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Post by rcq92130 on Jun 30, 2015 19:38:38 GMT -5
But, then, at the low end if you actually can tune your beast well enough to get it to idle without dying at an indicated 1,200 (near super human) ... you think the thing is actually idling at 600 rpm  That's impossible for a 1 cylinder engine. |
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Post by rcq92130 on Jun 30, 2015 21:42:08 GMT -5
Briggs & Stratton Idle Speeds
Model Series Type Idle Speed ( rpm )
60000 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
80000 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
90000 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
10A000 Thru 10M000 L-Head Aluminum/Cast Sleeve Single Cylinder None
110000 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
120000 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
130000 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
170000 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
171700 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
190000 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
191700 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
220000, 250000 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
280000 L-Head Aluminum/Cast Sleeve Single Cylinder 1750
230000 L-Head Cast Iron Single Cylinder 1200
240000 L-Head Cast Iron Single Cylinder 1200
320000 L-Head Cast Iron Single Cylinder 1200
400000, 420000, 460000 L-Head Opposed Twin Cylinder 1400
50000 OHV Single Cylinder 1500
85400 OHV Single Cylinder 1300
97700, 99700 OHV Single Cylinder 1500
115400, 117400, 118400 OHV Single Cylinder 1300
120000 Horizontal Shaft OHV Single Cylinder 1750
120000 Vertical Shaft OHV Single Cylinder 1750
138400 OHV Single Cylinder 1300
185400 OHV Single Cylinder 1300
200000 OHV Single Cylinder 1750
210000 Horizontal Shaft OHV Single Cylinder 1750
210000 Vertical Shaft OHV Single Cylinder 1750
235400, 245400 OHV Single Cylinder 1300
280000 OHV Single Cylinder 1750
310000 OHV Single Cylinder 1750
290000, 294000, 303000 OHV Twin Cylinder White Governed Idle Spring: 1100 / Red Governed Idle Spring: 1400
350000 OHV Twin Cylinder White Governed Idle Spring: 1100 / Red Governed Idle Spring: 1400
380000 OHV Twin Cylinder White Governed Idle Spring: 1100 / Red Governed Idle Spring: 1400
405000 OHV Twin Cylinder 1750
445000 OHV Twin Cylinder 1750
540000 OHV Twin Cylinder 1500
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Post by rcq92130 on Jun 30, 2015 21:45:54 GMT -5
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Chinese tachs
by: stellarfoxy - Jul 1, 2015 9:01:50 GMT -5
via mobile
Post by stellarfoxy on Jul 1, 2015 9:01:50 GMT -5
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Post by steve on Jul 1, 2015 13:06:43 GMT -5
I have a CDI that has an LED that flashes every time it fires. I got my scoot idling to where the stock tach said about 1100 RPM. You can count the flashes when you are turning it over to start it. Once it starts idling, when the tach says 1100, or less, that thing is flashing VERY rapidly. I borrowed my mom's digital video camera, and it will slow down to 1/2 speed, and it is still firing so fast you can't count it. I bet it is flashing 15-20 times a second. The only way to tell that it is just not lit up solid is if you watch it when you are cranking it, and you can see how bright the light actually is when it lights.
I'm going to take the fan off, and look at the flywheel here pretty soon.
I would say the tachs are close to right.
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Post by steve on Jul 1, 2015 13:08:44 GMT -5
I would think that multiple cylinder engines can idle at a lower speed than single cylinder engines.
