Cam Caps or Cam Stops

So here is my heart break. A broken but semi functional Cam stop/Cam cap/journal cap??? What is the correct name and how do I replace this piece. Can I just unbolt it, the reassembly directions say to be extremely careful when tightening, does this hold true of the disassembly process? Or do the other caps make this and easy process.
Is there a crush bearing invovled?
What exactly is Plastiguage and how do I place it? When I've figured out the specs of the caps then what do I do?
Is this something that Chacal canhelp me with??

What do I do about the missing piece, I don't see it in the head, do I need to pull the pan?
thankyou
DRat
And thankyou PO :cry:

 

I'll give you the answers I know, and other more informed people will be along shortly to fill in the gaps.

1) Plastiguage is a thin filament of plastic that you put between the cam and the bearing for instance, torque it down to spec, disassemble and measure how far the Plastiguage has spread and it tells you the clearance between the cam and the bearing so you can see if they are in spec. Its Available at any good auto parts store.

2) Since the piece is not in the top end floating around, I would say that a previous owner broke the piece and reinstalled it broken. I can't think of a way that a piece of that size could get from the valve train down into the oil pan (but I could be entirely wrong)

So all in all I'm not a whole lot of help :S

 

That piece needs replacing before your have a catastrophe of unimaginable proportions occur..........

And no, there are no thrust washers or crush bearings involved in the valvetrain. The machined saddle in the head and those cam caps ARE the bearing surfaces.

Let me know which one it is (intake or exhaust, and which cap, left-to-right) and I may have some used ones........HOWEVER, I have no way of knowing whether these caps were "all the same" for various engines or whether they were "sized" somehow by the factory to meet individual engine tolerances (Yamaha never published part numbers for the caps, so it's really hard to tell what they were doing).

 

I can't quite tell from the pic is that a "real" one or a "dummy?" Both inner cam caps don't have bearings in them, only one side. The other side acts as a lateral stop and a support for the valve cover, nothing else. Not sure which is which on a 750 or if they're exactly the same as the 550 so I can't be too specific. You might be lucky. If it's the dummy you don't need plastigage, just the part.

The missing bit doesn't look all that big, it could have traveled down the camchain "well" and made it into the sump. It's small enough if it IS down there, it probably won't hurt anything. I'd drain the oil and peek thru the hole with a flashlight tho. Then dropping the sump is up to you. I would NOT flip the bike on its back for that, the bit could fall UP into the motor.

 

Big, Chacal, and ACE I appreciate the responses.
It is the cap on the riders right of the exhaust cam sproket. I belive there are numbers stamped into it, I'll get those soon and post.

Big, Do I just need to pull the cap off to tell if its the dummy or can I tell by looking at both of them in the cold hard light of day. If its a dummy or not what is the correct removal process. Do all caps have to come off so that the reassembly follows the factory manual directions. Or are we good to just pull the one? Let me know and I'll pull it and take photos....

As for the piece in the pan.... The engine is comming out, I need a new frame, I probably do it then.

 

I believe this photo clearly shows that this cap is the "dummy cap" Big talked about. There is a 1/4 inch gap between the cap and the cam. The cap on the other side of the sprocket looks to be a percise machined piece where tolerances are an issue. Does anyone think I'm making a bad assumption. I can't see any reason why this wouldn't be a quick swap with any matching piece regardless of tolerance.

 

Here is a photo of the non-dummy side, I hope these photos clearly indicate the difference between the two caps

 

Each bearing cap is unique.

When the head is manufactured the cam caps are bolted in place and then the whole head is line bored for the cam. That's why they're not interchangeable and have to go on in the original direction. That's what those half moons are on the head that are so prone to oil leaking - clearance for the boring bar.

In theory when one breaks the head is junk.

If there isn't a bearing under that cap (I learn something every day!) you're in luck. Any cap should do. Or even have that one welded up and re-make the hole.

Oh, don't look for 1/4" plastigauge. They don't make it that big :wink:

 

That is the dummy side. You just need to find one from a donor bike. I have a few but they are either from a seca 550 or from a turbo 650 engine. If you can't find one locally email me or send PM and I can send one out.
Sean

 

You have options:

Since that piece is used to hold-down the Cam Cover ... you should replace it.
A donor piece from a scrapped engine will do the trick.

Although the Piece is a "Dummy" Piece ... its still FUNCTIONAL.
One side has and indicator on it for Timing.
The other side has a Flat machined surface that acts as a THRUST Surface.
The Flat side keeps the Cam from moving Left and Right in the Journals.

The Piece can be welded.

http://durafix.com/

 

You are a lucky individual. That is indeed the "dummy" cap; yes it does have a function but it is not a precision tolerance like the bearing side.

You just need one from a donor bike; I would try to get one from a 750 just to be sure everything lines up OK. I'm in the same boat as Sean, I could send you one but it would be from a 550 and I don't know if they're exactly the same.