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Discussion Starter #1
Hey folks,

I have a low mileage, great condition Rotax 536 (521 cc) from a 91' Formula Plus, I've read some older posts that this is 60 hp engine?

Anyway. what are some safe engine mods?

I think the carbs are 34mm but I can't tell...I have attached a picture.

Thanks!

Jim
 

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well, chances are you are not going to find pipes for that thing, so you could try a different rotary valve, some porting(case too), and boring the carbs the guy building your engine might be able to get someone to make pipes for you not all these things are really reliable HP, but for an old engine where bolt on parts sorta don't exist anymore, its about the only way to make HP
 

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In 1988 the 521cc rotax was skidoo's screamer, with twin pipes, different rotory valve, and different carbs. ( I think they were 40 mm) THis was a very fast sled for it's day ! I'm not sure how the internal engine specs differ, but a dealer should be able to. There maybe an 1988 Plus engine for parts (and twin pipes) at a salvage place. Good Luck!
 

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i have some tips that i got from bombardier its a stage 1-2-3 mods but its in french stage 1 optmise perf without raising sound/octane
stage 2 mods with louder/hi octane
stage 3 race only/oval track formula 111

if you want me to fax them give me a fax no

the part no that thay give for the rotay valve is 420-9242-07 adjust the timming so that its opens at 141 deg avpmh and closes at 62deg appmh sory its in french :0:
 

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I have a rotary valve for a 521.
The 521 isn't like the '96 - '98 500 rotary but its still a good motor for its time. We had an '89 plus we used to race - fast twin pipes and porting, rotary valve, 40's, cut head - worked great. It really responds well to mods. We kept it that way and then we put NOS on it in '93. We sold it the next year - only problem we ever had all those years was a scuffed piston or 2.
 
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