04 Cr250r Rc Valve Problem

[04cr250r]

I have an 04 HONDA CR250R with an RC valve that intermittantly when you go to accelerate does not open. I have cleaned and ajusted the valve. I have replaced the actuator. I have replaced the ECM. I have replaced the voltage regulator. Nothing has made any difference. It is hard to diagnose becouse it is very intermittant, but I have wired a test light into the actuator a couple different ways and taped to the cross bar pad. The ECM reverses the power and ground to the actuator to close it as well as open it and it apears as though when the valve does not open that the ECM is actually trying to pull it in the closed direction instead of open. :bang: Just hoping someone has seen this or has some idea what could cause it.

Thanks

 

[DieselTech]

I have the factory service manual if that helps. BTW, have you checked the wiring for any intermittent open circuit conditions while pulling/bending/wiggling the wiring? Alot of intermittent conditions are caused by wiring problems.

 

[04cr250r]

Yes I still think is possible I could be missing an intermittent wiring concern, but I have had the harness off the bike, used and ohm meter to make sure no wires are shorted together and used a light and a car battery to load test each circuit. When you first start the bike it pulls the valve completely closed and then opens slightly. With the way the cables are set up I think it does this to learn the closed position each time you start the bike. I think it's possible something could be causing it to loose it's memory so it has to pull the valve closed again to relearn the closed position. Does the manual give any description of what inputs and what parameters the ECM is using to determine what position it wants the valve in? I see you are a Diesel Tech. I am a GM Certified World Class Tech. You would think I would be able to fix this thing but so far not so much. Thank you very much for your input.

 

[_JOE_]

Have you checked all the grounds for corrosion?

 

[DieselTech]

Well, the inputs/outputs to the ECU are:

On the 8-pin connector:
Servo Position Sensor GND (-) - Blue/Grn wire
Servo Position Sensor Signal (RC/V) - Lt Grn wire
Servo Position Sensor PWR (+) - Yel/Red wire
Battery + is the Red wire, goes to the regulator (no battery!)
Ign GND, which goes to the coil and voltage reg, as well a frame gnd, is the Grn wire
Note: the engine stop switch is spliced into the Grn wire also (Blk wire)
Servo Motor PWR (+) - Wht/Blk wire
Servo Motor GND (-) - Wht/Grn wire

On the 4-pin connector:
Eng stop switch - Blk/Wht wire
AC - Wht wire, goes to alternator (stator) as well as regulator
Ign pulse generator GND - Grn/Wht wire
Ign pulse generator POS - Blu/Yel wire

If you check the Servo sensor resistance @ approx. 70 degrees F (Yel/Red & Blu/Grn wires @ 8-pin connector) it should be 3.5 - 6.5kohm. That's really the extent of the testing in the book. There's no info regarding the ECU operation or control of the RC valve, other than the initial operation ("The RC valve operates from fully closed to fully opened and returns to fully closed position in the initial stage after engine starts"). That's it.

Are you sure it's an RC valve issue? What exactly is the "driveability complaint"?

Oh, and keep in mind that even with your meter set to ohms, you can still have continuity on a bad wire so long as there's still at least 1 strand in the wire that's not broken - even if the rest are - but when current is applied, the resistance will go up and a voltage drop will occur, which can create problems. You can load each wire with a battery and your test light, then wiggle test the harness - if the test light flickers or gets dim, you've got a problem. You can also have your meter connected at both ends and set on the volts scale while doing this - you are now testing voltage drop on the circuit - and it should be very close to zero, any more than about .2v is a problem. If you want me to scan the pages in the manual & email them, I can. HTH

 

[04cr250r]

There is only one ground on the harness and it is clean and
tight. I load tested the circuits becouse I know like you said it only takes one strand to ohm good. But I did not do a voltage drop test when I was testing with the light. That is a very good idea.
What the bike does is intermittently when you go to accelerate the motor does not stumble at all but the tone of the exhaust is different and it has no power. With the cables off and the valve shut it acts exactly the same. With the power valve wedged wide open the problem never happens. I have even raced it that way a couple times. I think at this point it must either be a problem with the harness that I have missed or a voltage concern created by the alternator.

Thanks for your input.

 

[DieselTech]

I doubt that this is it, but were the cables adjusted properly?

And for the wiring, don't forget to wiggle/bend the harness to check for intermittents. :cool: