Hi Buz......

Sorry to hear you lost the muffler. I've scattered a few around the weeds in my years too. It happens.

The muffler patterns are sorta standardized. The european engines and 'eastern' engines use different spacing.

In the 40-50 size range.... Webra, ST (as well as Jett ) use the same 38.5 mm bolt spacing. OS, TT, Tower, Irvine, ASP, Magnum (and other similar clones) use a 37mm bolt spacing.

A suggestion if you are replacing the muffler. Consider a Jett-Stream muffler. It works very well on the ST engines, and is a one-piece bolt-on design. It will not come apart. No adapter or modificiation... its provided with the correct bolt pattern for your engine, and suitable bolts. It will also increase the engine rpm quite a bit. The resulting performance gain will most likely put a big grin on your face Price wise, it may be a few $$ more than some other options, but its not much more, and its wise to consider all of the factors. More info and performance data is available on the web site

I hope this is helpful
Bob