81 XS650 seizing bearing noise with hard braking

RZEEEE

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Picked up an 81 XS650 Special with 11k. Working on a budget restoration but have noticed a noise on hard braking, sounds like a seizing needle bearing. I've heard similar before in an RD350 that had low trans fluid from leaking CS seal. Or maybe cam bearings? Other? Fresh 15w45 Rotella oil non synthetic. Level is in the lower third of the sight glass on the center stand, didn't want to overfill per info I learned here, extra leaks etc. Engine is untouched & 40 yrs old. Tomorrow I'm gonna try putting more oil in it just to see if it changes but it shouldn't be happening at the current level imo. It seems likely braking is sending oil forward away from said bearing but because it only happens during braking, I havnt been able to isolate the exact source. At first I thought it maybe an odd interaction with front rotor/pads but rear braking produces the same... Ideas? Bike runs well with good power, fully rebuilt carbs(bs34's), adjusted the valves, timing chain, drive chain and clutch. Changed right case oil filter but didn't do the sump yet(?). No other significant mechanical noise, no modifications other than needles shimmed ever so slightly richer. Thanks for any and all experience or suggestions.

Steve
 

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It could. The noise is either on or off, no in between. It also happens during application of the rear brake only so I'm thinking likely not the brakes now but I'll try them on the center stand with front wheel off the ground, see what happens. Ran across another thread where clutch thrust bearing/washer was the culprit. Hadn't thought of that so clutch inspection in order, planned on it this winter anyway. Thanks for the suggestion SSSSSSlither!
 
It seems likely braking is sending oil forward away from said bearing but because it only happens during braking, I havnt been able to isolate the exact source.
Lift the rear wheel up to simulate oil being flung forward. My gut feeling is there's a good enough film that it wouldn't matter any longer than it takes to brake. Other possibilities are loose internals that get flung forward like cam chain, loose engine mounts, or the brakes themselves
 
happens during application of the rear brake only so I'm thinking likely not the brakes now
It only happens when the rear brakes applied..... yet you don't think it's the brake.
Not sure I get your logic. :umm:
 
It only happens when the rear brakes applied..... yet you don't think it's the brake.
Not sure I get your logic. :umm:[/QUOT
I wrote... "At first I thought it maybe an odd interaction with front rotor/pads but rear braking produces the same."
It happens ALSO when the rear brake is applied, eliminating the front brakes as the noise source
 
Lift the rear wheel up to simulate oil being flung forward. My gut feeling is there's a good enough film that it wouldn't matter any longer than it takes to brake. Other possibilities are loose internals that get flung forward like cam chain, loose engine mounts, or the brakes themselves

Interesting, I'll try that. Also agree The oil film should prevent noise from starting so quickly. It starts when I hit the brakes and stops soon as I release. It doesn't happen any other time and is literally on/off. As I said, this sounds exactly like a needle bearing seizing from lack of oil. Now I'm wondering if my imagined bearing isn't already on the way out thus reacting to oil sloshing more rapidly?
Ill inspect the clutch hub bearing and thick washer tho my instincts tell me that's not it... I've been wrong plenty of times b4. It'll show signs of seizure and/or overheating if it is. Clutch needs complete inspection anyway. Thanks for your ideas.
 
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