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-   -   low RPM stumble (http://www.chinariders.net/showthread.php?t=24144)

rjmorel 07-16-2019 02:59 PM

low RPM stumble
 
My 2015 RX3 17300 miles w/300cc kit seems to have developed a low RPM stumble when first warming up. After I get going and out on the road runs great. It's not real noticeable but when I'm just tooling around the parking lot in 1st gear like I'm trying to do low speed maneuvers it bucks a little. Get the RPMs up and runs good. Any ideas? I'm wondering if something electronic is carboned up or dirty sending bad voltage to the great whoever that makes all things go goodly?
How do you check for codes? turn key on /off 5x? Do you let the fuel pump complete its priming ? thanks rj

calvarez 07-16-2019 03:07 PM

Have you done the obvious such as cleaning the air filter and changing the spark plug?

NzBrakelathes 07-16-2019 10:56 PM

Stepper motor passage not clean super clean
Gently wire brush the nose of stepper
It’s not holding idle to throttle correctly so the transition from stepper to throttle isn’t right

rjmorel 07-17-2019 01:10 PM

Calvarez, not yet but I will, been busy and havnt checked it much since the Moab ride.
NBL, thanks I'll clean that also since I don't think it's ever been done.
rj

calvarez 07-17-2019 01:34 PM

How many miles are on the plug? On another forum, we're having a discussion about what a huge difference it makes to put in a new one on most bikes, and how the specified interval is often too long. And if you ride in dirt, that filter will clog up fast.

mckayprod 07-27-2019 08:29 PM

I'm watching this...mine won't hold idle speed until warmed up. Just started, too, right after an oil change. I thought that might be related, but I'm leaning toward just a coincidence right now.

calvarez 07-28-2019 02:40 AM

Same question... Have you done the obvious such as cleaning the air filter and changing the spark plug?

mckayprod 07-28-2019 07:41 PM

Good point; work in progress.

mckayprod 07-28-2019 10:58 PM

So, in the process of cleaning the air filter and checking the plug, I found the plug wire just hanging loose, disconnected. How I got home yesterday I'll never know, but somehow the rubber plug boot was too deep and springy and wouldn't allow the plug tip to stay connected to the wire. I know that rubber can swell when exposed to oil, and I've had a little oil seepage from the valve covers since my last valve adjustment. I cut off about 3/4 inch off the boot, seated the wire, cleaned & gapped the plug and cleaned and oiled the air filter. The bike now starts and idles without issue. New plug and wire are on order. I didn't mean to hijack your thread, RJ, but maybe this will help someone else.

rjmorel 07-31-2019 02:35 PM

mckayprod , Good on you. I'm going to go check my plug wire now. Mine just has a little stumble in 3rd going through town. I cleaned air cleaner, not very dirty and plug was replaced 3200 miles ago.

rjmorel 08-02-2019 01:42 PM

Quote:

Originally Posted by NzBrakelathes (Post 314267)
Stepper motor passage not clean super clean
Gently wire brush the nose of stepper
It’s not holding idle to throttle correctly so the transition from stepper to throttle isn’t right

So NZ, can you give me a quick instruction on where the stepper motor is and how to clean it good? I assume its on the throttle body but not sure where or how to get it out. Does gas tank need to come off? I have looked around and tried to find the info but keep running into dead ends. And well...………………………………….I'm lazy. thanks, rj

NzBrakelathes 08-03-2019 12:29 AM

Quote:

Originally Posted by rjmorel (Post 315359)
So NZ, can you give me a quick instruction on where the stepper motor is and how to clean it good? I assume its on the throttle body but not sure where or how to get it out. Does gas tank need to come off? I have looked around and tried to find the info but keep running into dead ends. And well...………………………………….I'm lazy. thanks, rj

take seats off, remove the 4 stainless screws holding plastics on and the 1 tank bolt remove tank n wire hoses (5 min job)
Directly below you will see the throttle body take it out remove black stepper motor clean clean clean the passage with Q tip brake clean etc and gently scrub the styepper nose. check throttle plate closes off correctly reassemble and reset ECU.

rjmorel 08-03-2019 01:03 PM

Thanks NZ, you the man, really enjoying the 300 kit I got from you. It's added that little oomph where it was needed power wise, rj

calvarez 08-03-2019 06:46 PM

Wait, 300cc kit and low RPM stumble...weren't there other posts about those being related? I'm not sure, just something in the back of my mind.

