Hello all.  i have done an awful amount of reading and now have a question.  I have a 175B and since I have had it there has been an exhaust leak where the end piece (about 18") goes into the main exhaust pipe.  The diagrams shows 2 o rings sealing this joint however this does not seal mine I still have some smoke coming out of the joint.  how do you guys seal this connection or can it be sealed?

Have you completely and thoroughly cleaned the muffler/spark arrestor? (Usually needs to be done by burning out carbon or with a heavy duty chemical wash...  some have had it hot-tanked at a radiator shop)

(If o-rings are in decent shape, I don't remember leaks at that joint being a problem...  which is why I'm asking if perhaps muffler is clogged?)

A little silicone seal on the o-rings might help but it might be hard to get the muffler out again if you use too much?

thank you Mark, i did put the exhaust on a fire and kept it on and going until it stopped smoking which it finally did. When I install the muffler into the exhaust pipe the o-rings either disappear or are missing a small section the next time i take it apart. And of course it is leaking at that connection.

Sounds like you need to check the opening where muffler pipe fits into for burrs or other damage.  Maybe pipe opening is rusted out or something?

(Not sure how o-rings would "disappear" unless there was obvious damage?  I've never had that problem or heard of it.)

Genuine Yamaha O rings?

yes oem o-rings. i will check for burs or sharp edges. the last one that i checked was missing about 1/8th of it so i think they are being torn and blowing out or coming out some how.

I've never tried this, but I wonder if it would help to put a few wraps of Teflon tape around the new o-ring.

Ok, so now you know what kind of backyard mechanic I am.