15 RT rough idle

[derache123]

Hey all,

 

My 15 RT started experiencing some rough idling recently. The engine sounds like it's stumbling a bit while idling and seems to stall more easily than it should when taking off from a stop (have to be extra gentle while letting out the clutch). Everything feels completely normal above idle though - I've been riding it and when it's not at a stoplight it feels great. It's just at idle when it sounds and feels rough.

 

I tried resetting the idle mixture, throttle valve, and throttle twistgrip calibrations via GS-911 and it doesn't seem to have made much of a difference. Was thinking of changing the spark plugs next, but the spark plugs are fairly new (less than 10k miles old, installed last year) so not sure if that makes sense (plus it only feels weird at idle, not at any other point in the rev range).

 

It seems to have started after I dropped the bike recently (on both sides...) and both cylinder heads scraped the ground for a bit, not sure if that could've damaged something in the heads? Any pointers would be super helpful.

 

Thanks

[dirtrider]

23 minutes ago, derache123 said:

Hey all,

 

My 15 RT started experiencing some rough idling recently. The engine sounds like it's stumbling a bit while idling and seems to stall more easily than it should when taking off from a stop (have to be extra gentle while letting out the clutch). Everything feels completely normal above idle though - I've been riding it and when it's not at a stoplight it feels great. It's just at idle when it sounds and feels rough.

 

I tried resetting the idle mixture, throttle valve, and throttle twistgrip calibrations via GS-911 and it doesn't seem to have made much of a difference. Was thinking of changing the spark plugs next, but the spark plugs are fairly new (less than 10k miles old, installed last year) so not sure if that makes sense (plus it only feels weird at idle, not at any other point in the rev range).

 

It seems to have started after I dropped the bike recently (on both sides...) and both cylinder heads scraped the ground for a bit, not sure if that could've damaged something in the heads? Any pointers would be super helpful.

 

Thanks

Afternoon derache123

 

You might at least look at the spark plugs, sometimes dropping the motorcycle can allow oil to get into the cylinders so possibly you have some remaining oil residue on the spark plugs.

 

Also dropping the motorcycle can allow a little water that might be in lower front of the fuel tank to mix with the fuel supply (not common but can happen). Ride as much fuel out of the tank as is safe then re-fill with fresh gasoline. 

 

If you have a GS-911 then do a data trap to see  what o2 sensor output & the hot engine idle fueling looks like, possibly some oil that got into a cylinder on the tip-over that is effecting an o2 sensor. (this will probably burn off after a long high speed run).

 

Was there any deep damage to the valve covers?  If they didn't get displaced or caved in then probably nothing inside was damaged. 

 

 

 

 

 

 

 

 

[derache123]

Thanks for the suggestions, much appreciated. I will take a look at the spark plugs. I'm guessing if I see any oil residue then I'll want new plugs?

 

16 minutes ago, dirtrider said:

If you have a GS-911 then do a data trap to see  what o2 sensor output & the hot engine idle fueling looks like, possibly some oil that got into a cylinder on the tip-over that is effecting an o2 sensor. (this will probably burn off after a long high speed run).

Will take a look at this as well, but I have already done a couple of long-ish highway rides (~100 miles) since I dropped it so any oil in the cylinder probably would've burned off by now?

 

18 minutes ago, dirtrider said:

Was there any deep damage to the valve covers?  If they didn't get displaced or caved in then probably nothing inside was damaged. 

Nope, no significant that I can see, just scrape marks.

[derache123]

EDIT: removed accidental double post

Edited April 26 by derache123
double post

[JCtx]

I'd check that your exhaust valve is operating properly. My brand new '20 R was stumbling when cold, and it was that stupid valve. I removed the servo (plugged a 'servo buddy' in its place), along with the cables, and the valve is fully open all the time now (default setting), and problem solved. No cold stumble anymore, no low rpm choking, and engine sounds nicer now. If your bike wasn't having that behavior before the drops, it might not be your issue, but a possible culprit, so I'd check it out. Good luck.

[Camhead64]

Crappy gas?