CB650F High idling

[bram2202]

Hallo.

I have a problem with my CB650f (2015 abs) which seems I just cannot solve.
At the end of the season I noticed a couple of things, of which I do not know if they are connected

1. After a drive with some fast acceleration i noticed a rotten egg smell coming from the bike / exhaust.
This is probably the catalytic converter converting stuff into sulfur.
But in the couple of years I had the bike I never noticed this before.

2. The idle is high, on startup but also when driving.
on startup its about 2.000+rpm, and when flicking the gas it will even go to a idle of 3.500rpm.
Even after a drive it will idle around the 2.000+rpm.

The annoying thing is that while driving it sometimes idles around the 3.500rpm making engaging the clutch unpredictable.

This winter I did some maintenance, replacing filters, oil and the spark plugs.
And found that some of the vacuum tubes to the MAP sensor where split, so I replaced these, thinking I found the cause of the idle issue.
Some other things I checked/done:
- Cleaned the IACV.
- The clutch leaver switch works correctly
- Throttle grip/cable free play is in spec, and body closes as normal.

But the problem is still here!
I poked around the tubes in search of other split tubes, but all seems fine.
Last night is pulled the MAP sensor from its mount to see what would happen:
When seated it idles around the 2.000rpm mark, when pulled from its mount it drops to below its spec.
After reseating the sensor it goes back to 2.000rpm


If read some posts on this forum from uses with the a somewhat similar issue,
But found nothing that helped.


Does anyone have any idea what this could be.
Or how to diagnose this?

Thanks!

 

[Cláudio Nogueira]

Hello.

First possible causes that come to my mind:

Issue 1- Mine does it to. Never bother about it. I consider it normal, as my bike is fine. But always has that funny smell after a hard ride.

Issue 2 - Seems your ECU is considering the engine to be cold, like when it starts, so, probably making a wrong idle and timing setup. Have you checked if coolant temperatura sensor is connected and the ECU receiving a plausible information? Other way I think that if it was open circuited, you would probably be getting a ECL. What about other sensors that might support ECU in idle / timing management? Maybe it worth checking if they are delivering a plausible information. Easier said than done, I know.

Just a suggestion.

 

[bram2202]

Hi,

I don't know the inner workings of the ECU and if the Temp sensor has any effect on the idling speed,
but its a reasonably easy thing to check.
So i will check that sensor and some others while I'm at it.

Maybe a faulty sensor or a bad connection.


Thanks!

 

[Cláudio Nogueira]

"I don't know ... and if the Temp sensor has any effect on the idling speed,"

It has. Coolant temperature is one of the primary contributor for the algorithm. How do you imagine the "ECU knows" the engine is cold and need a specific timing setup and idle speed, to start and work OK?
The best way it would be to connect a OBD2 device and check for a few basic sensor readings, to see if they are delivering plausible readings.
Looks complicated but today, you can buy a OBD2 cable and a BT adapter. With free android software you can access to many things.

 

[bram2202]

Makes sense.

Buying a 4-pin to OBD2 cable was the first thing i did.
After connecting a BT adapter the MIL show an `Serial communication malfunction` error.
After some digging on forums i found out that the 2015 model has no ODB2, But correct me if i'm wrong.
Either i did something wrong, or the bike really doesn't have ODB2.

 

[bram2202]

I was able to test the temp sensor, and it worked withing specification, also tested the air temp sensor, also within spec.
While putting it all back together is cleaned every connector i could find.

I shot two videos, one of a cold start, and one after a ride;


Cold, starting low-ish in revs, but after a small flick it goes to almost 3.000rpm.


And the one after a rind, all was warmed up, but still around 2.000rpm

 

[Brammers]

Going out on a limb here... Have you checked the TP sensor at all?

There is a reset/calibration procedure (I've seen it posted here before). Could be worth a try.

Service manual also says to check the air filter and airbox etc. for a leak... That could be throwing the MAP sensor readings off and would act like a split hose.

J

 

[Dan1001]

also going out in a limb. Have you checked the throttle cable adjustment? I've had a almost the same issue on another bike of mine. There was no free play on the throttle, the adjustment had wound its self out.

