Any guesses what is stuck in my crank?

[NONclow]

this crank might be rusty (old core, found another one), but this is how it came out (minus rust), these are balancing holes cast at the factory and finish balanced by hand for the weight of the con rod, bearing & pin.

Hope this helps

 

[NONclow]

Here are some of the (dirty) case. If you can pop that piece out, does it look like any of the case castings that might be compromised??

Or is it more like a bearing shell?

 

[Uncle Bryan]

Can you give us a couple more pics of the chunk that is in the sump.
Also, can you stick a mirror in thru the sump (at the con-rods) and tell us if all of the counterbalance holes (on each side of the con-rod) are open?

Please don't tell us what it is till we take a few more guesses at it
Sorry if that sounds mean ^^, but hey, we're guys, this is fun for us.

Edit: Oh wait, you already told us you have the top end off, so just look down at the counterbalance holes...that was stupid of me.

 

[shotgunjoe]

Could it be part of the transmission somehow?

 

[fullercameron]

Well I got the case split and got the crank out. Here are a couple of pictures of what I found.

It looks like there are two holes in the geared RS flywheel that are filled with something. The piece that found it's way between the flywheels looks to be one of these plugs that somehow worked it's way loose. You can clearly see the other plug in the last picture at the top part of the pic. To the left and below is the hole where the other plug came from.

I haven't prodded the plug that is still in place, but the remains of the one that has come loose seems very soft. I thought it was aluminum, but is it possible that it is actually lead or something else soft that was added as balancing to the crank? It appears that the plugs are only on the geared wheel. All of the other flywheels just have the standard two holes that are empty.

Does anyone know if this is something that was done on early model crankshafts or if this is some sort of modification that was done at some point?

Sorry the images are turned. Not sure how to re-orient them. Hopefully you get the idea.

I am hoping to pick up a spare engine this weekend and everything inside the case looks completely unharmed, so my hope is that the crank in the spare engine will just drop right in and I'll be back on the road.

At this point, I am really just curious if anyone has seem this before.
Thanks for all of the interest and guesses. Aside from the broken engine part, this has been interesting.

 

[TwoManyXS1Bs]

Holey filled holes, Batman! You have a real mystery there. Anybody hear of this kind of balancing experiment?

Fullercameron, not sure if you've experienced typical xs650 vibration, did this engine seem smooth to you? Normal early xs's would vibrate enough to skitter backwards on centerstand/concrete.

 

[shotgunjoe]

That pin in the flywheel looks very strange as well... wtf is going on? Another home made piuece I think. Typically one would remove weight to balance a flywheel, not add a soft material that can work loose. Never cease to amaze me, the things one will find done to an old machine.

Is it just my imagination, or is the rod pin in the wrong hole, and the 'weight', in the hole the rod pin is supposed to be in?

 

[hotdog]

Weren't the early 256 cranks "corked" in the some of the flywheel holes with aluminium..? I beleive I have read this somewhere.?

 

[racerdave]

Weren't the early 256 cranks "corked" in the some of the flywheel holes with aluminium..? I beleive I have read this somewhere.?

It was common in the 70's and maybe prior, to cork 2 stroke cranks, to try and change case volume. Never seen it on a 4 stroke.

 

[hard_y_rd]

Here's a pic of my 73 256 motor. I wasn't sure if i had any pics or not. Don't know if this helps.

 

[hard_y_rd]

Another pic.

 

[TwoManyXS1Bs]

Yeah, if you look closely at hard_y_rod's starter gear flywheel, looks like something in there. I've had 256 (`70-71) and 306 (`72) cranks, nothing in the flywheel holes. This one (`73 - 336???) seems to have something in there. New to me...

 

[fullercameron]

So it is hard to see, but it does look like there may be a similar plug in hard_y_rd's crank.

Just for reference, this wheel has 5 large holes. Shotgunjoe, in the last image, the top and left holes are the "plug" holes (the one on the left being the escapee), and there are two smaller holes on either side of the rod pin, and then the pin itself. The holes with the plugs appear to be essentially opposite of the open balancing holes.

