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Discussion Starter · #1 ·
Hey guys...

I'm looking to get a little more power out of my buddies 98 Formula 670, and nothing to major, but just wondering if anyone out there has done some jetting and spring changes to get some power out of these motors.

We want to keep the mods cheap, so just some clutch springs and little bit of carb work....so if any of you out there have done things and have the #'s or colours to use let me know..

Thanks in Advance...
 

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my 97 mxz 670 is running

pink and white front spring with 280 ramps

biege rear spring set on highest tension a6 i think

dropped 2 teeth on my top sprocket

dropped my needles 2 notches


this sled will stay with almost any new sled on the trails and is a blast to ride.

if you want more you can change to a 502 rotary valve and rejet
 

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Discussion Starter · #4 ·
Originally posted by slednexxx@Oct 18 2005, 06:10 AM
my 97 mxz 670 is running

pink and white front spring with 280 ramps

biege rear spring set on highest tension a6 i think

dropped 2 teeth on my top sprocket

dropped my needles 2 notches
this sled will stay with almost any new sled on the trails and is a blast to ride.

if you want more you can change to a 502 rotary valve and rejet
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[/quote]


Never dropped needles before..what does that do , and i would imagine their cheap....and that you put the springs in..those are not the factor colours?
 

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MXZ 670cc

Perform Y-pipe modifications for a 4 HP gain
(see: Y- pipe mod’s for 670cc)
Shim cylinders up with 8mm base gasket
and adjust head clearance to .065 squish

Update tubes to 224-AA-3
Rejet carbs to 98 Update

Stock 97 98 Update
PTO 300 310
MAG 270 290

Rotary valve:
- cut or change to a 501
- time at 146° - 76°

Clutching:
- ramps, stock are 286, change to 280
- clutch spring "Erlandson" yellow 240-320
- set clicker so max. rpm is 7900-8000
- secondary clutch: set at C-6 or B-1 (16lbs)

Gearing: change to 26:42, stock is 26:44

NOTE: Airbox modifications are not recommended !!

To MAXIMIZE above mod’s:
Tunnel port crankcases and match cylinder heads
Tunnel port reed boxes, polish exhaust port

MXZ 670cc "Y" Pipe Modification

A Cut off the two spring clips carefully for re-use
B Cut beside original weld leaving just enough lip to re-weld
C Make second cut ½ in. from 1st cut and re-weld pipe
D Re-weld spring clips so that distance from tip of spring clip to tuned pipe marry-up is 1 1/8 in. (
 

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dropping the needles make the sled run leaner they are really fat from the factory. also those are the factory colors

pink and white= stock mid 90'5 mach1 670 spring

beige is stock mid 90's for most of skidoos perfomance sleds
 

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Discussion Starter · #7 ·
Originally posted by slednexxx@Oct 19 2005, 11:19 AM
dropping the needles make the sled run leaner they are really fat from the factory. also those are the factory colors

pink and white= stock mid 90'5 mach1 670 spring

beige is stock mid 90's for most of skidoos perfomance sleds
<div align="right">index.php?act=findpost&pid=940327
[/quote]


I always thought the jets were the way to go to lean it out a little... never done needles, but I guess it'll work too.

God advice everyone..we'll be getting some clutch/gearing
parts ordered soon!! :div20:
 

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Discussion Starter · #8 ·
Ok just a little foggy after a few days on some of the info...

I was wrong the sled is a 98 Formula 670 no ho

So what springs are stock for the primary and secondary, and what changes have worked for you guys..

The gearing I have all figured out, and we will drop the jets 1 size, and I will see if I can get my hands on the manifold off a 670 HO... anything else that does not require touching the motor?
 
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