Help, I think I mixed up my cam caps!

Hi all

I’m absolutely furious with myself. Rebuilding my 1990 XJ900F engine and have been careful throughout the whole process to keep my cam caps in the order I removed them. Literally just after I fitted the head back on, I somehow managed to knock some of the cam caps out of sync on my work bench.

A few I know where they go, but some I may have mixed up. There are odd markings on the cam caps. Do these give any clue as to what order they go in?

After all my hard and costly work, and the care I’ve taken, for this to happen now is enough to break me!

Shaun

 

Typically, the actual BEARING cam caps have an I or an E stamped on them (intake of exhaust), and some may even have a position number (1, 2, 3,etc.) on them. Some may also have a pointing arrow cast into them, which indicates either:

a) pointing towards the cam chain tunnel, or
b) pointing towards the left side of the motor.

EDIT: correcting the above to state that the arrows on the BEARING caps always point toward the right side of the engine (the clutch pack side of the engien).

Non-bearing caps can be used in either the intake of exhaust position for their designated spot.

For the actual bearing caps, you can actually use any one in any position (as long as they are the proper type, i.e. 2 holes vs. 4 holes, etc.) but it would be recommended that they be checked for proper oil clearance (plastigage mesurement).[/u]

 

I just happened to have the cover off mine, so I took a couple shots for you and did my best to try and identify any markings.

Chart below shows the marks I could sort-of identify on each. IA-IF are the intake side, from clutch (left) side to throttle (right) side. EA-EF are the exhaust side. Cam chain is down the center.

Cast means it looks like the numbers were raised and look like they were cast into the part.
Stamp means it looks like somebody stamped it with a character punch.
< or > next to the letter identifiers indicate the direction that the cast arrows are pointing. All point to the right except the ones to the left of the cam chain.
The <-> in ID were two tiny lines that looked like they had arrows on the ends, offset from each other.
The triangles looked like some sort of triangle symbol maybe with something in the middle, but really small and hard to make out.
EA and IA are shaped the same.
EF and IF are shaped the same.
EB, IB, EE, and IE are all shaped the same.
EX, IC, ED and ID are all shaped the same.
EC and IC were the only two I couldn't find anything that distinguished them from one another. Maybe there was something different about the triangles, but I couldn't see it.

No guarantee I got all these correct. My eyes aren't as good as they used to be, and I had a hard time getting a good camera angle that was still in focus.

Also, whether somebody was in mine before me and mixed them up, I can't say. I don't have any reason to believe they've been pulled, but the PO did some kinda screwy things so you never know.

 

@chacal interesting that you say the point to the left side. Almost all of mine point to the right except on the cam chain tunnel which both sides point away from the chain. Hmm.

 

Oh, just realized you said 1990...mine is an '83. Not sure what difference that makes. Oh well, at least it's documented if I ever need it myself.

 

I may have that wrong, or, it may be that different engines have them marked/oriented differently (doubtful, but that's my story and I'm stickin' to it.........).

And IF I recall correctly, all of the caps that have the central threaded boss (for receiving a valvecover bolts) are the NON-bearing caps....their inner radius will have a rough-cast finish to them, whereas true BEARING caps have a smooth, machined finish. THIS STATEMENT MAY ALSO BE INCORRECT, and it's the "rough vs. machined" inner radius which is the determinative factor.

Obviously, NON-bearing caps can be safely swapped, and even the bearing caps can be swapped but you should really verify clearances.....although, if the oil clearances are way out-of-spec, there's not much you can do about it, besides trying to buy other used caps and hope you luck out. Yamaha (with a few exceptions, which always struck me as odd) never sold replacement caps, and advised that the entire complete head be replaced (!!) if the cam caps had too large a clearance or were damaged.

 

Looking at my pics, the ones closest to the cam chain are the only ones that don't appear to have a machined bearing surface. So, like you say, they shouldn't matter where they go, which is probably why they are somewhat ambiguous with markings. The rest all have enough markings on them to identify their original positions...at least on my '83...that was probably assembled on a Tuesday...as opposed to Thursday bikes which pointed the other way...

@ShaunR, good luck.

 

Just to back up Chacal I do recall the orientation of the caps were machined marks always lined up with machined marks as these were line bored while the cam cover bolts always threaded into non-machined bridge caps. The caps on my XJ750 SECA were also numbered to their position, look at the arrows on the bridge caps and use these to match the others up. I had mine out to drill, tap and helicoil the threads and do remember the orientation was important because of the bolt offsets. Markings I were intake, E exhaust number was cylinder position arrow was point toward half-moon... according to the photos I took of mine before I started the work however I'm not the original owner so...

 

Okay, looking through various Yamaha shop manuals and aftermarket Haynes manuals, it seems as though the ARROWS always point towards the right (brake hand lever) side of the bike.

However, the Haynes 900 manual (which is the best manual out there) says that the caps mounted adjacent to the camchain sprockets are not bearing caps, and that the directional arrows cast into these non-bearing caps must face AWAY from the sprockets. ....which is exactly what is shown in the images posted above by co.dirtbiker.

So in the case of the 900 engines, all of the arrows point in one direction (to the right) exceptfor the caps just to the LEFT of the cam chain tunnel / sprockets, which will have have their arrows pointed to the left side of the bikes, and in opposition to every other cam cap with an arrow cast into them. This can be seen in the "upper" picture, and is most easily noticed on the exhaust camshaft side of the image (the camshaft on the right-most side of that image).

It's also odd that Yamaha released a replacement camshaft cap for the XJ550 engines (also fitting the TX500 and XS500 engines), it's a fully-machined cap with the bolt hole for the valvecover bolt, but that cap is not in any parts list, and it defies explanation how a machined cap could be offered as a service part since the machined caps and the bearing saddles in the heads were machined "all at once" during production and thus cap diameters can and do vary. Never figured it out.........maybe there was some hitherto-unknown flaw in this one cap during early production that Yamaha tried to remedy by releasing just that one cap for warranty service (rather than replacing entire cylinder heads, caps and all) and eventually the leftover inventory of these caps escaped the limited confines of the internal Yamaha-dealers-only parts network and got out "into the wild" (they're all over eBay, and have been for some time).

 

That jives with what I found on my 750 so I can say its right then.

 

This is really helpful. Thank you so much.

 

Wow! A BIG thank you to everyone who posted answers to my conundrum! It’s only a few caps that got knocked out of place on the bench, so I’ll examine them carefully. Some have marks as clear as daylight, others look like they’ve been stamped by someone half asleep, almost like scratch marks.

The engine is now nearly complete, and resplendent in a gun metal grey colour with sort of dark plum coloured bespoke CNC engine covers to echo the style of my old VMAX 1700. Wire wheel conversion is complete, mudguards, custom side panels and XJR fuel tank gone for painting. Just about to take the frame for powder coating and then the fun of the build can start!

It will still be an XJ900, but not as you know it!!

Thanks again.

Shaun