Single Tooth pickup

[trailrunner]

I am looking to squirt a few atvs and would like to do both fuel and spark control with the microsquirt. Problem is that to make a 36-1 wheel work would prolly run a extra $200 in machine work and that makes spark hard to justify. The bikes I want to squirt all have a single tooth pickup that is fairly long and the falling edge of the tooth is TDC. Could this be made to work well or am I stuck running the factory ignition system and just using the factory crank sensor for a tach input? Thanks!!!

[Matt Cramer]

This could work for an even fire parallel twin or a one cylinder, though it could suffer from low resolution issues.

[Andy_Stprbeck]

On my WR450 i am looking into using the magneto output as effectively a 12 tooth crank wheel, with the stock vr sensor as a crank ref.

There is a fellow over on the MSEFI boards who has a YFZ450 for which he made a missing tooth cam wheel that looks like it works pretty well. Lots of info there about the advantages to using the cam wheel for timing of the map reading on a speed density setup. Looks to me like that is at least a less involved project than adding a crank wheel if your engine is anything like mine. Search for "MYK777".

[SQLGUY]

I tried the stock reluctor, a custom 1 tooth wheel, a custom 8-1 tooth wheel, and finally a custom 36-1 wheel on my Yamaha motorcycle. Details are here: http://residentialcolorado.com/SECA_750i.htm

Basically, I found that with a single tooth, idle timing may have as much as 20 degrees of error. In retrospect, the 8-1 wheel probably would have worked fine... I did the 36-1 wheel to try to solve synch problems that eventually actually required electronic modifications to Microsquirt's VR conditioner circuit.

Also, with the single tooth, at least in my system, that meant using dual tachs, which, while workable, has some definite quirks to it (dwell restrictions, base trigger offset tricks, etc).

Cheers,
Paul