Hi guys, I have a Kawasaki KX250F 4 Stroke single fuel injected motocross bike that has a very intermittent problem. It sometimes hard to start and occasionally will miss thru out the rev range but mostly when wide open in the higher rev ranges. I would appreciate some feedback on waveforms. I have uploaded to the cloud under James Hunt KX250F. It uses a upstream injector in the airbox and a downstream in the throttle body. The downstream injector fires all the time, the other in the higher rev range. I believe it i looking like a faulty ECU but would certainly appreciate some thoughts from the experts.

James H wrote on May 18^th, 2017 at 3:58pm:

I would appreciate some feedback on waveforms.

Just some observations James

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Mick wrote on May 18^th, 2017 at 5:44pm:

James H wrote on May 18th, 2017 at 3:58pm: I would appreciate some feedback on waveforms. Just some observations James

Because of this have you checked all your powers and ground when this happens?

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James, as per phone this morning as I could not get into drop site, glitched on this end, will talk to Tom Today or Brian, most likely my bad, always it.

Noting what Mick stated, what we see as a double strike may not be, as the time frame one full strike, My guess about 4 MS as I can't get the file, is not a double strike but an attemp by the ECM to make a 4MS strike, lost driver for what ever reason then got it again but never able to implemint opeing thus not seeing any drop in fuel pressure typical  (red channel) of all one strike events. I.E. Mick illuded too wiring too and from, will tell over time.  Don't know how the TB works, is it a solinid or what, can it stick, have no idea, but as stated my gut feel is ECM loosing drive for what ever reason.

We stated not knowing strategy here and maker will not give you any,   we have to proceed with known good, if we had one.

I asked how is this ECM operated? We have no 02 sensors, so fuel must be dictated as we spoke from MAP (it has) TPS
(it has) which is my guess and possibly temp sensor. Would be interested over time on a good running unit what are these like, do they give you any feed back as we would say fuel trims.

I don't know what fuel trims you have on scanner, maybe none. 

Would be interesting to see how the time base on the blue votage, and green amps (both TB part of system) change depending on TPS, MAP and the like.

For want of a better definiton I view the TB part of this as like an idle and pilot jet, working all the time or up too about 1/3 throttle, then when we get after it the main jet (carburated) will integrate with pilot and idle, and possibly the pulse width on the TB part will increase, and also maybe the time base on the port injector will also increase, all this conjecture at this time. 

As for Mick, far more literate than  I on cars, we are shooting in the dark, but over time will develop a basis for how the bikes work, again The PICO is the tool.

For giggles in the learning process, can you some time get a screen capture of scanner info for us, would give us an idea of what we get and don't. As stated would always be curious of baro which will dictate fuel, ect. just a base point before we hook up to Pico.  If the barro was for instance 22, thinking it was in Denver colorado, you are going to have a shortage of fuel, just a thought.

Larry

An update for those who are interested as well as many thanks to Stitch, Spence and Mick for helping me look in the right direction.  It turns out is was a very intermittent hard to find wiring problem on the ground side of the TPS.

James H wrote on Jun 9^th, 2017 at 5:55am:

An update for those who are interested as well as many thanks to Stitch, Spence and Mick for helping me look in the right direction.  It turns out is was a very intermittent hard to find wiring problem on the ground side of the TPS.

[smiley=thumbsup.gif]  That put the computer into asynchronization mode(in other words for the old carburetor guys an accel pump) with the fuel injectors. Kinda what we were talking about on the phone.   8-)

Way to go with sticking with it.

Any after captures?

Here is the last capture I did after the fix.

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James H wrote on Jun 12^th, 2017 at 12:38pm:

Here is the last capture I did after the fix.

Sweet! Do you still have the bike there?

Hi Spence, no unfortunately. It was a real rush to get it out of here once we found the problem. The customer was getting pretty impatient at this point.

James H wrote on Jun 13^th, 2017 at 7:06am:

Hi Spence, no unfortunately. It was a real rush to get it out of here once we found the problem. The customer was getting pretty impatient at this point.

No worries mate. If you feel like playing and want to get an idea of what I look at give another bike a try with a voltage lead on both sides of the injector and an amp clamp on the supply for a total of three channels being used.

Have an awesome day and thanks for the reply!

Spence   8-)

I will be sure to try that at my next opportunity.. Thanks!

James H wrote on Jun 13^th, 2017 at 7:06am:

The customer was getting pretty impatient at this point.

James, impatient, should send him too the dealer and after a new ECM, both injectors ects, then he can be impatient and broke as I see it.  LOL.