As far as vibration, the bike seemed to vibrate like it was supposed to. This is my only XS, but it never felt exceptionally smooth to me. It did a good job of buzzing the mirrors.

 

[fullercameron]

I am hoping to use a different crank to get the bike back running, but does anyone know how or if this one can be salvaged? The hole that the plug came from seems to be chamfered and the remaining plug is finished flush to the surface of the flywheel, so I assume that these plugs were cast in place somehow.

 

[Brian902]

Hugh would be your man to ask about the aluminum plugs in the crank webs. He has seen enough cranks to know if these were common and what years they may have been used. I've seen these in 2 stroke cranks used for performance gains but not familiar with them in 4 strokes.

Your crank is rebuild-able so removing the plugs and getting Hugh or someone to check it over and rebuild would be easier than getting a used one and going through the same process.

My suggestion: PM Hugh.

my 2 cents.

 

[TwoManyXS1Bs]

Double-up on Brian's 2 cents. This may be a transition crank, when wristpin went from 22mm to 20mm. The latter rods are easier to get. Measure your wristpins, if 22mm, this could get expensive...

 

[fullercameron]

The crank is a '72 as far as I know. It does use the larger 256 pins and pistons.

Like I said, I had already arranged for a spare engine and I am hoping that the crank will be in spec so I can just swap it in and run it at least for the rest of the season. I'll take a close look at the new crank and see if it matches up to this one. The spare I am picking up is also a '72. I guess I will also do some close inspection of these plugs in the new crank if they are there.

I figure the crank can be rebuilt, my question is whether these plugs should be replaced somehow, or if when the crank is rebuilt they should both be removed. I don't really have a good handle on the physics of these engines and it seems like removing weight from one flywheel would cause some problems with imbalance.

I'll contact Hugh and see if he has seen these plugs. I was hoping he might see this and chime in since he is definitely an experienced crankshaft guy, but I also know that he has his hands full with his shop right now. I thought if I have to rebuild this crank, I may use the spare motor parts for a rephase, but first thing's first - gotta get this back together so I don't have to roll around in my truck w/ no AC all summer.

 

[NONclow]

I've heard with some of the early electric start #4 flywheels, when they cut the starter teeth it was lighter, hence drill holes and fill with lead and balanced.

You could reuse if recast w/ lead and machined/balanced

.......Or, good luck with new crank, and enjoy the paperweight

 

[Brian902]

Now the question becomes:

Why did the plugs get loose?

Too many heat and cool cycles?

A vibration caused by something?

I suspect these don't loosen up too easily and not very often, so what caused it?

 

[Punkskalar]

Well I got the case split and got the crank out. Here are a couple of pictures of what I found.

It looks like there are two holes in the geared RS flywheel that are filled with something. The piece that found it's way between the flywheels looks to be one of these plugs that somehow worked it's way loose. You can clearly see the other plug in the last picture at the top part of the pic. To the left and below is the hole where the other plug came from.

I haven't prodded the plug that is still in place, but the remains of the one that has come loose seems very soft. I thought it was aluminum, but is it possible that it is actually lead or something else soft that was added as balancing to the crank? It appears that the plugs are only on the geared wheel. All of the other flywheels just have the standard two holes that are empty.

Does anyone know if this is something that was done on early model crankshafts or if this is some sort of modification that was done at some point?

Sorry the images are turned. Not sure how to re-orient them. Hopefully you get the idea.

I am hoping to pick up a spare engine this weekend and everything inside the case looks completely unharmed, so my hope is that the crank in the spare engine will just drop right in and I'll be back on the road.

At this point, I am really just curious if anyone has seem this before.
Thanks for all of the interest and guesses. Aside from the broken engine part, this has been interesting.

Those are OEM flywheels, have not been modified by someone. They came that way from the factory, and the loose slug you see is a lead based filler put into the holes. I assume it was to try and balance the early engines a bit better. We see them fairly often, I have never seen one come apart nearly that far however The later model cranks did away with this, and we've seen no difference in vibrations honestly. I know that when we rebuild those particular flywheels, we heat up the lead to a molten state and "press" it back into the recesses in the flywheels.

But yes, that is an OEM 72-73 crank from what I can see here. Was it running when that happened? Thats awesome!