I think I've done something wrong!

[McCabe-Thiele (Ted)]

That's bad luck Sean - I've generally  ensured that the dowels are on the fixed surface first so they can't drop out. It has meant I have had to replace a few as they chewed up a tad on extraction.

As has been said any unaccounted for big lumps should drop down into the sump - goes without saying to change the oil filter. Have you fitted a magnetic dump plug might be worth it as belt & braces.

[Skoti]

I can see how the bolt came out if you didn't put locktite on it but I can't fathom out how the dowel got involved in the failure 🤔🤔🤔

Julie, maybe Loctite is something you recommend, but there's no mention of that in the official Honda CB400F shop manual over in Aladdin's cave.
I built a fair few of those Honda engines during my years in the trade and never had fully tightened cam sprocket bolts come loose.

Bit of bad luck for Sean tho, hope he gets it sorted out.

[Nurse Julie]

I can see how the bolt came out if you didn't put locktite on it but I can't fathom out how the dowel got involved in the failure 🤔🤔🤔

Julie, maybe Loctite is something you recommend, but there's no mention of that in the official Honda CB400F shop manual over in Aladdin's cave.
I built a fair few of those Honda engines during my years in the trade and never had fully tightened cam sprocket bolts come loose.

Bit of bad luck for Sean tho, hope he gets it sorted out.

Indeed you are correct Scoti but if locktite or similar had been applied, it wouldn't have come undone. It's just belt and braces really. It's like the cap / plate that holds the cam chain guide in place at the top, I would advise using locktite on those 2 bolts as well.

[Oddjob]

I've never used Loctite on those bolts, so long as they are torqued up they should be fine.

As for the dowel, I tend to locate any dowels in the head rather than in the rocker cover, they shouldn't fall out if they are in the head, as gravity keeps them in place.

TBH I suspect the cam sprocket bolt was never tightened rather than came loose, you tend to fit one but not tighten it, just in case it locks the sprocket out of alignment for the other bolt,  spin the engine until the other comes up so you can fit that and then forget you haven't torqued up the first one and move onto something else, anything can cause this, someone speaks to you, a phone call, just something that breaks your concentration, easily done.

[ST1100]

TBH I suspect the cam sprocket bolt was never tightened rather than came loose, you tend to fit one but not tighten it, just in case it locks the sprocket out of alignment for the other bolt,  spin the engine until the other comes up so you can fit that and then forget you haven't torqued up the first one and move onto something else, anything can cause this, someone speaks to you, a phone call, just something that breaks your concentration, easily done.

Which is why I prefer to work on my own...
And I adapted the Japanese way: Edding 8750 industrial paint marker...

[McCabe-Thiele (Ted)]

So that's why I have yellow dots on my engine bolts to remind me they have been torqued up!

[Oddjob]

Yellow paint was used by Honda on the production line for that very reason Ted, it also showed if the owner tampered with the bolts in case of warranty claims.

[SeanFD]

Using a magnet, I was able to fish out a couple of additional bits.

Then I turned the motor over slowly - yes Ted, the plugs were out - and all seemed fine.

So now it will have to sit for a while until I get back to Belfast, when amongst the other things, I'll drop the sump, check the strainer and change the filter.

Until then ...

[McCabe-Thiele (Ted)]

That's bad luck Sean - I've generally  ensured that the dowels are on the fixed surface first so they can't drop out. It has meant I have had to replace a few as they chewed up a tad on extraction.

As has been said any unaccounted for big lumps should drop down into the sump - goes without saying to change the oil filter. Have you fitted a magnetic sump plug might be worth it as belt & braces.