Cold engine runs rough

[AstroStrat89]

This is actually my wife's Super Cub but hoping to get some suggestions since they share the same engine.

When starting the bike cold the engine seems like its going to stop. Give it a good twist of the throttle and it almost cuts the engine and even gets a bit of back-fire. It only take a minute or two before it seems to run just fine. My Trail runs like a champ when cold started so it seems something is not quite right. Have not found much addressing this issue with any of the Honda 125cc bikes yet. Thanks in advance.

 

[m in sc]

Oddly, Angies does too, noticed that just this morning. (21 super cub). figure the ecm is still learning as hers has about 70 miles on it. (shes had it 4 days). neither my grom (when it was stock), or the trail had that issue.

 

[AstroStrat89]

Oddly, Angies does too, noticed that just this morning. (21 super cub). figure the ecm is still learning as hers has about 70 miles on it. (shes had it 4 days). neither my grom (when it was stock), or the trail had that issue.

Thanks. We have 450 miles and have had it since April. Seem this has been slowly getting worse as time goes on. I've thought about maybe resetting the ECM as a troubleshooting step.

 

[m in sc]

interesting. I'll keep an eye on Angie's as well resetting ecm is a breeze too.

 

[AstroStrat89]

interesting. I'll keep an eye on Angie's as well resetting ecm is a breeze too.

Could you please share what you know about resetting the ECM?

 

[m in sc]

Supposedly on the Cub, you just disconnect the battery, then put the hot lead on the ground side terminal to reset. then reconnect the hot lead on the battery and its should be good to go. I have not tried this. ON the grom & Monkey, you jump 2 pins on a plug in the harness and there's a sequence with the key and throttle. This I have done, and it goes back into learn mode.

this is the procedure i found for the supercub:

Resetting the TPS on the Honda Super Cub

The TPS (throttle position sensor) is easy to reset on the Super Cub, and the result is noticeable. The factory setting is good for break in, and emissions regulations- but not as good as it could …

adamdanger.wordpress.com

 

[AZ7000']

Mine always pops in cold weather at altitude for the first mile or so…

 

[m in sc]

this is different. its like it idles low and is uneven, almost stalling, if we are experiencing the same thing.

 

[AstroStrat89]

this is different. its like it idles low and is uneven, almost stalling, if we are experiencing the same thing.

Yes, good description.

 

[AstroStrat89]

Resetting the ECM seemed to help but it also seemed to be not as bad even before. The troubleshooter in me says YMMV.