Took my 08 nightster out for some twisties today and in order to utilize the engine brake and to control the speed without applying the brakes, the engine was revving higher than normal.

During the ride, I noticed that my check engine light came on and stayed on for a couple of miles until I reach a stop sign.

As I slowed down for the intersection, I down shifted all the way to 1st gear with my clutch fully depressed and even though when I came to a complete stop, the engine was revving very high for about 5 seconds until it came back down to idle speed (this happens to me all the time) and as soon as the idle RPM was reached, the check engine light went off.

1. Why does the engine keep revving without any throttle in some cases when you come to a stop? Is this a fuel injection thing? Does anyone else experience this?

2. Should I get the bike checked out since the check engine light came on? Once it turned off, it stayed off until I got home which was about 40 miles and I was in 5th gear most of the time with no down shifting.

Thanks in advance for the input!

 

Have you changed bars? Sounds like possibly one of the throttle cables catching or a return spring issue. Though the "check engine" light is a concern. I would run through all the cables and springs, if that doesn't fix it, have it checked.

 

No..still using stock bars. I don't think the engine rev is due to a mechanical issue with the throttle but it seems like a function of the engine itself.

I think you can replicate this by down shifting at some significant speed as you're approaching an intersection. I always thought that the engine kept revving as a safety measure since you're still rolling so that if you accidentally re-engage the clutch, the engine can catch up rather than going from an idle rpm to however high it needs to go to sync up with the wheel rotation. It kind of seems similar to my manual transmission car where it's hard to put into a low gear when you're going at higher speeds even when the clutch is fully depressed.

That was just my guess though and I wanted to see if others experience it too when they come to a stop sometimes. It's not all the time but I'd say it happens often.

 

You might have a slight "high rev" as the engine drops to it's idle speed, but nothing as significant as you talk about. If your cables aren't adjusted right, or they are hanging up in the guides, or your return springs are stretching then you would get a "high rev" issue. But the "check engine" light is a lot more concerning.

 

It's not supposed to do that.
There might be a problem with your throttle position sensor. Check the trouble codes or take it to a dealer and let them check it out.