Oh No!! I've got a big problem!

[DeanR]

If a crank bearing is shot, what are one's options? and would tiny brass colored specks in the oil point to this - with a motor that won't budge?

[John]

laxdad

Those flecks could well be bearing material. Try to pick them out of the oil with a magnet. They should be non magnetic. They are softer than the crank, so the crank should be ok, unless the bearing has spun, then the crank journal could be trashed.

[TopCatGr58]

Hey John and Shawn,

Shawn said that the engine was stuck, so it won't turn over any further in the normal CW(from left side) rotation of the crank! But, he may be able to turn the engine backwards, (CCW from left side)? IF so, then he shouldn't loosen the cam chain tensioner just yet. He should try to rotate the enginen backwards and then see if he can rotate the cams and get the alignment dots to show up top, and then verify that he can rotate the engine forward and backward enough to then turn the cams 180degrees dots down. Then he can loosen and remove the 1st cam sprocket bolt, then rotate the cams to dots up and loosen and remove the remaining sprocket bolts.

THEN he could loosen and remove the tensioner which would then allow enough slack to be able to pull the chain up and off the sprockets so he can then slide the sprockets of the shoulders of the cams. Then he can loosen the cam bearing cap nuts and remove the cams completely. Then, with both cams OUT, inspect to see if all of the valves are up!? And if so, then he can try to rotate the crank around, just have the cam chain looped with a firm wire or such to allow it to slide along as the crank is turned. There should be no worry about hitting the valves with both cams out.

Then, IF the crank will turn over and over, then he can tell that the bearings haven't been fried and that it was probably a skipped cam chain sprocket, and binding on an open valve. He can then pull the head WITHOUT necessarily having to pull the whole engine to replace any bent valves. But if the crank still won't rotate fully, then he can probably realize that he'll need to pull the motor for a complete disassembly and diagnostic!?
T.C.

[DeanR]

John, Just tried a magnet and these flecks DO stick! and lots of them. No engine knowledge. Could you briefly explain "spun" bearing and "crank journal"?? Thanks. Wondering about dismantling this engine over the winter both to find out what's wrong and also just for the education. Sorry about borrowing this thread a bit, but it is kinda the same basic topic!

[randy]

To answer your question laxdad;


Crank or rod bearings are made of soft materials, usually tin and copper. They are held in place by keyways in the bearing caps. the bearings have corresonding flanges that fit into the keyways. This is what keeps them from spinning in their bores.

When starved for oil, the tin layer of the bearing will wipe off first, then the copper. If they heat up enough, the motor will sieze. At the moment of siezure, the bearing flange fails and the bearing spins 'cause it's welded to the rotating part (crank).

This is known as a 'spun bearing'. It's all bad.


Other than the main and rod bearings, I am not aware of any other parts in the crankcase that contain copper (guys chime in here). the cams don't have bearing shells.

The only way to know for sure that this is your problem is to split the cases to get to the bearings.

[petejw]

I agree with TC,try and turn the motor backwards,
im sure it would b bent valves, and compared
to the worst type of scenarios, bent vavles would
be the easiest to repair.
the symptoms sound the same as mine did,
i was able to turn the engine backwards tho.
if the motor is totally seized in that u cant turn motor
either way, remove the cam chain tensioner if the chain
is worn u may be able to lift the chain from the cogs
without removing the cog bolts, not 100% sure tho.
i was able to turn the engine backwards with a spanner, with the tensioner
removed this allowed the chain to jump the cogs which allowed
the engine to rotate. would not normally recomend this
but u have nothing to loose at this stage.
i hope i made sense.

[wingnut]

New /old engine?

Shawn, I went down eastand looked at that 79 standard today. The bad news is living by the sea in a leaky old barn is not good for metal things. The corrosion on this machine is very heavy. Beyond anything I have the stuff to try and bring it back with. The good news is that the bike only has 13K miles on it. If your bottom end is trashed this could be the answer. The guy that has it will let the whole bike go for $100 It would be the only XJ around here with a kick starter thats for sure. If someone can help me out with the how to I'll post a picture of it.

