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Chinese tachs
by: geh3333 - Jun 25, 2015 23:36:27 GMT -5
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Post by geh3333 on Jun 25, 2015 23:36:27 GMT -5
How's it going. I saw an old SD post about idle rpms. The old member said he had a few different scoots and one called for a 750 idle rpm. We have a member who is having an issue with his scoot and he can get his scoot to idle as low as 500 rpms !! I watched the video and I noticed his idle rpms did not seem any lower then 1300-1700 rpms. When he hits the throttle and the rpms raise to 2000 rpms , his rpms sound much higher then 2000. My scoot idles around 1700 -1800 rpm sometimes a little higher and sometimes a little lower. It just depends on the outside temp. I can get it to idle as low as 1300 at times , but at that point its nearly shutting down . his sounds the same , but at 500 rpms . the problem I see , is that his tach still redlines at 8000 rpms . meaning , if his tach is off , then at 8000 rpms he is about 1000 rpms or so higher.
I wonder if most of our TACHS are not correct. I mean at 1300 rpms my scoot is barely running , but is still at 1300 rpms!! To be honest his 500 rpms sounds a little more believable. When you can just about watch a spot on the variator spin without loosing that spot , how is it still spinning at 1300 rpms ? 500 seems more accurate. Can some of these TACHS be reading the rpms different ? Both are gy6 157qmj engines , so how can one call for 750 idle rpms and another call for 1700 idle rpms ? I think its worth investigating.
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Chinese tachs
by: geh3333 - Jun 27, 2015 6:39:03 GMT -5
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Post by geh3333 on Jun 27, 2015 6:39:03 GMT -5
No one wants to bite ?
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Freshman Rider
Currently Offline
Posts: 96 
Likes: 10
Joined: May 4, 2015 14:22:19 GMT -5
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Post by nimajneb on Jun 27, 2015 15:31:51 GMT -5
My scoot does not have a tach. But i tried to hook one up for temp use(for this thread) but i could not get it working so im going to take the tach apart and see if some wires are messed up.
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Chinese tachs
by: JoeyBee - Jun 27, 2015 19:53:47 GMT -5
via mobile
Post by JoeyBee on Jun 27, 2015 19:53:47 GMT -5
geh3333, I have been curious about the accuracy of my chino tach also. My 157QMJ wants to be around 1800RPMs also. Any lower it sputters and is unhappy. Do you want to test out the accuracy? We can both order a tiny tach and share our results.
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Post by keikara on Jun 27, 2015 21:00:40 GMT -5
My scooter will idle very nice when the tach says between 1800 and 2k, however I have had it idling at about 800 without dying it almost wants to and sometimes will stall, but more times than not it will idle and I can rev and takeoff with it at 800 rpms, also my clutch seems to start grabbing just over 3k on the tach.
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Chinese tachs
by: murkyapricot - Jun 27, 2015 23:46:06 GMT -5
via mobile
Post by murkyapricot on Jun 27, 2015 23:46:06 GMT -5
Mine can go as low as 1k and be just on the verge of cutting off but it seems like my best performance is idle just under or on 2k
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Chinese tachs
by: geh3333 - Jun 28, 2015 1:23:06 GMT -5
via mobile
Post by geh3333 on Jun 28, 2015 1:23:06 GMT -5
My main concern about our TACHS is , even when the engine is idling so low that its on the verge of cutting out , its still at or above 1000 rpms . I had mine idling at 1200 today and it sounded very low . I doubt the engine is actually running at 1200 rpms when its nearly cutting out. It sounds much lower. Ixf someone has a way to test the rpms some other way , that would be great.
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Post by steve on Jun 28, 2015 16:56:23 GMT -5
My CDI has an LED that lights every time it fires. I wonder if we could video it, slow the vid down, and count them. We would just have to count for 1, or 5 seconds. It would have to be somebody who is better at messing with videos than me, though.
We could do the same with the flywheel. Slow the vid down, and count how many times it goes around. Mine idles at about 3K, now that I installed the BBK. It's probably the advanced angle CDI that makes it cut out at lower RPM.
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Chinese tachs
by: geh3333 - Jun 28, 2015 23:16:01 GMT -5
via mobile
Post by geh3333 on Jun 28, 2015 23:16:01 GMT -5
My CDI has an LED that lights every time it fires. I wonder if we could video it, slow the vid down, and count them. We would just have to count for 1, or 5 seconds. It would have to be somebody who is better at messing with videos than me, though. We could do the same with the flywheel. Slow the vid down, and count how many times it goes around. Mine idles at about 3K, now that I installed the BBK. It's probably the advanced angle CDI that makes it cut out at lower RPM. If you can do that , it would be great. That way you can compare your numbers to your tach. |
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Post by steve on Jun 29, 2015 10:52:35 GMT -5
My CDI has an LED that lights every time it fires. I wonder if we could video it, slow the vid down, and count them. We would just have to count for 1, or 5 seconds. It would have to be somebody who is better at messing with videos than me, though. We could do the same with the flywheel. Slow the vid down, and count how many times it goes around. Mine idles at about 3K, now that I installed the BBK. It's probably the advanced angle CDI that makes it cut out at lower RPM. If you can do that , it would be great. That way you can compare your numbers to your tach. I don't know if I know how to slow it down. I shall try. |
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Chinese tachs
by: geh3333 - Jun 29, 2015 16:19:36 GMT -5
via mobile
Post by geh3333 on Jun 29, 2015 16:19:36 GMT -5
That would be great.
My main problem is that both engines are a gy6 150. Why would one call for 750 idle rpms and one call for 1700 idle rpms. That's a big difference. The only thing that can be different is that they are using different TACHS. When one is idling at 700 rpms and it sounds the same as the other scoot idleing at 1700 rpms , we have an issue. I would not be surprised if most of these TACHS are not correct.
I have an idea. You can feel every exhaust stroke by putting your hand over the exhaust. You can do a ten second timer and count the amount of exhaust strokes. You would then have to multiply that by two if I'm not mistaken.
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Post by rcq92130 on Jun 29, 2015 16:31:42 GMT -5
There is zero chance a GY6 engine would idle and not quit at 750 RPM.
Sorry - that is the real world.
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Chinese tachs
by: geh3333 - Jun 29, 2015 17:30:13 GMT -5
via mobile
Post by geh3333 on Jun 29, 2015 17:30:13 GMT -5
There is zero chance a GY6 engine would idle and not quit at 750 RPM. Sorry - that is the real world. Here are my results . at 1200-1300 rpms , the exhaust is opening 4 times a second. So that would be 8 rotations a second. 8x60 is 480 rotations a minute . 1200-1300 rpms is well below recommended idle. So at 1700 rpms it should be pretty close to 700 - 750 rpms. Can someone do the same test and verify this. We can see his scoot is reading 500 rpms at times . this is pretty interesting. |
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Chinese tachs
by: geh3333 - Jun 29, 2015 17:32:52 GMT -5
via mobile
Post by geh3333 on Jun 29, 2015 17:32:52 GMT -5
At 1200-1300 rpms , you can clearly feel and hear the exhaust strokes.
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Chinese tachs
by: geh3333 - Jun 29, 2015 17:43:11 GMT -5
via mobile
Post by geh3333 on Jun 29, 2015 17:43:11 GMT -5
Hey dmartin , is there a way you can test this with a timing light and get an accurate reading ?
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