GT250 EFI 2013 Sluggish Starts.
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Bike Model = : GT250 D Spec 2013 EFI
I have been facing this issue for some time now. I have tried many things with no luck and have basically been living with this problem. In essence I need to continue pressing the starter button for at least 5secs before the engine picks up speed on both cylinders and then settles at idle.
Recently I am attempting again to understand what is happening at engine start. In essence how does the ECU know when to send a spark and inject fuel to each of the 2 cylinders.
There is only one pick up sensor in the magneto which basically sends out 23 cycles plus a space very revolution. This tells the ECU when the pistion has arrived at TDC only.
How does the Delphi ECU know which cylinder is at TDC and whether this is happening at the compression phase or the exhaust phase with just this one sensor?
Attached is a photo of the sensor signal(yellow) as well as the pulse sent to one of the coils by the ECU(green).
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I have had a few engines apart a few times, sometimes the pistons will be in different positions. I open the top valve covers to do clearance jobs , so i can either spin by hand to confirm the timings are correct , then i use a starter motor to battery to see if it will crank OK but ofcourse oil will shoot out!
Once the engine is completed and closed up, it did not matter where the piston was, the bike cranks within 2 seconds after the fuel pump stops priming. At some time ago, it took longer than 5 seconds to spin and start but it sounded weary.
So I removed the flywheel, and some some teeth of the sprag-clutch was gone , could this be related ?
Have you ever taken off your flywheel to inspect your starter-clutch system for abnormal wear / damage?
I recently worked on a customer’s 2017 bike GV250, it was a delphi. It was a stressful job! I changed a lot of things despite positive readings on the meter, the harness was clean as it could be , no wire oxidization yet (garage queen) , but i was shocked that in the end I replaced the stator unit & made sure the battery is 100% charged and brand new , voila it started within 2 seconds of the fuel pump priming. I didn’t really investigate too much as if “piston” position had any influence to how the ECU expects the piston to be.
However, everytime i press start (within a milli second) ==>i see sparks on the spark plug which tells me , the ECU had already been ready to fire up the coils as soon as i hold the clutch switch in. The suspicion in my mind right now is that it did not matter if the front was up, and rear was down or rear up and front down position of pistons , it always started in 2 seconds. Longer cranks in my past were a result of the fuel injection system needing a clean or fuel pump was underperforming. I did not keep DELPHi systems for long , but i always had Daewoo & Sentecs bikes to work on. Sometimes my customers ask me to just convert the machines to “carby” (expensive investment but less maintenance in the long run however the DELPHi system is not too bad, and is more “instant response” with throttle which is good)
As i get more information , I will share when i can. I don’t think i’ve heard too many people discuss piston position vs cranking time for ECU. I have to keep in mind both cylinders are connected to the same crank anyway! Everytime the bike is switched off (during a crash, or normal riding to stop or rider activates killswitch, the pistons don’t always return to the same position as they did before , a bike could be switched off mid cycle. )
// Meditation doesn't mean you have to sit still....
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@MARCEL, Thank you for your comments. Although my bike is a 2013 bike, due to various problems I have had with it, it has only about 26000km on the clock. Since your suggestion to inspect the sprag-clutch entails dismantling the whole engine I will leave this as a last resort. I have done most of the other things you have suggested including removing the cylinder heads and decarbonising and rebedding the valves, replaced the coils, plugs and ht cables. I was even lucky to purchase, at a very low price, a second hand ECU which was never used due his bike getting stolen and changing this had no effect either. I have changed the fuel filter inside the tank, checked the ISC, cleaned the injectors all to no avail.
Since besides the sluggish starting I am still facing issues with the engine beginning to miss after about 15mins working and eventually it stalls completely, that is why I am turning my attention to the operation of the pickup coil.
So far I have found very skimpy information on the internet re answers to the questions I posted earlier. There are a couple of sites involved in the building of ECU’s for racing motor bikes which discuss this vaguely.
Some proposals include the ECU sending a pulse on BOTH plugs at startup and then monitoring the peak to peak timing of the pick up coil pulses shown in yellow above. The theory being that at the point that the peak to peak time is longest that particular cylinder is in the compression stroke phase. This sounds quite tricky to me. Others seem to somehow monitor the MAP sensor but this method seems even more vague to me.
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You could monitor the A/F ratio on the exhaust and also use some kind of heat gun to measure cylinder temperature so you know which one is still cold ? as you said it stalls in 15mins of working ? =
Measure that temp sensor on the front cylinder cold and hot values vs the manual figures.
Removing the flywheel does not require a full dismantle of the engine. Just the flywheel stator cover off, then extract the flywheel out , that’s it. You should be able to see if the sprag system is worn down (since it is 26,000 km , so it could be worth a look!)
// Meditation doesn't mean you have to sit still....
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