Cam chain or what?

[Jim J]

I am new to the forum and hope to rely on it to help over time with my XS2 project. I acquired the bike to keep my old retired hands and mind occupied and am sure this bike will do that. I was told the bike had been idle for the last five years. No known history other than that. I figured I'd try to get it to run before disassembly. The previous owner had kicked it over to demonstrate the engine was free. I removed the plugs, kicked it over a about three times, checked the cam chain adjustment, checked for compression, had none on either cylinder. Thought I'd check the valve adjustment. The left exhaust valve is bent, big time open.While turning the crank there were areas of resistance and in fact when I got to TDC for the right cylinder the crank reversed direction on its own by about 10 degrees. Is this due to a binding cam chain or what? It will likely be some time before I remove the engine to tear into it and until then I am really curious as to what I am in store for. Thanks

 

[Jim]

Welcome to the forum!! There's a few of us here working on our "retirement" project
No compression and a bent valve sounds suspiciously like a broke cam or cam chain that either jumped a sprocket or broke.

 

[Jim J]

Welcome to the forum!! There's a few of us here working on our "retirement" project
No compression and a bent valve sounds suspiciously like a broke cam or cam chain that either jumped a sprocket or broke.

 

[xjwmx]

Take a valve cover off and see if the adjuster goes up and down when you turn the engine over. That will tell you a lot. Hopefully nothing is bent really. Front right valve cover is easy to strip, so careful.

 

[Jim J]

Thanks for the reply Jim. The valves open and close ( except for the stuck one) and they are closed at the appropriate TDC's, so I think the chain is for now intact. But the crank rotation is jerky and wants to reverse direction as indicated. ??

 

[Jim]

Ok... I see where you're at now. The open valve might not be bent. It might have spent the last 5 yrs. open and has rusted in that position. Try squirting your penetrating oil of choice into the valve springs on that valve and on the valve stem inside the cylinder.... multiple times a day for a day or two and see if it will work it's way loose. Careful about spinning the motor while the valves sticking out. Just gentle rotations. Rusty/dry cylinders might be the compression problem also. When/if you get the valve unstuck, squirt some motor oil in the cylinders and retry the compression check.

 

[Jim]

But the crank rotation is jerky and wants to reverse direction as indicated. ??

Now that could be chain related. If it's rusted, the links could be binding.... Was the motor left open (any covers off) during it's 5yr. storage?

 

[Jim J]

Now that could be chain related. If it's rusted, the links could be binding.... Was the motor left open (any covers off) during it's 5yr. storage?

The covers were on it when I got it. I'll try penetrating oil on the valve stem as you suggested, lube up the cylinders, and see what happens. I'll let you know. I wonder if the chain picked up sufficient lube to help it while I kicked the engine over. ?? Checking out the chain will obviously have to wait until the engine's out. Thanks.

 

[5twins]

If that valve is stuck open enough, the piston may be hitting it as it comes up. That could stop rotation, and maybe reverse it. Get that piston on the cylinder with the stuck open valve way down on it's stroke, like down near BDC. Then you can try knocking the stuck valve in with a soft punch (brass) and hammer. If it's just stuck from corrosion, that may break it free and it might snap shut for you then. If you can get it to bounce in but it won't come back out all the way then it probably is bent.

 

[xjwmx]

You have two cylinders with no compression. I think the least likely reason is two bent valves or one bent and one stuck valve. Then most likely reason is two stuck valves. Of course it could be anything at this point. I would dump the motor out on the floor and open it up. A pallet comes in handy,

 

[Jim J]

You have two cylinders with no compression. I think the least likely reason is two bent valves or one bent and one stuck valve. Then most likely reason is two stuck valves. Of course it could be anything at this point. I would dump the motor out on the floor and open it up. A pallet comes in handy,

Thanks everyone for the input and ideas. Regardless of what's going on I feel somewhat assured by your experience and willingness to help. I'll find out after disassembly. It may not be for awhile but I'll refer back to this discussion and post the results, and likely will have another question or two.

 

[TwoManyXS1Bs]

...when I got to TDC for the right cylinder the crank reversed direction on its own by about 10 degrees. Is this due to a binding cam chain or what?

... But the crank rotation is jerky and wants to reverse direction as indicated. ??

Welcome to the forum, Jim J.

When the pistons are near TDC:

One cylinder is at its fire point, its valves are closed and not pressing on the cam's lobes, since they're pointing downward.

The other cylinder is between exhaust and intake stroke, known as overlap, since the exhaust valve is almost closed and the intake valve is opening. The valve springs are applying sufficient reactive force to the cam to rotate the engine.

When the camchain is stretched, the equidistant lobe position is retarded, and will want to rotate the crankshaft forwards to where both valves have the same opening.

This is a natural phenomenon, and a fair indicator of camchain stretch.

FYI, mine's stretched, and will also rotate the crankshaft forwards about 10°...

 

[Jim J]

Welcome to the forum, Jim J.

When the pistons are near TDC:

One cylinder is at its fire point, its valves are closed and not pressing on the cam's lobes, since they're pointing downward.

The other cylinder is between exhaust and intake stroke, known as overlap, since the exhaust valve is almost closed and the intake valve is opening. The valve springs are applying sufficient reactive force to the cam to rotate the engine.

When the camchain is stretched, the equidistant lobe position is retarded, and will want to rotate the engine back to where both valves have the same opening.

This is a natural phenomenon, and a fair indicator of camchain stretch.

FYI, mine's stretched, and will also rotate the engine back about 10°...

Thanks for the welcome 2M, and thanks for the explanation. Thought provoking and makes sense.