dye29 Posted October 30, 2010 Report Share Posted October 30, 2010 (edited) hy i have just got a small tachometer to test the rpm on 4rt it says connect to ht leads but not sure exacly where to connect, just figured that out now the only prob setting the tach up it says spark revolutions what is this i dont have a clue Edited October 30, 2010 by dye29 Quote Link to comment Share on other sites More sharing options...
big john Posted October 30, 2010 Report Share Posted October 30, 2010 hy i have just got a small tachometer to test the rpm on 4rt it says connect to ht leads but not sure exacly where to connect, just figured that out now the only prob setting the tach up it says spark revolutions what is this i dont have a clue Start bike and let it idle, I presume you are either to hold the tachometer close to the HT lead or have wrapped a small wire around the HT lead. The RPM for a 4RT is 1800 approximately. If your tach is showing around about that figure (1800) the tach, it is set correctly... if it shows your bike idling at say 900 rpm or much higher or lower (3600 rpm), then you have to adjust the tach to another setting as it is set incorrectly. Note: some tach's don't pick up any reading at all, because the 4RT is fuel injected. Big John Quote Link to comment Share on other sites More sharing options...
dye29 Posted October 30, 2010 Author Report Share Posted October 30, 2010 Start bike and let it idle, I presume you are either to hold the tachometer close to the HT lead or have wrapped a small wire around the HT lead. The RPM for a 4RT is 1800 approximately. If your tach is showing around about that figure (1800) the tach, it is set correctly... if it shows your bike idling at say 900 rpm or much higher or lower (3600 rpm), then you have to adjust the tach to another setting as it is set incorrectly. Note: some tach's don't pick up any reading at all, because the 4RT is fuel injected. Big John hy yes just wrap wire round ht leads but i have to set the tachometer up it has 4 settings 1 for a full revalation 1 for 2 sparks per revalation and others wich one do i need for a 4stroke 4rt regards ste Quote Link to comment Share on other sites More sharing options...
big john Posted October 31, 2010 Report Share Posted October 31, 2010 hy yes just wrap wire round ht leads but i have to set the tachometer up it has 4 settings 1 for a full revalation 1 for 2 sparks per revalation and others wich one do i need for a 4stroke 4rt regards ste see what reading you get for 1 revolution and if it reads around 1800 rpm on idle or thereabouts that is the setting you need, if it reads half that or double, then you have the wrong setting! Big John Quote Link to comment Share on other sites More sharing options...
jimmyl Posted October 31, 2010 Report Share Posted October 31, 2010 would suggest 1 spark for 2 revolutions as its a single cyl 4 stroke (unless it fires on induction as well as power stroke but wouldn't of thought so). Quote Link to comment Share on other sites More sharing options...
gii Posted October 31, 2010 Report Share Posted October 31, 2010 Yep, I had to set mine to 1 spark every 2 revolutions or every 720 Quote Link to comment Share on other sites More sharing options...
jimmyl Posted October 31, 2010 Report Share Posted October 31, 2010 It must know what the cam is doing as wouldn't inject fuel when on power stroke but can't recall any sensors on top end of motor either. Quote Link to comment Share on other sites More sharing options...
gii Posted November 1, 2010 Report Share Posted November 1, 2010 It must know what the cam is doing as wouldn't inject fuel when on power stroke but can't recall any sensors on top end of motor either. Umm, maybe, but I don't think that's the case, obviously diesels do but petrol motors don't have to unless they're direct injecion, I think on the 4RT the injector just sprays fuel into the inlet tract at the rate governed by the ecu map for the operating conditions. Quote Link to comment Share on other sites More sharing options...
dye29 Posted November 1, 2010 Author Report Share Posted November 1, 2010 Umm, maybe, but I don't think that's the case, obviously diesels do but petrol motors don't have to unless they're direct injecion, I think on the 4RT the injector just sprays fuel into the inlet tract at the rate governed by the ecu map for the operating conditions. hy i think iv cracked it its one full revalation thanksw guys Quote Link to comment Share on other sites More sharing options...
jimmyl Posted November 1, 2010 Report Share Posted November 1, 2010 Umm, maybe, but I don't think that's the case, obviously diesels do but petrol motors don't have to unless they're direct injecion, I think on the 4RT the injector just sprays fuel into the inlet tract at the rate governed by the ecu map for the operating conditions. Not wanting to hijack the thread but my technical intrigue makes me think that the japs would not have fuel pooling in the inlet manifold when on the power stroke. Quote Link to comment Share on other sites More sharing options...
gii Posted November 2, 2010 Report Share Posted November 2, 2010 Interesting, As I said, I couldn't see why it would be anything different but I definitely had to set my tinytach to 720 Quote Link to comment Share on other sites More sharing options...
jimmyl Posted November 2, 2010 Report Share Posted November 2, 2010 Yes having done the maths after posting theres not much delay even at tick over. The air flow is measured in the throttle body and combined with rpm and throttle position the injector just supplies accordingly. Not sure if it pulses or continual jet. Cant see any way the ignition will know what the cam is doing so maybe does spark every stroke. Quote Link to comment Share on other sites More sharing options...
stork955 Posted November 2, 2010 Report Share Posted November 2, 2010 Gday, it would fire every revolution. Its called "wasted spark" and its very common. The only way to have it only fire once per cycle is to use a sensor on the cam as it rotates only once per cycle. Often tacho's will ignore the second spark because its voltage is very low while there is no "load" on the spark plug from compression. The injector pulses on and off continually, its the length of the pulse that determines how much fuel is injected. Each pulse lasts for a few milliseconds according to demand. ("on" Longer for more fuel, "off" longer for less fuel etc.)The system on these bikes is not overly sophisticated as far as EFI goes. Cheers, Stork Quote Link to comment Share on other sites More sharing options...
dye29 Posted November 2, 2010 Author Report Share Posted November 2, 2010 Gday, it would fire every revolution. Its called "wasted spark" and its very common. The only way to have it only fire once per cycle is to use a sensor on the cam as it rotates only once per cycle. Often tacho's will ignore the second spark because its voltage is very low while there is no "load" on the spark plug from compression. The injector pulses on and off continually, its the length of the pulse that determines how much fuel is injected. Each pulse lasts for a few milliseconds according to demand. ("on" Longer for more fuel, "off" longer for less fuel etc.)The system on these bikes is not overly sophisticated as far as EFI goes. Cheers, Stork thanks stork any ideas on why mine takes a while to start Quote Link to comment Share on other sites More sharing options...
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