Mach Z Timing Curve? - Snowmobile World : Your #1 Snowmobile Forum

GlennM · 10-29-2002, 11:14 PM

Hi does anyone know the timing curve for a mach Z ?. I know on my 200 Mach Z std at 3500 rpm it is about 18 deg BTDC but what is it at higher rpms ?

thanks for any help

Glenn

Mikadoo · 10-30-2002, 06:05 PM

Where did you come up with 18 B.T.D.C.? I have the 2000 repair manual if front of me and it's .102 B.T.D.C. That's one hundred and two thousands. The ONLY way you can change timing is thru the M.P.E.M. this takes some specialized equipment from your Doo dealer.
If you want to CHECK your timing to see if it's right this is what you do: Screw in a dial indicator in the Mag piston and find T.D.C. Next, put some tape on your clutch top [the 1/4 wide part] about 3" long. Next, some tape on the frame directly above the clutch then scribe a line on both, this will be T.D.C. Next, rotate the clutch back then forward to .102 B.T.D.C. and mark.
Get a regular automotive timing light, hook it to a 12V battery, plug the other wire to the mag spark plug, start sled, and hold RPM's @ 3500 and she what she reads!
I just went thru all this about a week ago so it's still pretty fresh in my mind. Hope this helps......

GlennM · 10-30-2002, 07:33 PM

Mikadoo thanks for the reply, that was 18 degrees BTDC not inches it is 1.94 mm or 0.076 inches. I understand the proceedure for 3500 rpm. But what happens with the timing nlight at higher rpm's ?.

Thanks Glenn

Mikadoo · 10-30-2002, 07:40 PM

Glenn, .076 B.T.D.C. is for the Formulalll 800 [single pipe]. As for above 3500 it will read the same, it takes that amount of rpm or more to get peak timing.

rab · 10-31-2002, 05:52 AM

The timing advances with rpm's, you can see it with a light. The mpem sleds have a flat spot in the timing curve between 3000 & 4000 rpm's so it will be stable for you to read, so they use 3500 rpm's to check it. There is a chart that is used to determine what number is entered with the programmer to get the timing you want.

Bigmac · 10-31-2002, 03:12 PM

How about timing on an older Mach-z ... 96 ?? I just changed my stator plate .... will that change my timing ? Or is it the triger switch that will change it ??

Allen Avram · 10-31-2002, 03:20 PM

I heard from a reliable source, for a 1994 Mach Z that the timing should be set at .80 to .83 thousands BTDC...this is a big difference from the stock .97 thousands...anyone have a comment on this? Al.

madsledhead · 10-31-2002, 08:11 PM

It's typical for same sled to have different specs, it all depends at what RPM you are checking it at.

All these sled have CDI with a timing advance function.

My XCR uses 2 setpoints for reference markes. One at 3500RPM (28 deg or .187" BTDC) and one at 7000 RPM (13 deg or .087 BTDC)

I don't know why, but Bombardier insists on only specifying 1 check point RPM. I just did a 98 MXZ 500 in my shop and I used 18 deg at 6000 RPM. I check with Bombardier and they don't even know what it should be at 4000 RPM? Seems to me having 2 reference points is better.

So to answer your question GlennM,

If you want to know what your timming is at higher RPM, you need to use a variable spark advance/retard timming light. {Personnaly I use the Ferret Instrument T84} This cannot be performed with a conventional spark timing gun, it has to be the timing advance gun.

Scribe a black line at EXACTLY TDC on the clutch with a pointer mounted on a fixed location pointing at your line.

Then start the engine.

Run at 3000 RPM, then click the timing advance button until your lines line up.
Then increase to 4000 RPM, click the timing advance until the lines line up again.
Keep doing this up to the RPM you want and chart you timming advance/retard curve.

Just a trick, Remove the PTO side plug, close the gap to 0 and reinstall it. This will act like a fouled plug and you will be able to hold rpm better because it wont climb as fast.

Let me know how it worked out,

john breedon · 10-31-2002, 09:12 PM

Dont quote me on this but all machs were set at .083 from the factory,98 were recalled and set to I believe at .065,and the race manual calls for an extra .010 of advance for all end outlet pipes.We did this on the old 96 780 you just had to move the trigger,after 98 you had to do it with a computer I believe.

rab · 11-01-2002, 06:24 AM

On the 98 you could still move the trigger, thats how the update was done. The fixed trigger came with the first castings that could have an rer trigger in them, those needed the programmer to chnage it. The retarded ignition in 98 was to help get the side outlet pipes hotter. The timing flat spot between 3500 & 4500 on mpem units is so the timing won't jump around and you can see it. They can change the timing curve with the mpem at different points.