Removing Y pipe to change gaskets

[hoverhead47]

Ever since I installed the replacement exhaust system (more than 20 year ago) I've had a slight leak that I've never quite managed to locate. Since I've started riding again that leak has become a little more pronounced. Also it might the source (on overrun) of the crackle and pop that has developed since the carb re-kit. So my question is now that I've located the laek at the tops of the Y pipe, is it possible to remove the Y pipe with the engine in situ or do I have to remove the engine in order to fit new exhaust gaskets?

[QBS]

Yes.  No.

[cvincer]

....... & when you put it back together, I'd strongly suggest you use something like  Loctite 596  Hi-temp silicon sealer.

[hoverhead47]

Started the removal process yesterday, did a bit more today.
Found that I have bought a gasket in anticipation that I won't be able to use as the after market system pipe clamps directly onto the Y pipe without the gasket.
The problem I have now it that the copper gaskets in the flex coupling are worn out.  One just fell in two pieces when I got the coupling undone and the other has been severely eroded by the gasses. The other part is the the ring stoppers are eroded too. I've been able to find the ring stoppers and the gaskets but so far I haven't found any exhaust pipes as I expect they are quite eroded where the gaskets sit also. 

[Re-Vision]

I can find you a Y pipe if that is what is needed.      BDC

[hoverhead47]

The Y pipe at the moment hasn't let go of the collector but appears t be in OK shape. What I'm expecting is that the other side of the flexable coupling will be erroded as much as the stopper rings and the gaskets.  I've got some gaskets on order and I think I might've found some stopper rings.  The stub pipes are my main concern at the moment.

[QBS]

Did the connections in your system exhaust system leak badly for a long time before you began your current repair project?

[hoverhead47]

Yes, pretty much from the time I installed the replacement exhaust when I repaired the bike after a crash (1990?) it seemed to leak from behind the rear cylinder. I installed new gaskets and and stopper rings but couldn't isolate which joint it was coming from. I has only been since I've got it buck up and running and doing some all day(club) runs that the leak has become more noticeable, I have repeatedly gone looking for it.  I even tried a garden hose to listen for it. 
I had kitted the carbies as part of the return to running processes and that introduced the "Stumble" so I've been chasing that.  A crackle came into the picture when I returned a couple of  the original jets to the carbs to go back to the old settings. I had bought some exhaust gaskets as part of the return to running but never installed them as I didn't manage to get all the types needed and thought I'd see how it goes.  Plus the dread of having to pull it apart maybe more than once was a disincentive.

Looking for some of the causes for the pop and crackle caused me to finally bite the bullet and remove the exhaust and the Y pipe literally falling off the stub pipes and the two piece gasket is what I found.

[The Prophet of Doom]

A bit late now, but couldn't you use a shop vac on blow taped to rear, and then paint the pipes with a dishwashing liquid solution.  Bubbles = leak ?

[hoverhead47]

Good idea and could be used to double check when reassembled. After all I had new gaskets when installed system and couldn't logically reason where the leak was.  The after market system though doesn't use the large gasket from the Y pipe to the collector, it has a slip on clamped joint without gasket.