Broke the engine?

[xs650newb]

Hey everyone,

Just finished rebuilding the engine. Took it for a 2 mile test run yesterday, put it through all the gears and began the break-in process.

Go to warm the bike up today. It kicks over no problem. The bike is idling for maybe 30 seconds and I hear the most awful CLANK sound and the bike dies.

Go to kick it again and the pistons have no compression. I can turn it over easy by pushing my hand on the kick start.

HERE IS THE WEIRD PART:
I went to take a look at the valves and none of the valves move when I kick the bike over OR when I put a socket wrench to the rotor.

The only thing I can think of is that the cam chain snapped.


Adam

 

[Reid]

Sounds like the timing chain let go

 

[xs650newb]

Does that mean it snapped or it fell off the sprocket?

Any way to confirm without pulling the engine? Can I remove the tensioner unit and get a peak inside?

Adam

 

[pamcopete]

xs650newb,

I think you can see the sprocket on the crank if you remove the sump plate.

 

[Paulrxs650]

Cam chains come adrift. Pop the head off and pop another on

 

[xs650newb]

Damn.

So a new cam chain cam off of a freshly built engine? Should I pop another one on and assume it wont happen again or is their an underlying cause?

Adam

 

[retiredgentleman]

Have you removed the sump plate yet as Pamcopete suggested ? Drain the oil and only 6 bolts to remove. Use a mirror....................should be a clear view of the crankshaft camchain sprocket and chain.

 

[xs650newb]

I'm gonna do that now. Need maybe 30 minutes...

 

[Tim of DO THE TON]

What kind of cam chain was this? Master link? Endless? Was the tensioner adjusted? Stock cam?

You'll need to pull the engine to replace the chain, so might as well get going on that now. If you want to avoid pulling the head off / replacing the head gasket (which you might be stuck with anyhow as once you release the compression on the gasket you should replace it) you could peek inside the cylinders through the spark plug holes to see any evidence of valves impacting with pistons.

When you turn the engine by hand, are you saying it turns over freely? No pistons hitting valves?

 

[jetmechmarty]

If the chain broke, and there's no compression, there are probably bent valves, correct?

 

[Tim of DO THE TON]

I would think so - but the valves could also simply be 'stuck' in an open position given the cam isn't turning. I don't know off hand if there is a possible position for the cam to be in, with 1 valve on either side open slightly, and not impacting the piston movement.

Would be the 1 in 1,000,000 chance of the chain breaking in that particular spot. Of course you also have the issue of the cam chain being all over the engine internals - where is the broken bit, if it's broken kind of thing?

If my cam chain broke I'd tend to pull the engine and take the entire thing apart.

 

[pamcopete]

Well, he said that it was easy to turn over with no compression. Not likely that the cam chain broke with all four valves open, in fact I don't think that is possible, so could be something else in the bottom end came loose. I would certainly check every possibility before removing the head.

Could be something in the clutch or primary gears, which may be repairable in the frame.

 

[xs650newb]

Well the problem has been identified atleast. The camchain snapped.

I drained the oil and attached to the magnetic oil drain bolt was this little piece.




My guess is that it is the master link but I haven't yet confirmed it is not some other piece on the cam chain.

What gives? The engine was just rebuilt and the cam chain is brand new.

When I started the bike up yesterday I ran it for 5 minutes before realizing the cam chain tensioner was super tight. I adjusted it then went on a two mile run.

Could those 5 minutes of idling stressed the chain to breaking?

Best,
Adam

 

[weekendrider]

Someone didn't rivet the master link together well?
Can you pull the chain out the bottom?
Not that it matters. A total tear down is the next step.

 

[xs650newb]

Ok. So I know what is going on. Just not the exact cause.


Mast link on the cam chain broke off. When I turn the engine over there is no compression BUT on the left side air comes out of the carburetor and on the right side air comes out of the exhaust.

I checked the valves and at the exact moment of breakage the left side had the intake valve open and the right side had the exhaust valve open.

Anyways, I gotta do a full tear down now.

I just pulled the remainder of the cam chain out through the sum plate. Is there any way AT ALL to put on a new cam chain without splitting the cases?

Best,
Adam

 

[weekendrider]

Did you find the other side plate and piece of link pin?

 

[xs650newb]

No I did not.

It is either in the oil that was drained out (sitting in a container at the moment) or stuck in the little filter I hope.

I guess all metal shards should be accounted for before the bike is fired again?

Adam

 

[Tim of DO THE TON]

The stock cam chain is an endless model installed at the factory. It's looped around the crank, and the tensioner is actually built around it.

Replacement chains are more or less always a master link style, given the need to completely dismantle the engine and grind out the tensioner bracket to install a new endless chain.

I replaced my first cam chain with a master link style, and paid a shop to rivet the link. It was all sourced from known manufacturers (I think you can use a Honda CB450 cam chain master link if I'm not mistaken). It's still in one piece. 2000 miles in I replaced the entire engine with a 750 rephased race motor I built. On that one I installed an endless cam chain.

I just tore down my old engine to clean it up and rebuild it. I'm installing another endless chain, but the one I had riveted originally is still in good shape.

Where did you get the cam chain / master link? How did you rivet it on?

Splitting the cases on an XS650 motor is not the big deal it might seem. It's actually really simple, and gives you an opportunity to replace all the seals and ensure an oil tight leak free engine.

If you have all the parts on hand, I'd suggest you can tear down and re-assemble an engine in a couple days no problem. If you spend time cleaning it (i.e. soda blasting the cases etc.) then that would stretch it out.

Worth the effort in my opinion. I'm in the middle of my 2nd tear down / clean up / re-assembly.

 

[Tim of DO THE TON]

Oh and I got my endless cam chains on Amazon for like $16. Don't overspend on them. Just Google the cam chain specs and you'll find them for sale. I bought 2 at the time knowing I'd be doing what I'm doing now on my other engine.

 

[xs650newb]

Ok. Looks like I'll split the cases.

As some people mentioned this also adds the benefit of looking for the little pieces of metal off of the master link and I can replace all of the seals.

Best,
Adam