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[TheBoy]

Waterpump sounds fine - if it had lost rollers out of bearings, it'd be like a cock in a sock.


The extra strip down isn't wasted effort, as I think we all know the heads have to come off anyway.


With the timing not more or less in the right place, can you spin the crank through 360 degrees now - you'll get compression, but not a hard lock (hopefully)

[Dave G]

Just been back out to check that.

Turned the crankshaft through 2 revolutions. There was lurching as compression came and went, but no clicking, clanking or knocks that I could hear or feel.

[YZ250]

.......
To get the plugs out for a manual turnover is going to mean a lot more disassembly, plenum, piping etc. but if it has to be done…
.......

If you want to remove the spark plugs, and bearing
in mind I'm working from memory here, but to remove the coil packs covering the spark plugs, remove the 2 bolts holding it on, find 2 more suitable bolts that fit the top thread in the coil pack and pull it up. When it has a bit of freedom, undo the multi-plug connection under the scuttle area. The 1,3,5 bank is easy but the 2,4,6 bank is slightly more awkward as some pillock designed it so that the cable tray is in the way. Once the cable tray is removed, hold the cables clear with a bungee, but make sure the cables aren't stressed. Remove anything else in the way that I've overlooked.    If you get that far, I expect you to report back that plug 6 is an arse to access. 

[cam.in.head]

as a basic check seeing as it seems to turn fine by hand would it be worth pulling the fuel relay and unplugging the coils and going for a starter motor spin over ?  this would show (by sound) if there was a good equal  basic compression rather than a fast spot . cant see how there would be no damage but if it turns fine by hand then trying shouldnt cause any extra damage  !

[YZ250]

as a basic check seeing as it seems to turn fine by hand would it be worth pulling the fuel relay and unplugging the coils and going for a starter motor spin over ?  this would show (by sound) if there was a good equal  basic compression rather than a fast spot . cant see how there would be no damage but if it turns fine by hand then trying shouldnt cause any extra damage  !

A compression test would be worthwhile as well. 

[Raeturbo]

Indeed although a leak down test would be more revealing

[YZ250]

Indeed although a leak down test would be more revealing

Most definitely.   

[Nick W]

Indeed although a leak down test would be more revealing

Yes, leak down testing allows for accurate, detailed diagnosis, whereas compression testing is for more basic, quicker, what approach should we be taking? thinking

[JamesV6CDX]

How does the PAS pump turn, by hand? It's an incredibly long shot, and I think they will be too big, but I am wondering if it's the internal vanes from the PAS pump. Not that I can see how they could / would escape.

I also wonder if they have come from the water pump. I'll see if I've got one I can take apart and have a look inside.

I can confirm that they are definitely not from: Camshafts, Aux belt tensioner/idler, or any of the cambelt tensioner wheels.

I suspect that one of these has got in between the belt and bottom sprocket and caused it to jump teeth.

The bad news: It's heads have to come off, for a repair (It will have bent valves)
The good news: unlikely to be piston / rod damage, knowing for sure the failure was at idle speed. As I said, I drove mine to Spain after a cambelt failure, and never touched bottom end.

As said already.... summer is coming, and I am now semi retired 

Here is the link from my repair back last summer, before the Spain road trip https://www.omegaowners.com/forum/index.php?topic=151019.0

[JamesV6CDX]

Also, I don't think they are any engine internals. They would be unlikely to exit / penetrate the block or sump at idle speed!

But, it is by far preferable to find the source of them, because if something is duff, and there are more of these pins left in it, another one could drop down and cause the same thing 

I think it's unlikely in your case, but I did once visit a chap who had a cambelt 3 teeth out, about the same as yours. He asked me to take a shit or bust punt, time it back up properly and turn the key.

I spent an hour muttering about how it was a waste of time, wouldn't work and we should just strip it down - and,  it ran bloody lovely.  Can't say it didn't harm valves/seating, but not enough to cause a misfire, and compression was "in the green" (about 170 PSI). He drove it for years afterwards.

What you want to do is get that timing mark in the 4pm position and leave it there. The one on the crank, the small toothed pulley - not the bigger one.  (This is the position where all of the pistons are safe from the valves, partially down the cylinders)

And then, using a TX50 socket, gently rotate each cam clockwise, and report back as to whether any of them encounter any resistance.

If they don't, I would then set all of the cams into the locked positions (marks 1,2,3,4 lined up with the backplate), set the crank to TDC, and then see if it'll time up properly and spin over freely by hand.

If it does, I'd take a chance and compression test it.

If it doesn't, or you meet resistance by hand, then it's got to come apart.

I'm pretty sure it's coming apart anyway, but.... that's the approach to take.

[JamesV6CDX]

Happy to come up and spend a day in the not too distant future to work with you and check it all out.

[Dave G]

Hello, thanks all for the posts last night...
Didn't want to post back until I'd done some more work.

Disassembly progressing - steadily.
Cams 1-2 were a tiny bit out so corrected that. I thought about trying to turn on the starter, but until I know what those pins are I don't want any more of them flying around.
Plenum now off, fuel lines disconnected, pump fuse removed (in case).

Followed James' instructions re: 4 o'clock positioning. No resistance felt, but still have three plugs to remove before trying plugless.

First bank, plug wells nice and clean. Cam cover this side not off yet, the circled bolts I could undo with my fingers, which I thought was odd.

Not checked the PAS pump yet - I'll do that before I undo more bits.
It's starting to get a bit scary now, with all the pieces I've taken off.

Thanks James for your offer of help - It's looking more and more likely that I'll need it !!
Here's the pix...

[YZ250]

Hold tight a bit Dave. I thought that you were just going to remove the belt, turn the crank to 4 o’clock and then turn each individual cam to see how they turned.

[Dave G]

Ah yes, you’re right. Crank is at 4 at the moment so that test won’t take long.
I’ll do that before removing anything else.

(When the hailstones give me a break.)

[Dave G]

Turning the cams needs a bit of effort - then they seem to lurch forwards in the direction I’m turning them (clockwise). No clanking or metallic noises.

First, both PAS pump and A/C compressor turn freely with no wobbles or noise.