ok, this is what I have come up with on my motor as far as ignition timing...
I have two motors im using for reference, a standard 900 twin and the 1500 triple... Im learning some things as I go along so hopefully others can too! Figuring out ignition/timing curves is kind of a lost art anymore in two stroke performance but I think its HUGE when it comes to how a sled runs, and also why some sleds run better than others out of the box... When I had my tcat flywheel re-tapered/re-keyed it was measured by a machine that was accurate within less than .0001" the difference between one mass produced flywheel to the next was scary!
Just to give some measurements...
Here is the triple... MAG cyl at TRUE TDC, zeroed on the bore gauge and a degree wheel...
This is where at the same TDC, where my modded tcat flywheel trigger comes across the ignition sensor..
This scared me a bit, I was under the impression that it would be more toward the center... NOPE! BUT...
This is where the STOCK 900 is at the same TRUE TDC
Here is where the leading edge of the TRIPLE flywheel trigger hits the ignition sensor... Notice how many degrees I rotated the engine backwards to get the trigger to this point (4 degrees) yes it looks like more but the angle I had to take the pic at makes it look like like 5 you can also tell this flywheel has two flywheel keyway slots in it (modded tcat) Look at the welding rod "pointer" in relation to the degree wheel
Heres the twin in the same configuration, (no welding rod pointer just a sharpie, sorry) the angle of my phone was goofy to get this pic without getting any glare but its still at the same 4 degrees ATDC to intersect at the same leading edge of the flywheel trigger on the TWIN un-modded flywheel... I used the leading edge of the flywheel trigger as a reference since thats about the only thing similar between the two flywheels to use as a common measuring point between the two engines...
Now as far as static timing goes on the bench this is about as close as you can get... the true test is timing advance with a timing light at rpm so heres some timing marks (5 deg... have to make single degree increments still) on the clutch once this motor is spinning.
Since Scott has left this info in another forum I have done the work to bring it over to good ol' snowest!
Thanks Scott!!!
Now, to make the twin CDI work, at minimum it needs to be reprogrammed to make the RPM correctly correspond to timing advance since now were dealing with 3 flywheel triggers instead of two, (the CDI thinks 1000 RPM's is now 1500, 1000x's 1.5) So obviously an un-reprogramed twin CDI wouldnt have the correct ignition advance as RPM's increased. Scott has the answer to that along with some new timing curves to the original twin ignition timing curve itself! Ill let him comment on that if he wants.
Honestly Im hoping to be around the 14-16 degrees BTDC on this engine at the low 8000 rpm mark, Scott has sent me a re-programmed CDI that has an extra 2* of ignition advance at higher RPM's, the trick is going to be getting around the hot timing in the mid range the twins are known for but him and his dad have another curve they're working on to combat that issue as well!
