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Chinese tachs
by: geh3333 - Jun 29, 2015 17:45:20 GMT -5
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Post by geh3333 on Jun 29, 2015 17:45:20 GMT -5
There is zero chance a GY6 engine would idle and not quit at 750 RPM. Sorry - that is the real world. That is my whole point, we've been going by these TACHS for years. Its hard to get an accurate reading at 1700 rpms , but at 1200 or so rpms its pretty easy. |
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Chinese tachs
by: geh3333 - Jun 29, 2015 18:00:22 GMT -5
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Post by geh3333 on Jun 29, 2015 18:00:22 GMT -5
At this point I cannot say I'm correct , but I think I'm on to something. Think about it. At 1200 rpms there is no way you would be able to keep count of the exhaust strokes. That would be 10 exhaust strokes every second and 20 rotations every second. At 1200 rpms you can clearly hear and feel every exhaust stroke. I know most motos idle between 900-1500 rpms . maybe I'm just flat out wrong.
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Post by geh3333 on Jun 29, 2015 18:57:18 GMT -5
I did the test again and it seemed like it was closer to five exhaust strokes every second at 1300 rpms. So that would be 10 rotations every second . 10 x 60 is 600 rpms every minute. Now that is at lower then normal idle rpms. If anyone can duplicate this test , I'd be very grateful. What you do is first try to get the rpms down to 1300 . put your hand over the exhaust . you can feel and hear every exhaust stroke. I then began to tap the exhaust with my hand " to the exhaust stroke" I counted " 12345 ,22345 ,32345 , 42345 ". I was getting about 5 exhaust strokes in each second .
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Post by steve on Jun 29, 2015 19:06:57 GMT -5
I'm going to do the CDI vid tomorrow.
But, wouldn't 2 flashes actually be 1 RPM? How do I count it?
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Post by geh3333 on Jun 29, 2015 19:15:10 GMT -5
I'm going to do the CDI vid tomorrow. But, wouldn't 2 flashes actually be 1 RPM? How do I count it? Every flash is one rpm, the plug fires on each rotation. Even though there is only one ignition every two rotations. The first down stroke pulls in the air and fuel. Then on the upstroke the piston compresses the air and fuel and the plug ignites the mixture at TDC and pushes the piston on the second downstroke. On the next upstroke the exhaust valve opens and releases the gasses . the plug fires again as the piston reaches TDC on the exhaust stroke , but with no ignition. So everytime the light flashes , Is one rotation. Every two rotations is one full cycle. And every cycle has 4 strokes , 2 down and 2 up. |
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Post by steve on Jun 29, 2015 19:40:32 GMT -5
Thank you, sir. I will count tomorrow.
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Chinese tachs
by: geh3333 - Jun 29, 2015 19:54:24 GMT -5
via mobile
Post by geh3333 on Jun 29, 2015 19:54:24 GMT -5
Thank you, sir. I will count tomorrow. I'm kinda worried that you may not be able to see every flash. Even if recorded and slowed down. Let's say you get the same readings as mine . the light will be flashing 10 times every second around 1300 rpms. A normal camera will prob not be able to record every flash. You may need a slow motion camera . |
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Post by steve on Jun 29, 2015 19:58:38 GMT -5
I probably have my idle set too high. I just hate stalling out at stoplights. I will put it as low as possible. There has to be an app to record in slow motion, right? I'm going to look.
I definitely don't think I can get it below 1700. I am going to mess with the A/F screw some more.
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Chinese tachs
by: JerryScript - Jun 29, 2015 21:10:42 GMT -5
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Post by JerryScript on Jun 29, 2015 21:10:42 GMT -5
1700-2000 is perfect.
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Chinese tachs
by: geh3333 - Jun 29, 2015 21:21:38 GMT -5
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Post by geh3333 on Jun 29, 2015 21:21:38 GMT -5
Yep , that's a perfect rpm range. I'm just curious why the engines seem to be be idling lower then what the TACHS say. |
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Chinese tachs
by: geh3333 - Jun 29, 2015 21:29:50 GMT -5
via mobile
Post by geh3333 on Jun 29, 2015 21:29:50 GMT -5
I could tape a straw to the variator and hold out a piece of string, so the stew will hit the string every rotation. If its spinning slow enough to be able to count , then we will know the true rpms.
