New S2 Avant Nothelle N300 owner

[Tractor Dave]

The only thing I could think of is that the cam pulley has sheared it's keyway and slipped

Yes, the penny dropped a few minutes ago. I did suspect something wasn't right with the top pulley as I noticed some play there. I have a new one on the way from AT in Germany RXL getting it for me. Hopefully there is no valve damage as the cams still seem to be in time with the flywheel (somehow) and the non start is explained by the hall sender giving a signal at the wrong time.

[Tractor Dave]

Yes, it seems the cam sprocket has slipped a complete 180 from where it should be.
This means you still get the pin and the hall window lining up so the fuel pump runs.
But the timing is 180 out
This is a complete fluke of the worst kind

[John.]

I'm keeping everything crossed for you! You never mentioned it sounded compression-less when cranking so hopefully all is ok.

[Error404]

What are the chances of that?
Fingers crossed no bent valves for you Dave.

[Tractor Dave]

What are the chances of that?
Fingers crossed no bent valves for you Dave.

Is there an easy way to check valves? I don't really want to remove the head unless I have to.

[Error404]

Leak down test is the best way

[Tractor Dave]

Leak down test is the best way

Cheers Alex. I need to buy a compression gauge!

[newsh]

You need to leave everything on TDC and lined up, carefully swap the pulley, torque it to spec and tension the belt correctly.

Turn it over by hand and check timing marks again

Then do the compression test.
If it’s below spec then the head comes off.

You could also try a scope down the bores and look for marks on tops of pistons.

Personally I wouldn’t touch it till you’ve got the new sprocket on there.

[jogi730]

Oh dear. FIngers crossed it's nothing serious

[Tractor Dave]

You need to leave everything on TDC and lined up, carefully swap the pulley, torque it to spec and tension the belt correctly.

Turn it over by hand and check timing marks again

Then do the compression test.
If it’s below spec then the head comes off.

You could also try a scope down the bores and look for marks on tops of pistons.

Personally I wouldn’t touch it till you’ve got the new sprocket on there.

Thanks John. I borrowed a scope yesterday and all the piston tops look good. I'm not touching it until the sprocket arrives. I need to have a conversation with my engine builder as well. The top sprocket bolt wasn't correctly torqued

[Rikki Kitto]

Nightmare bud hope things aren't too bad, when you say conversation does it include a big stick

[fish]

Any progress here?

[Tractor Dave]

Any progress here?

Just waiting for the new top sprocket.

[newsh]

Just waiting for the new top sprocket.

When you rotate the cams 180 deg to the correct position I think you’ll have to release the caps and lift the cams to avoid valves hitting pistons. There’s a sequence to releasing and tightening the caps to avoid cracking them.

If you’ve not already got a bent valve or 2 it will be a miracle. Doing this will avoid bending any more.

[Tractor Dave]

Thanks John. My engine guy is coming over when the sprocket arrives.