How Bad Is This?

[TheLastJoker]

Hey guys, I'm working on my first rebuild of anything more complicated than a toaster and things have been going pretty smoothly so far.  On one side of the garage I have a pile of parts that have a 37% chance of finding their way back to the same general area of the bike and on the other side I have a bike frame with the engine and front wheel still on.  In preparation for removing the engine, I tried to take off the wedge shaped cover on top of the valve cover.  One of the screws was blocked by the frame but I was able to take a peek inside and see this.  On one side, there is this hole that does not appear to have been factory cut.  The engine ran before disassembly, though it seemed to have quite a bit of top end clatter... not sure how much is typical of these bikes.  Anyway, I was just planning on repainting the engine and kicking it back in, but would you guys recommend a more thorough tear down?  The bike had 27K miles on it.

BTW, if this question is in the wrong part of the forum, please let me know. Thanks!

[shinyribs]

That doesn't look very good actually.  I'm not sure exactly how close to the valve cover your timing chain is looking at that pic. Is it touching? If it were me Id definitely want to find that piece of cover before I ran the engine.

Maybe the chain tensioner is bad or out of adjustment and let the chain jump up and smack the cover???

[TheLastJoker]

Well I just kicked the engine over several times and the chain doesn't appear to get close to this cover.  There's a good 1/8" distance between the chain pins and the edge of this hole.  Do these engines normally have some rattle to them or are they pretty quiet running?  The metal may have already been ground up and flushed out in a previous oil change.

[TOOLS1]

These engines will sound like a can full of rocks being shaken; when the carbs are out of sync. If the chain is not touching the cover it might be OK, but I would do a more through inspection.
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[TheLastJoker]

That's actually some really encouraging information as I believe the carbs were out of sync.  I had good power and acceleration but it would stall out below around 10 mph without careful throttle/ choke management.  I'll remove the oil pan/ pump and valve cover and if I don't find evidence of rogue metal pieces I'll close the investigation and call it good.  Thanks for the feedback!

[sgtslag]

Make sure you adjust the chain tension!  Check the FSM (Factory Service Manual), downloadable from the Home Page.  There are two nuts, front and rear of cylinder block, which allow the auto-tensioner to function.  Cheers!

[TOOLS1]

That's a SOHC, it only has one adjuster on the rear of the cylinder.
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[Lucky 1]

There is nothing wrong with it at all.
That is how it was cast.
The casting just did not have a nice edge on it.

I thought the same thing but then found out they all look like that.

You need to tell us what year it is also.
On the SOHC the valve cover is different on the 77-78 models.
It looks  like the early model.

[TheLastJoker]

Lucky 1 wrote

You need to tell us what year it is also.
On the SOHC the valve cover is different on the 77-78 models.
It looks  like the early model.

Sorry for leaving this info out.  It's a '78 750F.  

sgtslag wrote

Make sure you adjust the chain tension!  Check the FSM (Factory Service Manual), downloadable from the Home Page.

Thanks for the tip! This was one of the first adjustments I did to my bike when I got it home, however I think it may be possible for the adjustment rod to be seized in the housing preventing it from moving at all.  I will be going over that part again for sure.