kmhemi

Does anyone know the HP. rating of the 521 with stock exhaust?

How can I find out what year the engine was produced? All I know is that it's a type 536 That may help.

snoeproe

depends on what year/model sled that motor was in.
that motor was used for several years by skidoo. the first sled it was in was the 1983 Blizzard 9700 and had 86 hp with twin stock pipes/40 mm carbs. it was used for several years after in the Formula plus model sleds with a single pipe.
the 521 was a great motor!

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'71 Arctic Cat Panther 399
(2) '77 Yamaha srx 440's
'75 Yamaha GPX 433
'77 Arctic Cat Kitty Cat
'81 skidoo 9500 Blizzard
'82 skidoo 9500 Blizzard
'83 skidoo 9700 Blizzard
'99 skidoo MXZ 600
'06 skidoo GTX 500SS