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Post by rcq92130 on Jun 29, 2015 22:02:43 GMT -5
I could tape a straw to the variator and hold out a piece of string, so the stew will hit the string every rotation. If its spinning slow enough to be able to count , then we will know the true rpms. George --- You KNOW I'm a big fan of us researching these machines to figure out what is really going on. However ... A tachometer is a very simple thing - just an IC that counts pulses. That is about as basic as an electronic device can get. True - some may be defective and not work properly (especially if made in the land of rice & pigeon's eyeballs). But aside from the defective units, they are probably reasonably accurate. How about this - since seeing something that is rotating at a rate of 15 times every second is close to impossible ... I have TWO tachs - one digital and one analog. The digital one isn't connected right now. but as soon as I get a chance I'll hook it up also and see how well the 2 compare. The odds BOTH would be wrong by the same amount are pretty slim. That work? |
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Post by geh3333 on Jun 29, 2015 22:36:51 GMT -5
I could tape a straw to the variator and hold out a piece of string, so the stew will hit the string every rotation. If its spinning slow enough to be able to count , then we will know the true rpms. George --- You KNOW I'm a big fan of us researching these machines to figure out what is really going on. However ... A tachometer is a very simple thing - just an IC that counts pulses. That is about as basic as an electronic device can get. True - some may be defective and not work properly (especially if made in the land of rice & pigeon's eyeballs). But aside from the defective units, they are probably reasonably accurate. How about this - since seeing something that is rotating at a rate of 15 times every second is close to impossible ... I have TWO tachs - one digital and one analog. The digital one isn't connected right now. but as soon as I get a chance I'll hook it up also and see how well the 2 compare. The odds BOTH would be wrong by the same amount are pretty slim. That work? I completely understand. And I'm sure you know I'm not trying to argue about it, and I'm know your not either. Most of the digital TACHS have a setting so it will either count every fire of the plug or every other and so on. I know you know this , but it seems like the regular TACHS could possibly be doubling the rpms. With my outcome of the not so accurate test. I could have been off slightly still. I came up with 600 rpms at 1300 rpms reading on the scoots tach. That's just about half . now considering my test may be slightly off , that means there is a possibility that the stock tach is doubling the rpms. Trust me , I know how this sounds , lol. It sounds like I'm nuts , lol. I just have to get some real numbers before I can admit defeat. I may be completely wrong , but I have to know for sure. The exhaust may be throwing out double of what I'm feeling and hearing , but as of now , I'm just about certain what I'm feeling an hearing. I'm also stumped when it comes to the rpms when the scoot is just about cutting out near 1200 rpms. You can honestly just about watch a spot on the variator as its turning, and there is no chance its spinning near 1200 rpms at this time, but the scoots tach is saying , yes it is . even at 1200 rpms the crank and variator should be spinning 20 times a second. If it is really spinning that fast , you would have no chance watching a spot on the variator do rotations . even at 10 rotations its nearly impossible . sorry buddy , I know what your saying and I'm not at all saying your wrong , I just need to find out for sure, lol Thanks George. |
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Chinese tachs
by: geh3333 - Jun 29, 2015 23:08:39 GMT -5
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Post by geh3333 on Jun 29, 2015 23:08:39 GMT -5
Anyone who has one of the digital TACHS can test this easy. From what I read about them , it that they usually have two or more settings . instead of going by the stock tach and matching the rpms , find out which setting is for every revolution and set it there. This will be the true rpms. From all the posts I've read , everyone just put it on the setting that matches the stock tach. His can be counter productive if the stock tach is wrong. I've read many posts from many sites , and many say that the gy6 only sparks 2 times every 4 revolutions , which is wrong . these China builders may think since there is only one true ignition every other rotation , that that's all it fires. So they install a tach that reads double.
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Post by rcq92130 on Jun 29, 2015 23:21:53 GMT -5
Remember, these are 4-strokes so 2 revolutions of the crank = 1 complete cycle - 1 spark (and 4 revs of the crank = 2 sparks).
The tachs I have are both non-adjustable, made for 4-stroke engines. At best I can get to about 8k rpm's. Trust me - that little COX-airplane engine is NOT going 16K (and also is not only going 4 K).
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