The Amery Snowmobile Club

Fine Tuning The FAST M-10 Suspension

By Bob Knutson

Polaris has now been offering the FAST M-10 rear suspensions on many of their models, there has be a large number of snowmobilers discovering what the M-10 has to offer. Those new to the M-10 will find that their previous rear suspension tuning experience doesn’t directly apply to the M-10, and there will be a learning curve of how to get the most out of their new suspension.
 While time spent tuning and adjusting any suspension will increase the enjoyment of your new scooter, it will be especially rewarding on sleds with a FAST M-10. A properly dialed in M-10 will most likely provide the best ride comfort and control you have ever experienced. In this article I will try to go over the basics of rear suspension tuning and how to apply this to the M-10.
Many Polaris dealers have little, if any, experience with the M-10 suspension, thus they are not familiar with the various adjustments or how to cure specific rider concerns. At a minimum, they should be setting up the M-10 equipped machines for the weight of the rider; the M-10 is a weight-specific suspension. Most calibrations are “ideal” for about a 25-pound range of rider weight. If you weigh 250 pounds as I do and the suspension is set-up exactly the way it left the factory, you will not be happy with the performance.
The M-10 will follow the same basic rules of physics for overall machine set up as any other skid frame, but there are some very unique differences and adjustments that you need to be aware of.  

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How to properly time a single cylinder engine.  First things first you will need a modified flashlight or continuity tester. Flat and Philips screwdrivers and some uninterrupted time.  .

Step 1

Remove recoil and starter cup.

Step 2

Find the mag wire, or the wire that goes to the points, on old skidoo twins they are blue, mine was black on a 335cc single cylinder.  Brown wire is normally ground and yellow wire/wires are for lighting coil. 

Step 3

Hook one side of flashlight circuit to the mag wire, and the other to ground.  The light will be dim when points are closed and bright when they open….the reason is the exciter coil is in the circuit when points are closed.

Step 4

Find timing marks, boy oh boy this can be fun sometimes, as not all machines have them on housing….if no marks you will have to research the timing spec before top dead center.  Let’s say it is 0.070”, you would need to use a dial indicator to find top dead, mark flywheel, then turn flywheel counter clockwise till you get to 0.070” then make your mark on case.  Every engine and design has slightly different timing, so no guessing here…. Another thing to watch for is centrifugal timing advance mechanisms.  Some older engines did not have them, so if you do have one, you will need to find out if the static timing is with the advance advanced or in the retarded mode.  See pics.  Early skidoo singles were set in the advanced mode, after 1968 don’t quote me, all were set in the retarded (just as it sits) mode.

Step 5

Check point opening with flashlight, vs. timing marks.  If light gets bright before timing marks line up, they are opening too early and you can either tighten point gap or turn stator clockwise to get the points to open later.  If the light gets bright after marks line up you will need points to open earlier, so turn stator into rotation or counter clockwise or adjust points to open more… note almost all engines will give you a spec on point gap. Most are  .012 -.018” and you really do want to stay inside the window they give you.

Step 6

Rotate engine thru a few revolutions to double check everything stayed put after tightening all screws. Then put starter cup back on and recoil and plug mag wire back into coil or into key switch and start running that vintage one lunger.