unit crank should be forged. I suggest visiting Triumph specialist forums for detailed best practice inspection and overhaul advice. There are plenty of parts out there. Don't forget to clean your crankshaft sludge trap.

These machines are now quite old so going conservative costs less and breaks less often but they will still be somewhat delicate. Do a total cost spreadsheet after you inspect everything and before ordering any parts so you can hunt the most cost-effective rebuild parts and services options.