NzBrakelathes 08-03-2019 08:44 PM

Quote:

Originally Posted by calvarez (Post 315421)
Wait, 300cc kit and low RPM stumble...weren't there other posts about those being related? I'm not sure, just something in the back of my mind.

No not related - its common on any cc size.
The odd POP from exhaust maybe a little more common

rjmorel 08-04-2019 03:00 AM

Nz, to reset ecu, do I turn key on/off, on /off, on? Or will disconnecting the battery for 15 minutes reset the ECU when I reconnect battery? Thanks rj

NzBrakelathes 08-04-2019 07:43 AM

Quote:

Originally Posted by rjmorel (Post 315440)
Nz, to reset ecu, do I turn key on/off, on /off, on? Or will disconnecting the battery for 15 minutes reset the ECU when I reconnect battery? Thanks rj

On off 5 times in 5 or so seconds
Make sure you hear the pump prime so kill switch not in off position

rjmorel 08-05-2019 08:24 PM

NZ, I took out the stepper and the tip was pretty dirty as well as the cavity it sits in. cleaned out with Q tip and rag on the stepper tip. Put back together, reset ECU and it doesn't stumble anymore. Runs smooth from idle on up. Thanks so much for your tutelage.
Now can you explain when the stepper gets dirty, in my case 17,400 miles worth, it acts like it does? Is the tip some sort of sensor that when dirty doesn't sense like it should?
Is that exhaust grunge I cleaned out of stepper hole or just dirt from some wheres else, thanks, rj?

pyoungbl 08-06-2019 04:15 PM

rj, a stepper normally bleeds air into the engine as a way of controlling idle speed.

calvarez 08-07-2019 03:14 PM

Cleanable air filters are an awful thing. I've never seen throttle bodies and intakes as dirty as when people use K&N filters and junk like that. The filter on the RX3 is junky foam that you apply oil to in order to be cheap. Most people apply too much oil, and get oil all over the intake. Then the dirt that bypasses the filter sticks to it. Since oiled junk foam is a terrible filtering agent, lots of dirt gets in.

mckayprod 08-13-2019 08:21 PM

Two comments:
1.) The spark plug wire fix held up. I just finished a 2300 mile tour with zero issues. Thanks to all for the troubleshooting tips. This forum is great.
2.) Does anybody make a replacement, replaceable air filter for this bike? I'm one of those guys who goes overboard on the oil, and I don't care to clean that thing any more than I have to. I'd also like to avoid the stepper motor sensor tip cleaning described above. I'd prefer to just swap a filter element every 2-5k miles if I could. I'll check the Hi-Flo website first.

NzBrakelathes 08-14-2019 01:03 AM

Quote:

Originally Posted by mckayprod (Post 316060)
Two comments:
1.) The spark plug wire fix held up. I just finished a 2300 mile tour with zero issues. Thanks to all for the troubleshooting tips. This forum is great.
2.) Does anybody make a replacement, replaceable air filter for this bike? I'm one of those guys who goes overboard on the oil, and I don't care to clean that thing any more than I have to. I'd also like to avoid the stepper motor sensor tip cleaning described above. I'd prefer to just swap a filter element every 2-5k miles if I could. I'll check the Hi-Flo website first.

Just stock filter - if you look at the design how it fits I very much doubt theres any other way to add in a paper style

calvarez 08-14-2019 12:22 PM

I tried and failed to find a paper filter. Like Tako says, it just wouldn't fit.

Just go light on the oil! Look up a Youtube video from K&N or some reliable source like that. It takes only a tiny amount. I've owned my bottle of filter oil for nearly 20 years, it has 1/3 left.


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