Guest Jammerkiller Posted September 27, 2013 Share Posted September 27, 2013 Hi to all, Before renewing my entire charging system (a later story), I had just finished installing my Koso RX2 GP style meter on my '95. Everything seems to be working very well, except for two things. One, after setting the wheel circumference into the gauge (using an online calculator), I determined it's not set correctly. When I'm riding down the highway at "55", I'm passing everyone else at a considerable speed. I came up with 1884 mm for a 120/70-17 tire. Does that seem right? I guess I'll have to do the actual Koso method of marking the garage floor with tape and noting the tire rotation and distance for a full revolution. ( I was just trying to do the "lazy" method) The second problem is that my tachometer is really "jumpy". The needle will jump around sometimes while just idling, or while riding with a steady throttle. I've read that this is a common problem with Koso gauges, and that you need to add a resistor or a diode to eliminate the feedback. Before doing this upgrade, I had zero problems with the OEM tachometer. I did some online searching, and it looks like there are different cures for different bikes. Some just need resistance added in series to the RPM wire, some need a "floater" resister along with an in-line one to eliminate the feedback. I'm waiting for Koso email response to see what can be done about it. Any thoughts? Thanks, Jammer Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted September 27, 2013 Member Contributer Share Posted September 27, 2013 I have a Koso DB02r. To get the gauge to read ultra accurate I got it close with good tire circumference measurements, and then compared it to my iphone GPS (dashboard app) in my tankbag map pocket. Then just adjusted the tire circumference accordingly. For the tach, I also have a slightly jumpy tach in the middle of the RPM range, although my gauge is an all digital model. It did help to run a dedicated ground for the gauge however. This winter I will try what FinnRC36 did with his Koso RX1N gauge to cure the jumpy tach: http://www.vfrdiscussion.com/forum/index.php/topic/62316-my-3rd-gen-frankenviffer/#entry730181 Good luck! Link to comment Share on other sites More sharing options...
Veefer800Canuck Posted September 27, 2013 Share Posted September 27, 2013 120 * 0.7 = 84 x 2 = 168mm 17" = 431.8mm 431.8 + 168 = 599.8 * 3.14 = 1883.37mm circumference So you were very close. Link to comment Share on other sites More sharing options...
Guest Posted September 30, 2013 Share Posted September 30, 2013 Thanks for your responses, guys. (I must not have my boxes "checked" to receive email notification of your replies) I see that FinnRC36 programed his Koso unit to 2 stroke, 1 cyl and "hi act". I would think that would just confuse the hell out of his gauge, since he has a 4 cylinder, 4 stroke, 3rd gen. He said he hooked up the wire between the low voltage terminal and the ECU. (Blu/Blk wire from the ECU, if he used #1) I did get a reply from Koso, they are forwarding my question to tech support, and gave me a number to call. Also, the 1883.37 mm was what I came up with. I just decided to round up. But, I still don't think that small difference would account for my bigger difference in speed. Maybe my 6 magnets are not responding correctly to the sensor. Or, I need to downgrade to 3 magnets? Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted October 1, 2013 Member Contributer Share Posted October 1, 2013 With my gauge you have to tell it how many pulses there will be per wheel revolution... have you done that on yours? And Koso does say the more magnets the better as far as I know. When you figure out the tach let me know as I am curious to see your results. No harm in trying all sorts of different settings (such as 2 stroke, 1 cylinder... etc), it won't damage the gauge at all. Link to comment Share on other sites More sharing options...
Guest Posted October 1, 2013 Share Posted October 1, 2013 With my gauge you have to tell it how many pulses there will be per wheel revolution... have you done that on yours? And Koso does say the more magnets the better as far as I know. I have it set for 6P (6 pulses/6 magnets). I did have problems at first getting the speed to even register. I figured out that the magnets have a red ink mark on them which I thought would mean "Not this side out". But, turns out that's the side you want facing the pick-up sensor. I will go check to make sure that ALL the magnets face the same way. Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted October 2, 2013 Member Contributer Share Posted October 2, 2013 And they need to be very close to the pickup as well, as far as I know. Link to comment Share on other sites More sharing options...
Guest Posted October 2, 2013 Share Posted October 2, 2013 And they need to be very close to the pickup as well, as far as I know. Yes, within 8mm, I believe. And, they are. :) Link to comment Share on other sites More sharing options...
Guest Posted October 2, 2013 Share Posted October 2, 2013 UPDATE: I decided to inspect my OEM tachometer to see if it's PCB had any resistance or whatnot. Here's what I found..... The Signal from the ECU enters the PCB and goes through a diode first (D1), the a transistor and then a 20 ohm resistor (R2) before outputting to the RPM gauge. Tomorrow I will try adding a 1N4001 (50w) diode inline to see if that alone with eliminate the jumpy tach readings. If not, then I'll also add a 20 ohm resistor (1/4watt) inline and see what happens. Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted October 2, 2013 Member Contributer Share Posted October 2, 2013 Thanks for the info and the pictures. Can't say I have much to add but am curious to see if this helps. Jumpy tach needles are common on these gauges on all sorts of bikes. I know the dedicated ground made my tach much better and still want to investigate more. I wouldn't discount what FinnRC36 did to fix the issue on his gauge as he seemed to have actually fixed it. As for the strange settings he used, the 2 cycle, 1 cylinder etc... These are merely telling the gauge how many signals per revolution to expect, so depending on where the readings are coming from it can affect how many signals there will actually be detected per engine revolution (if that makes sense). Anyway, I hope you figure it out! Link to comment Share on other sites More sharing options...
SEBSPEED Posted October 2, 2013 Share Posted October 2, 2013 I have a koso gauge and spare tach parts, so I'd like to hear about how this works out.The gap called out in the Koso manual for my DB02R is 2mm (.080") or less. Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted October 2, 2013 Member Contributer Share Posted October 2, 2013 I thought I remembered seeing 2mm or less somewhere... Link to comment Share on other sites More sharing options...
Guest Posted October 3, 2013 Share Posted October 3, 2013 Okay...a quick update. (My testing time was cut short due to my long nap) I pulled the tail off the bike to quickly access the Yel/Grn RPM wire from the ECU for testing. First, I hooked up the diode, using gator clips, to the cut Yel/Grn wire. As I slowly increased throttle, I started to notice how the "erratic jumping" happens right around 2K RPM. If I pull the throttle quickly past 2K, then it seems to rev up just fine. But, If I "creep" the throttle up, then right around 2K the tach needle goes to max. I was pretty much able to do this every time. then, I placed a 22ohm resistor after the diode and repeated the test. Same results. Before calling it a night, I swapped out the 22ohm resistor for a 560ohm one. Not as much "erratic" behavior while creeping the throttle up, but it was still present. So, tomorrow I will try other values/configurations of diode/resistors to see what I get. Koso has pretty much thrown the ball in my court by giving me a phone number to call for tech support. (even though I responded to just email me a solution.) Because of time difference, I can never call them after work because they're already closed. I hear/read a lot about using a 10K ohm resistor inline to eliminate the jumps. I found a 10k and will try that first thing tomorrow. Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted October 3, 2013 Member Contributer Share Posted October 3, 2013 Thanks again for updating us. I've had the same sort of response from Koso... I honestly think they just say they will contact their techs to make us happy. Who knows. One guy that fixed his jumpy tach said he played with all sorts of combos and using a floater resistor of higher value on the ground. http://www.kawiforums.com/ninja-250r/255417-koso-rx2n-issue-solved.html Link to comment Share on other sites More sharing options...
Guest Posted October 5, 2013 Share Posted October 5, 2013 Good news and bad...... Bad news, I tried using a 10K ohm resistor after the diode in my signal wire hookup. Still has some jumping, but seems to be "smoother" in the rise and fall of the tach needle. (??? might be my imagination) Still jumps around 2K and also seems to jump around a higher RPM, like 5-6K. Haven't been able to pin point it. Almost seems as though I may have a problem with the magnetic pickup that sends the signal to the ECU, which then sends the RPM pulse signal to the tach. I might be looking too far ahead into this. Only other thing I could try is to give the Koso unit it's own dedicated ground instead of using the factory ground wire, even though I cleaned and inspected all of them at the grounding point on the right side of the bike when I upgraded the charging system. Here's the yel/grn wire from the ECU. Diode and 22 ohm resistor Testing rig Good news, I fixed the speedometer problem! I noticed the other night how even at steady speed on the bike, the speedo would jump around 2mph up and down from a particular number. If I was going 25mph, the speedo would jump around from 23-27. This got me thinking about how the unit would act if it was not getting every one of the 6 magnets' signal to the speed sensor. Then I remembered that Andy and SEB mentioned how their Koso's instructions said to place magnets near the speed sensor around 2mm. The instructions for the Rx2 say to place them no more than 8mm. I had the sensor on the right side of the bike, using the addition "L" bracket, (none of the "S" brackets fit my bike) So, I relocated the sensor and magnets to the left fork and placed the sensor right around 2mm away from the magnets. I still used 1884mm for tire/wheel circumference and 6 pulses. YEAH, it works! Blame Koso for misprinting their instructions. http://www.kosonorthamerica.com/koso/shop/multi-functions-motorcycle_gauges/rx-2-speedometer-gp-style-4/ Click "Download Instructions", 2nd page. BTW, Koso did email me again. They want me to send them a copy of my wiring diagram. I think they're going to tell me what I already know. Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted October 5, 2013 Member Contributer Share Posted October 5, 2013 Glad to hear you fixed the speedometer issue. I would most definitely run a dedicated ground from the koso unit to a good ground on the frame or even the negative terminal on the battery. I originally had mine grounded to the harness and when I ran a dedicated ground my tach when from nearly inoperable to only glitchy in the 6-8k rpm range. Link to comment Share on other sites More sharing options...
Guest Posted October 6, 2013 Share Posted October 6, 2013 I originally had mine grounded to the harness and when I ran a dedicated ground my tach when from nearly inoperable to only glitchy in the 6-8k rpm range. Interesting about your harness ground. Must have had resistance in it, causing it to not work. But, you still have a tach problem around 6-8K? Have you tried any remedies? Link to comment Share on other sites More sharing options...
Guest Posted October 7, 2013 Share Posted October 7, 2013 FIXED!!!! :cheerleader: After more online research and contemplation (brain-racking), I believe it is fixed! I read more about "floating grounds" in a DC circuit and concluded that atkrank at the KawiForum had stumbled onto something. He used a similar setup to mine in order to fix his jumpy tachometer on his 250R and mentioned that he added a floating ground resistor in his setup. This got me thinking to try the same thing. Since his ECU and wiring on his 250R is similar (if not identical) to my EX250, it is not dissimilar to the VFR. So, I tested a 470 ohm resistor after my inline 150 ohm and diode, to see if it would eliminate the jumps in the tach. Viola! I could actually hold the throttle at the 2K range, while the tach was jumping all over the place, and touch the floater to the frame (ground) to watch the tach needle settle down to 2K. I did this for about 15 minutes just to make sure it was working, and that I wasn't hallucinating! Same as before, except I removed the 10K resistor and replaced with a 150. Then added the floater between the inline resistor and the gauge itself, then grounded the floater. Here's my crude schematic for all to enjoy... Thanks to apexandy, SEBSPEED and atkrank for their wisdom and inspiration. Everything now works on my Koso RX2 GP style meter! Hey apexandy, try that schematic on your VFR-SF and see if it eliminates your jumpy tach at the 6K range. Worth a shot. Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted October 7, 2013 Member Contributer Share Posted October 7, 2013 Well thank you good sir! I will most definitely try it out. Any tips on where to pick up the resistors and diode? High five!!! Link to comment Share on other sites More sharing options...
Guest Posted October 7, 2013 Share Posted October 7, 2013 Well thank you good sir! I will most definitely try it out. Any tips on where to pick up the resistors and diode? High five!!! Do you have Radio Shack in Canada? Otherwise, any local electronics store will have them. Good luck! Let me know if it works. Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted October 7, 2013 Member Contributer Share Posted October 7, 2013 Used to have Radio Shack... Circuit City bought them and now they are called "the source". I'll start there :) Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted January 6, 2014 Member Contributer Share Posted January 6, 2014 Bringing this thread back for a question… what are the wattage of the resistors used here? 150ohm 1/4watt and 470ohm 1/4watt? And is the diode important? I'm not sure what it does. Sorry about the electrical noob questions. Thanks! Link to comment Share on other sites More sharing options...
Member Contributer YoshiHNS Posted January 6, 2014 Member Contributer Share Posted January 6, 2014 Diodes are like one way streets for electricity. It probably is for keeping a voltage surge from coming to the board through the ground. Link to comment Share on other sites More sharing options...
Member Contributer apexandy Posted January 6, 2014 Member Contributer Share Posted January 6, 2014 Cool thanks! Any ideas on what wattage of resistors to use? I think the OP mentioned 1/4 watt for one of the resistors he tried initially, but didn't say on the final ones he used. Link to comment Share on other sites More sharing options...
Guest Posted January 8, 2014 Share Posted January 8, 2014 For the wattage I'm not sure but I think that it just defines how much power can the resistor survey, but it doesn't change its electrical properties. I purchased 5 watts for mines, but didn't tried it yet. In fact, we know that P(in Watts) = U (in volts) * I (in ampers) So what really defines our cricuit power is intensity. More power your resistor can absorb more stronger it will be. I prefered to take the safe choice with strong resistors, as i didn't check the circuit intensity ;) Link to comment Share on other sites More sharing options...
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