ninjette.org - View Single Post - Spark plug problem. Tried everything I can think of.

DannoXYZ · May 1st, 2018, 01:13 PM

Using one ignition-trigger for both would work if cylinders fired evenly. But they don't with 180-degree crank. So needs separate triggers and timing for each cylinder.

Notice that both cylinders are doing wasted-spark, firing on both end of compression and exhaust strokes:

0 compression -> spark -> BANG
180 compression -> spark -> BANG
360 exhaust -> spark -> puff
540 exhaust -> spark -> puff

0 compression -> spark -> BANG
180 compression -> spark -> BANG
360 exhaust -> spark -> puff
540 exhaust -> spark -> puff

and so on... hence the uneven firing sound at idle.. BBbrruup... BBbrruup... BBbrruup

To get perfectly even firing order, you'd need 360-degree crank (both pistons go up & down together), but you'd end up with horrible primary balance.

May 1st, 2018, 01:13 PM	#7
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	Using one ignition-trigger for both would work if cylinders fired evenly. But they don't with 180-degree crank. So needs separate triggers and timing for each cylinder. Notice that both cylinders are doing wasted-spark, firing on both end of compression and exhaust strokes: 0 compression -> spark -> BANG 180 compression -> spark -> BANG 360 exhaust -> spark -> puff 540 exhaust -> spark -> puff 0 compression -> spark -> BANG 180 compression -> spark -> BANG 360 exhaust -> spark -> puff 540 exhaust -> spark -> puff and so on... hence the uneven firing sound at idle.. BBbrruup... BBbrruup... BBbrruup To get perfectly even firing order, you'd need 360-degree crank (both pistons go up & down together), but you'd end up with horrible primary balance. Last futzed with by DannoXYZ; May 1st, 2018 at 02:21 PM.