More Ignition Timing
The ignition timing has to be set somewhere between 1.8 mm's BTDC and 2.2 mm's BTDC. This can be accomplished by using a Hinson Adjustable counterbalance shaft holder. You can also set it that way with a CR250R ignition. You'll find that if the chamber shape is very good, the engine will run well at settings closer to 1.8 mm's BTDC. Obviously, the least amount of initial advance is best. Always. For tuning purposes you might find it helpful to know that more advance (moving toward 2.0 to 2.2 mm's BTDC) will favor bottom end power and less advance (1.9 to 1.8 or less) will favor top end power.
When using the Hinson adjusters I have found that they are more accurate than the stroker crankshafts. That is, a +5 mm stroker doesn't always have its crankpin relocated in exactly the same place. In fact it is never in the same place. Because of that I can not tell you to drop in a +5 mm stroker and set the timing to the second scribe line below neutral (or another setting). It turns out that each crankshaft must have its ignition timing set up specifically for it. Every new stroker crankshaft has to have its adjuster plate dialed in to zero. And timing marks have to be referenced on it. This insures that the engine will be running in the appropriate range by giving its owner new reference points to use when dialing in the power personality. I typically mark from about 1.6 mm BTDC to 2.1 or so mm's BTDC. Going beyond 2.2 mm's or so BTDC creates a lot of piston heat and is generally not ventured past without careful monitoring of the internals.
When the trailing edge of the flywheel trigger just passes the trailing edge of the pick-up, the spark plug fires.
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