[Shawn27530]

I'll take it

Thanks alot, That sounds good, did you try and kick it over?

I would like to go ahead and get it. Pm me yours or his phone number and I will come and pick it up. Its sad that is all rusty though.

I am going to finish pulling the cams on the XJ today. I can't rotate the engine either way, so I am going to have to grind a 10 mm wrench so I can get to the lower cam gear bolt. I did remove the tensioner and that was no help at all.

[skids]

Re: I'll take it

I have one recommendation. Put the bike on the center stand if you pull the cams. If it is on the side stand, the bottom slack can cause the chain to come off the crank sprocket and chain guide. It is just one more thing you do not want to deal with! Once the cams are out (use a couple of sticks through the cam chain to keep it from dropping into the cavity), you will be able to tell if you have bent valves by the heeights of the shims.

Originally posted by Shawn27530
Thanks alot, That sounds good, did you try and kick it over?

I would like to go ahead and get it. Pm me yours or his phone number and I will come and pick it up. Its sad that is all rusty though.

I am going to finish pulling the cams on the XJ today. I can't rotate the engine either way, so I am going to have to grind a 10 mm wrench so I can get to the lower cam gear bolt. I did remove the tensioner and that was no help at all.

[Shawn27530]

I got the motor to turn back to its 3/4ths turn one way and 3/4ths turn the other, that helped me to get the cams out. All the valves are closed as they should be, so no bent valves, cam chain was still on the crank sprocket. So the problem is internally, I looked down the spark plug holes all 4 pistons are moving up and down. I also dropped a cam cap nut down in the motor, luckily it landed perfectly on top of the crank sprocket and I got lucky with an extendable magnet and go it out.

So, I am going down to check out/pick up the XS11 that wingnut hooked me up with. So can I run the XJ11 carbs on the XS11 motor? Everything else is the same right. It will be cool with me if I have an XJ with no YICS. I will just call it the XJS1100.


"The bike was running when I parked it" Yeah right!!! I ABSOLUTLY HATE A LIAR.

[2bhappy]

Just throwing out wild guesses, maybe a spun rod bearing?

Marc

[Shawn27530]

Yeah Marc, thats what I'm thinking too, thats the only thing it could be at this point, there is nothing else standing in the way.

[prometheus578]

there is nothing else standing in the way.

Au Contraire.... If it was a spun bearing... why does it rotate for a while and stop. I mean... if it spun and siezed, either it wouldn't spin or it would spin all the way around.
Here's a fun thing to check for that I encountered once. Engine would spin one way and stop, and then would spin the other way and stop. Pinhead doing his own tune up, and working on other things at the same time dropped a screw into an open plug hole and didn't notice it!
You've got the plugs out. Get a flashlight and look in the holes as you move the pistons up and down. If this is the case, you may be able to see the screw(or whatever),imbedded in the crown of the piston, where it then hits a valve stopping the movement. Just a thought. (stumped me for a while, too)

[fxrer]

Shawn

As Randy explained earlier, a “spun” bearing is the result of excessive heat which “welds” the bearing to the crank, and thus spins it, either in the rod or main journal. A spun bearing would not allow the motor to move at all, not even ¾ turn. Don’t ask me how I know this!

Plus, if the motor ran OK before the PO parked it (assuming he is not lying), it is unlikely anything would cause the bearings to spin.

And, since the bike has low miles, I would doubt it is a bottom end problem.

Maybe something fell through the spark plug hole, into a cylinder?

I’m with pggg on this one. I’d pull the head for a look see on your motor, before I’d consider swapping for the other “used” motor. You don’t know what shape that motor is in either.

Try to eliminate the simple stuff before you resort to major transplant therapy.

[fxrer]

Prom, I posted before I read yours.

Great minds think alike!