Exhausting all possibilties

[b490]

Rebuilt my XR500 engine recently
Fired up 3rd kick ... ran fine for a couple of minutes ....then she not rev much past idle .
Hmmmm?.....
 After a few hours of  checking  / cursing / headscratching ......
Inner wall of left header pipe let go .... one would think a collapsed/ blocked  muffler would be more  likely to be  the  usual suspect of an exhaust restriction
 



Bike running fine now
 Regards ,
               Steve

[Mike52]

Now that is different.
How did you find it 

[Curly3]

That looks like a machine operators prank to me.
That shouldn't happen, unless it was deliberate.
I've seen deliberate sabotage in other fields, but that is a goodun.

[b490]

Re Checked all the basics  first ; valve  timing & adj , fuel , coil ,cdi , ignition advance , looked for muffler restriction .Removed  muffler  & ran bike ...still no good ; didn't even suspect header pipe at this stage  ....not much there to go wrong .....so I thought.
(this was a spare header pipe that I  had not used previously) ....jeez it should of set the bells off sooner 
Leak down test showed nothing obvious , so out with the motor me thinks .
Removed header pipe ......thinking ..... nah .... but I'll take a good look anyway ; grab torch and look into headers .
Noticed something odd inside  bend area of L/h pipe ;  very difficult to notice at first as it was at pipe bend area    ....... was nothing odd on outside  to give any clues.

Regards ,
               Steve

[matcho mick]

more common than you would think!,came across that problem occasionally, working in honda shop with the two pipe hondas, CB250RS roadies did it too,always down on the bend as yours did,

[b490]

 I have not seen  or heard of this problem  before Mick .
Had  Me & a mate (both mechanics ) buggered for a while 
 We did all the checks on Monday ..come up with nothing .
We have both owned a few twin port exh Honda's over the years .....never seen it before 
I looked ...... & thought a lot more Tuesday ..... over & over ...looking  again ....glad I found it .......finally.

Regards ,
               Steve