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Post by rcq92130 on Jul 1, 2015 13:59:13 GMT -5
I would think that multiple cylinder engines can idle at a lower speed than single cylinder engines. Yeah, of course. An 8 cylinder fires 8 times more per rotation than do our little fly fart engines. Less time between firings means it can sustain a lower RPM. |
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Post by rcq92130 on Jul 1, 2015 14:06:30 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). Actually these scoots fire on every revolution. They fire at tdc each time it hits Tdc, but there is only ignition on every other spark. So every full revolution down then up , the plug fires. So every other spark is wasted. Just to repeat - neither of us are "arguing"; just trying to understand. This one i don't get. Your question isn't about the accuracy of the tach (i.e., if it's off 5% or 15%) but about the setting - is the tach reading half (or twice) the real rotational speed. But looking at both possibilities does not make sense to me ~~~ 1. Tach is reading twice the actual speed: That would mean when the tach says the engine is at 1400 RPM the engine is really at 700 RPM. But that's impossible. 2. Tach reading is half actual speed: That would mean when the tach reads 8,000 RPM the engine is really at 16,000 RPM. That's also impossible. In fact, if you are using a digital display tach the error is going to be very, very small (unless you are using an inductive pickup - "sense" wire wrapped around spark plug wire - in which case some sparks could be missed. The "counter" inside the tach is a simple IC and will count properly unless there is a defect. There could be a calibration error if your tach displays analog RPMs, but that would be ... what? ... 5% maybe? It's really fun when you latch onto things and uncover things no one knew ... but for tachs i just don't get how there can be an issue. Help me out here ..... |
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Chinese tachs
by: stellarfoxy - Jul 1, 2015 21:53:37 GMT -5
via mobile
Post by stellarfoxy on Jul 1, 2015 21:53:37 GMT -5
this might help the discussion. at times during the video my tach says it's idling as low as 500 rpm (closer to the beginning and very end). this apparently isn't possible. but upon revving it will go easily to/past 7000. it obviously isn't going 14000, so mines not reading half, yet...
so what's up with my tach? also this is the first thing I've ever shot/edited/uploaded entirely on a cell phone, sorry for the poor quality.
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Chinese tachs
by: geh3333 - Jul 2, 2015 17:45:29 GMT -5
via mobile
Post by geh3333 on Jul 2, 2015 17:45:29 GMT -5
I think rcq made all those number up !! He is always trying to make me look dumb . anyway I looked up his numbers and he must have infiltrated the web, because that's pretty much what every other site is saying also.
Lol, I'm sure your right rcq . Id still like to see an actual test. Somehow my scoot was idling almost right at 1000 rpms yesterday !! I'll have to take a video. And my darn speedo cable broke again!! I ordered the wrong one and had it rigged up . so I guess I need the right one .
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New Rider
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Chinese tachs
by: stellarfoxy - Jul 2, 2015 17:54:12 GMT -5
via mobile
Post by stellarfoxy on Jul 2, 2015 17:54:12 GMT -5
I know my speedometer is way off. it said I was going 70+ mph at 5500ish rpm. the speed limit was 45, I was behind a car. I think my whole cluster is messed up.
any chance that at low rpm the tach misses some signals and can read low but once it's revved the signals are stronger and it reads more correctly?
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Post by rcq92130 on Jul 2, 2015 17:58:58 GMT -5
Not possible the tachs are doubling the actual engine speed .... otherwise they would be showing 15K or 16K at WOT. Unless the actually rpms are 1/2 what they are reading. I mean if the engine is actually idling at 700- 850 rpms . then the stock TACHS double that. I know its a long shot but if I'm reading the exhaust right , hats what's happening. OK, George, I think I have some info for ya. The digital (and analog) tachs are hooked up. Here are 3 photos of what they read at idle (I have it set to 2,000 on the analog tach), 4,000 rpm and 6,000 rpm.    The digital tach is no doubt dead nuts on since it's got no display error (the analog one does, since the movement of the needle has to be calibrated to the pulse count). You can see the analog tach is almost perfect at 6,000 rpm. My guess is that's where they calibrated it. At lower speed the analog tach gets progressively less accurate. at 4,000 rpm it reads high by 220 rpm, or about 6% at 2,000 rpm it reads high by 395 rpm, or 25% (which is terrible! China!) So, while I thought I had my idle set to 2,000 it was really idling at 1,605. Hope this helps. |
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Post by linton on Mar 27, 2016 1:31:36 GMT -5
Hi, I have had the same problem since new on my Chinese build Riya Adonis 300T scooter. RPM needle bouncing at idle and needle struggling at high revs. My solution was, I installed a 6A10 6A 1000V Diode on the trigger wire direct from ignition coil ( yellow / black wire ) and another under dash going to tachometer ( white/red wire ). This leveled out the signaling instability issue I was having. Was wondering if anyone else had tried this method or another better solution, would love to hear from you!!!!
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