Broke the engine?

Well, being as you have just rebuilt the engine, all of the rebuild things have been done, so I would think that you could replace the chain by just removing the valve cover and snaking the chain first down from the top and then flip the engine upside down and snake the chain from the sump opening back to the top. To get passed the front chain guide you may have to use coat hanger wire to pull it through.
 
I'd want to get the head off at the least. Valves have springs that are always trying to press them shut. I don't see how they could stay open after the chain is gone? It's possible something went wrong in the top end and the chain snapped as a result.
 
xs650newb said:
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
Click to expand...

All you need to do is remove the engine, and take off the head/cylinders. You can even leave the pistons inside the cylinders, if you just pull the wrist pins. I see no need to split the engine cases. Look carefully through the oil in your drain pan, and you may yet find the missing master link side plate.

It may have been a combination of camchain to tight as the engine expanded (even for 5 minutes), and master link pins not peened correctly. Are you confident that you peened the master link properly?
 
What is the likelihood of the valves not being bent? Excuse my ignorance, but isn't this an interference engine?

I recently replaced a chain on a different motorcycle, I opted for the continuous chain. I had to break it and rivet it back together, but it wasn't too big a deal with the proper tools. Mike's sells the tools for a reasonable price. I managed to borrow one. FWIW, Tsubakimoto is the OEM supplier.
 
Ok. I think retiredgentleman found the issue.

I put the master link clip on properly (I believe) but I did not peen the pins.

Well, that was a stupid mistake which is going to cost me a new headgasket, bottom gasket, and a lot of time.

When I have the top end off I'll look around for damage to the valves.


Along the lines of what MAarty said, when the cam chain broke the camshaft stopped spinning meaning the valves are now stationary. In this case, the exhaust valve on one side is open and the intake valve on the other side. Depending on how many revolutions the crank shaft (and pistons) made after the chain broke isn't it possible that a piston smacked into an open valve?

I didn't here any noise that would indicate that would happen but anything is possible I guess.
 
Agreed Marty. There sure is a very good chance that the valves got bent. With the head off, you certainly want to do a thorough inspection of valves/rocker arms etc. The top of the pistons may show contact damage.
 
Thanks retiredgentlman and Marty.

I had a look through the spark plug holes and saw no damage to the pistons but obviously when I have the head off I'll give it a thorough look through. How do I know if a valve is bent. If it won't slide freely through the guide? Or is it a much more dramatic look.

Adam
 
How do I know if a valve is bent.
Click to expand...

It won't close or seal all the way. What you could do is get the valves closed before you take it apart. (remove the cam) Do a compression check. No compression = bent valve
 
You don't have to split the cases to install another cam chain. The top end needs to be removed - cylinder head and barrels, check the condition of your chain guides and tensioner assembly as well. I want to know what process you used to set the chain tension on the recent rebuild, as well as the brand of chain installed + the method used to pein over the master link.?
 
jetmechmarty said:
It won't close or seal all the way. What you could do is get the valves closed before you take it apart. (remove the cam) Do a compression check. No compression = bent valve
Click to expand...

I don't think you can do a compression check without the intake valve opening to suck some air in to be compressed. You could, however, do a leak down test.
 
Hi hotdog,

To answer your questions:
1) I set the chain tension too tight initially and allowed the bike to idle for about 5 minutes before realizing my mistake. After realizing what I had done I set the tension by allowing for 1 mm of free play in the plung as the engine was running.

2) I forgot which brand of chain I ordered, but it is the one sold by 650central.com which is NOT endless. It comes with a mast link. It says on the master link '219, FTS' if that helps.

3) I did not peen the pins. That is the mistake I made.

Adam
 
Hi pamcopete.

About the leakdown test..I mentioned earlier on in the thread that the intake valve on the left side and the exhaust valve on the right side are open. I suppose this makes the leakdown test not do-able as well?

Also, without the chain on the camshaft what is keeping those valves open? I take it that the valves must indeed be bent.

Adam
 
If you pull the tappet covers you can check the rockers. If one moves more than just the lashed clearance the valve is bent. Basicly the valve face will be bent and not completely seating that will make the valve to rocker gap larger.
 
Thanks for your reply - just wanting to know how this happened.


xs650newb said:
Hi hotdog,

To answer your questions:
1) I set the chain tension too tight initially and allowed the bike to idle for about 5 minutes before realizing my mistake. After realizing what I had done I set the tension by allowing for 1 mm of free play in the plung as the engine was running.

2) I forgot which brand of chain I ordered, but it is the one sold by 650central.com which is NOT endless. It comes with a mast link. It says on the master link '219, FTS' if that helps.

3) I did not peen the pins. That is the mistake I made.

Adam
Click to expand...
 
Ok. Everything that is being said makes sense.

I most likely will not get around to getting the engine apart and on my work bench till later in the week.

Stay tuned.

Adam
 
jetmechmarty said:
The position of the camshaft is keeping the valves open. They should close if you were to remove it.
Click to expand...

I don't think it's that simple, but we can't know without looking. To my mind, with no chain to hold the cam still the valve springs should have immediately driven the cam round to where they could close. Even when the chain IS in place, stopping at TDC with the plugs out is tricky because the valve springs have enough strength to turn not just the cam but also the chain, the crank, and slide the pistons all so they can get themselves closed. Two open valves is something over 200 pounds of force pressing on the cam isn't it?
 
That would be possibly true if there was only one lobe and one spring. But there are 4 lobes and springs all working with/against each other under tremendous force.

Toss in a couple of bent valves into the mix and a jammed broken cam chain and it's not a surprise that the cam isn't moving.

Lot of talk - take the engine apart :) There are no shortcuts when you break a cam chain.
 

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