wonder if it could be jumping between open & closed loops...

Don't know why I didn't connect these posts earlier.

Bobrx3 and Katflap, meet Riceburner. Rice, meet the tech folks.

http://www.chinariders.net/showpost....59&postcount=1

Carb vs. FI, same rpm range. Grab beers and engage.

The carb issues sound different. Looks like the carb setup was running rich in a particular rpm range, which is something cured by changing the needle profile and/or the needle height. On an FI bike that's the equivalent of changing the fueling map stored in the EMU.

I don't have an EGA, but the O2sensor should tell me if the bike is running rich or lean and the O2 sensor tells me things are OK. Being a narrowband sensor it's output is either "rich" or "lean" and it bounces between the two (in closed loop) as it would be expected to.

Surging is, I think, something of a common problem with small capacity, single or twin FI bikes. They are never in a steady state like a carburetted bike and the engine doesn't have enough inertia to smooth things out. They are constantly responding to inputs from the MAP, MAT, TPS and O2 sensors, changing the injector opening times to correspond with the fuel map and the sensor input corrections. My DL650 had similar issues. Here's a "tale of woe" thread about surging on the DL650 - http://www.vstrom.info/Smf/index.php/topic,5935.0.html - I think the eventual conclusion was something like "they all do that to some extent", but no definitive diagnostic conclusion. Neither the dealer nor a custom tuner was able to properly fix it. The RX3 may be the same. I'd love to ride another RX3 to see if it's my bike or it's just me that's overly sensitive to the issue. However I doubt there's another RX3 within 500 miles of me. There's certainly not another one anywhere in Maine unless someone has ridden up here on vacation! I think there's one in NY state somewhere. There's also a guy in NH who is looking to get one in the fall. That's one problem with the RX3. If you think have a problem you can't just find another bike to compare it to unless you live near CSC...or you buy two of them.

On light throttle I'm pretty sure it stays in closed loop. The diagnostic readout has the info and I'll take a look. It's not slack in the throttle cable (when testing in neutral at around 3000-4000rpm) because I raise the rpm with the bike in neutral by holding the throttle open with a 1mm shim at the throttle body. The diagnostic readout shows a constant TPS signal. On the road there could be a component due to not being able to keep a constant throttle opening as well as chain slack and cush drive movement, but the fact that the rpm fluctuates in neutral when I know the throttle is fixed and there's no chain or cush drive involvement makes me think it's not 100% a mechanical issue.

Thanks for all the suggestions. I haven't given up since the bike is perfectly rideable. It just bucks and surges a little at low speed in town and surges a little at a constant speed on neutral throttle when I'm trying to hold it at the speed limit in 35-45mph zones. It's annoying but I can live with it if I have to - as long as it doesn't get worse.

I don't think there's any way to see the actual spark advance. That's an output from the EMU, not an input to it, so all you can see is the calculated output signal. You can see the spark dwell time and nothing looks unusual there.

The troubling thing is that I don't remember it doing this when I first got the bike and I was doing the break-in over the first few hundred miles. I con't be sure if it didn't do it or if I just didn't notice it. I've only got around 600 miles on it now, so it's not a matter of something wearing. It was doing it both before and after I checked the valves at 500 miles, so it's not a valve adjustment issue and it's not something I disturbed pulling the tank to get at the valves.

I've done a little research,

It would seem that an ECU is capable of adjusting the injector pulse width to accommodate varying battery voltages.
The idea being that the lower the system voltage the longer it takes for the injector to open, thus requiring a larger pulse width to deliver the same amount of fuel.

I ran my test soon after I had started my bike.

I wonder if then at idle my system voltage was running relatively low so requiring quite a large pulse width.
Then when brought up to 4000rpm the magneto was working better, bringing the system voltage higher so enabling the pulse width to be smaller even though it was actually injecting more fuel.

This is the only possible answer I've been able to find so far :hmm:

( Apparently it takes approx. 1 m/s for an injector just to open and close)

In Turkey many of Rx3 owners were complaining about unstable rpms and stopping problems.The company Mondial has tried to solve this problem .Now they are changing the O2 Sensors who has these problems in their bike.Now everyone is happy .
I didn't have any stopping problem but sometimes my bike has unstable rpms too.
Today i disconnect the O2 sensor socket and rode my bike.Allday long i had really good time with my bike☺.U should try some day, There is a great power differance. Motorbike is like a monster.Everytime u open the throttle u feel a more agressive bike.There was no unstable rpm anymore.it is now working like a clock.i don't think my O2 sensor has a problem but all rx3 owners who changed their O2 sensor is telling the same thing ,no unstable rpms ,no stopping anymore .I mean without the original O2 sensor and with new bosch sensor ,bike is working verywell. İ guess a better sensor will be a good idea.

Old thread, I know, but it addresses my recent experience. I was out riding last week, about 75 miles from home, when I noticed that the bike acted like it was going to die (like it was out of fuel or something). I was running about 50 mph in 5th gear, and starting up a slight grade, so I applied throttle to maintain speed. When I hit the throttle, it "bucked" for lack of a better term-sputtered and then kicked back in. It continued to do this until I got back into cell phone range. The "check engine" light came on and went off intermittently, as well.

When I got to cell phone range, I called Gerry at CSC and he walked me through reading the error code. The code was 0132, which indicates a fault with the O2 sensor. Gerry had me check the connection to make sure it was good, and it was. I rode home, but not easily-I felt like I was killing my poor bike! It would accelerate OK if I was gentle with the throttle, but as soon as I got near 6000 RPMs, it would start "bucking" again. Made it home and parked, and Gerry's sending a new O2 sensor. Hopefully that corrects the issue!

Thank you for letting us know about the O2 sensor problems in Turkey. :)

Thanks for letting us know about the problem. If anything serious is wrong with the EFI system, the ECU will generate a DTC (diagnostic trouble code). :) As usual, Gerry and the rest of the gentlemen at CSC provided excellent customer service. :tup: