Sorry leo, but if you read into it a bit, I thought the HD200 motor was a 2 spark per revolution motor like most GY6s' but it isn't. I ordered the wrong one that only registers 1 spark per revolution instead and thought I'd have to return it and get the other one. I didn't... The HD125/200 motor is in fact a 1 spark per revolution motor.
There are advantages and disadvantages to this and I'll explain it below a bit.
1) Generally most gasoline motors and engines have only one ignition/spark per cycle. A four stroke motor, like the HD has 4 seperate phases (strokes) per cycle. The ignition or spark occurs on the ignition phase only in this design.
2) I'm an Auto Mechanic and I can tell you that over 90% of cars on the road today fire (spark) two times per cycle. Along with the normal ignition stroke, they also fire on the exhaust stroke. This is mainly done for one reason only and that is to try and burn off more fuel that wasn't used initially on the ignition cycle and to meet emissions standards.
3) Today's efficient motors/engines usually fire on both strokes and here's a quick example; Any GM 3.1, 3.3, 3.4, 3.8 is a V-6 but only has 3 ignition coils. Each coil has 2 cylinders attached to it and each coil fires 2 cylinders at the same time. One fires on the igniton cycle and the other connection is on the exhaust cycle on another piston. More and more engines are switching to a single coil on each cylinder and also firing on both strokes.
4) Race/ performance engines don't need to fire on the second stroke as emissions aren't an issue. Without a doubt a ignition coil, like everything else, has a MTBF (Mean Time Before Failure) and if it's working double-time, well... you do the math.
5) The HD motor is a high performance motor for sure and it's made for longetivity. Since it is a 4 valve design, fuel efficiency is optimal and the need for a second spark on the exhaust cycle isn't necessary.
Sorry for ranting and raving but I'm just glad to get my computer back after I replaced the motherboard because it's "MTBF" decided to kick in
In so few of words Raphael--- The HD 125/200 motor sparks one time per cycle and not revolution. There are 4 strokes (revolutions) per cycle; Intake, Compression, Ignition and Exhaust. If you want to get an EMN tach then you'll need the PT15E2 model.
Here's the link to the one you (we) need and hope this helps---
http://enmco.thomasnet.com/item/enm-counting-instruments-tach-hour-meters/tach-hour-meters-pt15-tachometer/pt15e2-2?&seo=110PS I bought mine from eBay cheaper so shop around.
