Forgive my lack of knowledge here, but I was able to purchase a couple of these little FL250s that were in pieces. Have the motor (( Internal Combustion Engine ? )) assembled, and about to mount the exhaust pipe to the manifold. My question is this: On the manifold itself there is a ring, I'm guessing for the gasket that I've seen in the parts diagram, but on that diagram, it also shows an exhaust ring? Just need to know if I need that and how this all goes together. The ring is #7 in the diagram.

#7 is a metal ring that goes on the flange that bolts to the cylinder. Your exhaust pipe is held onto this flange with the two springs. The other o-ring is a seal as well. Good luck trying to find the metal ring. I broke mine on my fl350 and have not been able to find a replacement. I now use exhaust cement made by kleen-flo or you could do what others do here and use red silicone.

7 the steel ring goes in the groove of the exhaust manifold. 5 is a fiber ring to seal the manifold and the exhaust pipe joint. This is a poor design as the fiber ring doe not hold up and usually is gone the next time you take the pipe off.

I would not waste my money buying one. Hoser uses red high temp silicone to seal it up. He has write up here. If you do it let the silicone dry for at least 24 hours before you touch it. Make sure all parts are clean.

Personally I just run the expansion ring.

Now the 250 is known for plugging up the exhaust. You may want to make sure your exhaust is clear before you seal it.

It's like a auto exhaust and you have to worry about an exhaust leak.

Thanks for the info. I have located the metal ring, and will probably just use red silicone instead of that seal. One question about that though, is where should I bead the silicone? You say wait 24 hours to touch it... do you mean seal the pipe, and wait 24 hours till I try to run it?

Hoser original article. http://pilotodyssey.com/Silconesealer.htm

When I had/started off with the 2 fiddys,I noticed the build up of years of carbon,gunk lining the pipes.
After I did a service on the carbs,Ody was sluggish before, better after service,but nothing to go yeehar!
A local mechanic wanted an arm+leg to cut,clean out and patch up the muffler.
So I decided to bake the pipe in a half 44gal drum of nice hot coals.
After a bit,smoke was coming out the ends for yonks,then turned it over and finished heating the other side.
When no more smoke,let cool down,then with soft pine type wood,bang it gently,but firmly and you'll hear the now dry baked gunk just break up in there.
Then turn it all around and shake it to remove the bits.I used my garden petrol blower in one end,while twirling the pipes to work with gravity.
Eventually got it all out,installed it and noticed the diff straight away.
Easy/quick start up,smoother idle,great power delivery thru the whole range...I was yeeharing!

PS: Don't let gravity get ya down!

The twisting and turning with pipe and blower,will also improve your dance moves like P Garret.
Here's some vid to practice by,good excercise too.He obviously had the Odys too

Gives and error stating not found. Tried to check this out earlier.

hoser can you fix this link?

At this point I would recommend you run it with just the spings and expansion ring. Once you know it runs well you can then seal with high temp red silicone.

To answer your question. I would put a fat head around the outside of the exhaust manifold, close to the outside edge. Then I would out a fat bead about a inch just inside the pipe. Make sure things are good an clean. Wipe the parts down with carb cleaner first. Install the pipe and springs. Bolt it down and walk away for at least 24 hours. It will never hold if you start it before it curs.