Bike just seized up! 78, xs650e

David Mansure

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XS650, 78, 23k miles, no mods. I just rebuilt the carbs, tuned it. Was running great. Started bike last night, was at idle in the garage. Then I heard a "CLUNK" and it just stopped...seized up. Cant turn the rear wheel, can't even kick the kick starter!!!!!!! It has plenty of oil. Cant imagine what happened. Anyone have any ideas?
 
Obviously, something has come adrift. Being as there are so many bits and pieces inside, it could be anything. You could remove the right cover and check everything in there, remove the valve covers and check in there, remove the plugs and have a look in there, but realistically there are a million things it could be.
 
Valve came loose, made contact with piston?:shrug: Have you removed valve covers to check for irregularity? Depending on how it happened, may roll backward via rotor nut...
 
I'd drain the oil, remove the clutch cover, and see if something happened to the oil pump or its drive arrangement. Next, remove the clutch pressure plate and clutch plates. Now the engine and gearbox is separated, and you can identify where it locked up. In any case, the engine will have to come out of the frame and be disassembled.
 
Most likely causes that I can think of -
1. Rocker arm adjusting screw locknut backed off, and now the screw or the nut jammed between cam lobe and head casting.
2. Valve spring broke/keeper somehow came loose and you dropped a valve.
3. Some part of the shifting mechanism under the right cover came apart and jammed into the primary gears. However, the crank on the right side spins clockwise, so debris would have to somehow be lifted UP into the gears.
4. Cam chain broke and is now wadded up in the bottom of the crankcase jamming the crankshaft.
5. Anyone feel free to add to this less-than-comprehensive list.

My '76 had been apart by someone before me and I found many sins internally. You don't know what kind of gorilla had his dick beaters in your internals over the last 44 years. Let's just hope it didn't cause too much damage.
 
I'd drain the oil, remove the clutch cover, and see if something happened to the oil pump or its drive arrangement. Next, remove the clutch pressure plate and clutch plates. Now the engine and gearbox is separated, and you can identify where it locked up. In any case, the engine will have to come out of the frame and be disassembled.
yup, Thats this weekend's project
 
Most likely causes that I can think of -
1. Rocker arm adjusting screw locknut backed off, and now the screw or the nut jammed between cam lobe and head casting.
2. Valve spring broke/keeper somehow came loose and you dropped a valve.
3. Some part of the shifting mechanism under the right cover came apart and jammed into the primary gears. However, the crank on the right side spins clockwise, so debris would have to somehow be lifted UP into the gears.
4. Cam chain broke and is now wadded up in the bottom of the crankcase jamming the crankshaft.
5. Anyone feel free to add to this less-than-comprehensive list.

My '76 had been apart by someone before me and I found many sins internally. You don't know what kind of gorilla had his dick beaters in your internals over the last 44 years. Let's just hope it didn't cause too much damage.
Ill find out this weekend for sure
 
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