Exploding Exhaust Gasket

[vacationer]

So ever since I bought my Zuma (88-01), it’s been pretty loud. I was told this was because the CVT cover was cut, which makes sense to me. But recently, after I removed and painted my exhaust and repacked the silencer, it’s gotten gradually louder. This week, I noticed the exhaust was attached by almost nothing and fixing to just fall out. Apparently one of the bolts holding it the cylinder had snapped as a result of the fact that the large bolt on the top side of the exhaust on the outside had disappeared at some point.

Yesterday, I put some new bolts on and replaced the former paper gasket with a plastic one about half a cm thick that had a rubber o-ring seated inside a groove on one side. I put some high temp gasket maker on as well since the gasket wasn’t a perfect fit. Today, when I started up the engine, it was quieter than I’d ever heard it, but after about a minute of riding, part of the new gasket broke and flew off.

What did I do wrong?

[aeroxbud]

I'm not sure what gasket you used but there are usually two types of gasket. A round "O" shaped one. Which usually sits in a recess in the flange of the exhaust. www.pedparts.co.uk/product/646/yamaha-aerox-exhaust-gasket-leo-vince?ga4List=
Or one shaped like a football which locates over the studs. www.pedparts.co.uk/product/827/scooter-moped-exhaust-gasket?ga4List=
They don't sound like what you fitted.

[oldgeek]

Sounds like you used a carb intake isolator instead of an exhaust gasket. Plastic will not take the heat the exhaust produces.

[vacationer]

oldgeek Okay that’s definitely what happened. I guess I just saw the shape of it and assumed.

I found in my stuff a used gasket like the one in the first link you posted, aeroxbud. Think I can use it again?

I’d use the paper one but I think the reason the exhaust was coming off before was that, with a paper gasket, the pipe doesn’t align both with the bottom bolts and with the one on the outside - at least not at the same time.

[oldgeek]

The old donut style should work if there is a recess for it to sit in. Flat exhaust gaskets are usually made of some type of heat resistant fiber and may even have a metal ring. I do not think a paper gasket will last very long at all, if it is actually paper it is likely for that carb intake spacer you had. It can be very difficult to get a pipe to fit, dont force it!
These are also good gaskets.
www.ebay.com/itm/233785048335?hash=item366eacbd0f:g:QyoAAOSwzcNcNLzn

If you dont need the exhaust studs
www.ebay.com/itm/335020631706?epid=899075065&hash=item4e00c9269a:g:A-EAAOSwBVdcRfvn

[vacationer]

Okay duh. Not sure why I thought a paper gasket would last. I ended up reusing the ring gasket and it’s worked like a charm so far. I was worried it wouldn’t be wide enough, and it still might not be so I’ll have to keep an eye on things.