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Post by jtron on Apr 4, 2016 22:16:36 GMT -5
So I got a new tach for my gy6 150 and was testing it out. I tried to set it on the 1 spark/rev setting because although the gy6 is a 4 stroke, it has a wasted spark right? Well on that setting it only read around 800-900 or so rpms at idle, but wouldn't the motor barely be running at such a low rpms? When I set it to 1 spark/every other revolution it read around 1700-1850 rpms which seems more normal for a gy6 from what I've read. I'm pretty confused, because I thought a 4 stroke with a wasted spark would fire 1 time/rev...what am I missing Here?
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Post by rcq92130 on Apr 4, 2016 23:16:25 GMT -5
You now have it set correctly.
You want it to COUNT 1 spark for every 2 revs. Counting every spark would be proper for a 2-stroke.
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Post by rockynv on Apr 4, 2016 23:20:29 GMT -5
1000 to 1500 for a 150 is the norm depending on your tune. Is it creeping right now? Whats it reading at 50 mph?
I do not believe the average 150 has anything reading the cam to tell when its on the compression stroke nor has any feedback from the coil to gather that information so it should spark at every rev since it does not have a cam driven distributor or a magnetic pickup on the end of the camshaft or any other means to tell the difference between a compression stroke or exhaust stroke. If you take the plug out and crank the engine with the base of the spark plug grounded against the block with the high tension lead connected you should see whether it sparks on every revolution or not.
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Post by jtron on Apr 4, 2016 23:40:55 GMT -5
I still have to mount it so I haven't ridden with it on, just hooked it up at idle to see if it works ok. I guess I'll have to try both settings at speed once I mount it. I thought it was strange though that it was reading below 1k at 1spark/rev because most ppl say their scoot dies before it gets that low. My idle doesn't sound slow at all, no stumbling, it's pretty steady at idle.
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Post by rcq92130 on Apr 4, 2016 23:47:31 GMT -5
There is basically no way to get a 1-cyl GY6 engine below 1K and have it running. Even getting a standard China built GY6 below 1500 is a challenge. Normal idle for a 150 is 1700 or 1800, unless you have a BBK (then slightly higher).
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Post by jtron on Apr 4, 2016 23:56:58 GMT -5
Cool, that's what I've been reading. It's just strange that all the threads I've read say for a gy6 it would be 1 spark/rev due to the wasted spark, but mine seems to be reading accurately at 1 spark every other rev. Well ill see if the rpms look normal at speed once I get the thing mounted
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Post by hillbillybob on Apr 5, 2016 7:35:43 GMT -5
The second setting you tried is the correct one. You won't get a gy6 150 to idle at 800 - 900 rpm's. Much below 1500 gets a bit unstable on mine, and I know it's tuned correctly to deliver the the fuel mileage it does, not to mention that it's still running the original spark plug with 9,100 miles on it.
And, they do produce a wasted spark......your tach's setting buttons must have left hand threads...or something like that
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