I bought a new (to me) 1995 SA50PS
It looks bone - stock.
Had 400 miles on it.
Am starting to do the "upgrade path"
Weighed the muffler before & after drain cleaner
<got about 1/2 lb out of it> ;
also bored out the exaust mounting flange restriction.
The flange hole looked like 1/4 inch diameter to start.
Drilled 5/8 " diam., then 13/16 "
finally ground with stones in drill - no fun
The hole ended up about 1 inch diameter.
These two efforts increased the take off
can do a wheelee -- whee
& top end went from about 23 to about 30 mph
Hooray for us
keep up the good work here

