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Discussion Starter #1
Does anyone know how much horsepower the old 521cc motor made?  A dealer told me that the sled made 98 horse.  Does this sound too high to anyone?  Mike

P.S.  Anyone hear if winter is ever going to get here? Sad, but with this crap I'm ready for spring already.  
 

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BlackKnight
Your dealer is in the Ball park,i have a 85 plus with
that engine and used to talk to the boys at FAST,
they told me those engines made around 96hp.I gave
mine a .049 sqish, polished exhuast ports and geared
down to 22-38 from 26-38,no overdrive in these babies.
This old sled is fast,it will run about 155km if you give her
a little room,and it used to out drag every thing up until the
94Machs came out. I still have it and keeping it as a collector
as 85 was the first production independant front end for bombi as far as i know.
                           hope that helps
                              GREYGOAT
 

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THE FIRST FOUR YEARS OF PRODUCTION THE 521 MADE ABOUT 88 HORSE. THE 85-88 MODELS HAD 40 MM CARBS. IN 89 THEY GOT DETUNED BECAUSE OF THE 583 IN THE LINE-UP.
 

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Discussion Starter #4
Thanks guys.  If you know of any sites showing these numbers let me know.  

Greygoat, I have a 1986 Plus that when new just destroyed everyone I rode with.  But that was then.   
 Thanks.  Mike
 

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I used to have 86 F Plus. Greatest sled I have ever own!!! Bought used for $1300. When new, the guy took it to HRP and had Brad Hullings do the treatment! Pipes, porting, 580 big bore, 44 carbs K+Ns, the whole works! I bought it, filled it with gas, and took it out on our lake and could smoke the new Wildacats and VMax 750s all day long!! WIsh I still had that old tank!
 

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Mxzr
You could be right there,but i rode one of those Blizzards
a freind had and his wasn't much of a sled.Do you think we should count it.
                      GREYGOAT
 

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DYNOTECH HAS STOCK AND MOD HP RATINGS FOR THE 521. THEY ARE INCLUDED IN VOLUME 1 ISSUE 1. THEIR ADRESS IS 8 APOLLO DR. BATAVIA NY 14020. THOSE ARE GOOD MOTORS. MY BUDDY HAD AN 87 THAT CHEWED 650 INDY'S AND WILDCATS. GOOD LUCK.
 

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Hello    

As far as I know, the ROTAX 521 cc Engine came in four (4) different versions.

they were called as followed:

* 532   ( Safari Grand Luxe LC  -86 )
* 534   ( I think this is the same engine as 537, but with Magnesium crank case ! )
* 536   ( Formula Plus 89-92 )
* 537   ( Blizzard 9700 83-84 , Formula Plus 85-88 , Formula Plus 500 -90 , Formula Plus-X -91 )

Hp example:

-87 Formula Plus ,  "537"   2*VM40  = about 95 Hp. / 7800-8000 rpm
-90 Formula Plus ,  "536"   2*VM34  = about 60 Hp. / 6900 rpm
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Does anyone know which type of RV-disc and jetting that were mounted in these two sleds ? :

* Formula Plus 500  -90
* Formula Plus X  -91
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Sorry about the grammar and spelling !  
 

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I used to have a 87 form plus it kicked a$$.  What a change from my 78 olympique, lol
 

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Discussion Starter #11
Lasse,

The jetting for the '90 Formula plus according to my manual is 250 mains for both carbs and 159 Q-4 needle jets. It didn't say what type rotary but did show the timing.  If you want it let me know.

The '91 Plus X shows 360 mains for both carbs and and  480 P-4 needle jet for the PTO side and 480 P-2 for MAG side.  Hope this helps.

You sure about that 60 hp for the 91 plus X?  Seems way too low to me.  I thought the X model was supposed to have more power than the regular plus but less than the Mach1.

Permafrost - You said it.  I went from a cheetah 5000 to the 86 Formula plus.  To me, at the time, it might as well have been a Mach Z.  

Mike
 

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Blackknight / Mike & Others


All Formula Plus 89-91 had the "536" engine. 2*VM34

But,  As a HO alternative Ski-Doo made this machines in some kind of "LE" models:
* -90 , Formula Plus "500" with the "537"  ,  2*VM38
* -91 , Formula Plus "X"  with the "537"  ,  2*VM38

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They were never imported to Europe, but still my friend has one of these in his garage !!
We are trying to rebuild it 100%, but we have difficulties to find any tech. specs. on this machines !!!
Thaths why I need help !!

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The Rotax RV-engines with "End" outlet pipe always have bigger basic jetting on the MAG side !!
And the RV-engines with "Center" outlet pipe always have bigger basic jetting on the "PTO" side !!

I think you must have miss read the tech specs.......

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Compared to the ordinary Formula Plus with "536" ( 2*VM34 ) and about 60 Hp. this machines with "537" and 2*VM38 had about 85 Hp !!

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Please, help me out with my problem about the jetting and the RV-disc on this machines.........

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Sorry about the grammar and the spelling !!  
 

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Hello Lasse
  I thought i had spec. book on those sleds but just had
  a look and my book only goes to 89 model year.If you
  like go to www.mrrsltd.com/ their e-mail adress is there
  ask for Ken he'll likely help you out.
                                    GREYGOAT
 

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Discussion Starter #14
Lasse,

The numbers I gave you are correct, or at least what is printed in the manual.  Clymer Ski-doo shop manual, 1990 - 1995, page 142.  You can find it all over the internet, like amazon.com.  If you want to know more specifics, email me.  Mike
 
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