 

[miweber929]

My opinion is you’ve got an air leak or something in the throttle cable is hanging up after watching the videos. I’d also be looking at a TPS reset if it were my bike.

I’ll ask the same questions I always do:

1. Has it always done this or did it suddenly start? Did it gradually gotten worse? Hanging idle, not smell, I’m going to ignore that for now.
2. What mods or maint had you done leading up to this, no matter how insignificant it may seem?
3. Anything done to the exhaust? I’m wondering if your cat is getting plugged which is affecting the back pressure/ability for the bike to breathe. Can’t remember if there is an exhaust valve on this bike or not but if so is it functioning?
4. How many miles, what’s the maint like, up to date?

Let’s start here.

 

[Cláudio Nogueira]

Have double-checked all the tibinhs from

also going out in a limb. Have you checked the throttle cable adjustment? I've had a almost the same issue on another bike of mine. There was no free play on the throttle, the adjustment had wound its self out.

I bet my money on this one
Things tend to be simpler than we expect them to be.
Yea, worth checking the accelerator play.

 

[bram2202]

I started with the reset/calibration of the TP sensor.
First as the manual indicated, jumping the Temp sensor, but did not work, and after some Google-ing i found out that this often does not work.
I found a post on this form which indicated another way: https://650f.bike/threads/engine-light.5265/post-52881
Not sure if it did anything, but this didn't help.

After that i checked the play on the throttle cables, and these where fine, the throttle fully closed.
These was enough play on both cables

Going out on a limb here... Have you checked the TP sensor at all?

There is a reset/calibration procedure (I've seen it posted here before). Could be worth a try.

Service manual also says to check the air filter and airbox etc. for a leak... That could be throwing the MAP sensor readings off and would act like a split hose.

J

I checked everything again for leaks, but could not fine any major ones.
About the throwing off the MAP sensor, if i remove the sensor from its mount (not disconnecting) while running, the RPM falls to 500rpm. Far to low.
If there where a major leak, would it not act in the same way?

My opinion is you’ve got an air leak or something in the throttle cable is hanging up after watching the videos. I’d also be looking at a TPS reset if it were my bike.

I’ll ask the same questions I always do:

1. Has it always done this or did it suddenly start? Did it gradually gotten worse? Hanging idle, not smell, I’m going to ignore that for now.
2. What mods or maint had you done leading up to this, no matter how insignificant it may seem?
3. Anything done to the exhaust? I’m wondering if your cat is getting plugged which is affecting the back pressure/ability for the bike to breathe. Can’t remember if there is an exhaust valve on this bike or not but if so is it functioning?
4. How many miles, what’s the maint like, up to date?

Let’s start here.

1. In the couple of years that i have the bike i never had this issue, it started at the end of last season, i cant remember if it started gradually or not.
But at least it did not get worse since then.
2. Nothing, its complete stock when it began. added a USB port and windscreen in the winter break.
3. Stock is also stock.
4. 19.000 miles, did a oil and filter change two years ago, and this winter again + spark plugs.

About the exhaust, i noticed that the schroud gets dirty faster than before, more black spots and stuff , but this could also be my imagination

 

[Brammers]

If you did the spark plugs... You've had everything off that could affect this.

I'd go back down to the spark plugs and rebuild it slowly and carefully.

There could be a leak between the airbox and throttle bodies, but you'd never see that for looking.

Is the air filter seated fully and without damage? No missing screws?

The map sensor reaction to being removed confirms at least that the sensor is working.

J

 

[bram2202]

It started before the new spark plugs, but never hurts to check them again.

Is ther a way to test the MAP sensor without MCS?

If there is a gasket in the filter housing that not seals correctly, would this effect the MAP sensor in any why?
The tubes connected to the MAP sensor are all hooked up to brass tubes in the throttle body, after the butterfly valves, if they are almost closed, a small leak would not impact in that bed right?

 

[Brammers]

The map sensor is just looking at air pressure. Any leak will throw it off.

My removal you seen what a massive leak will do. A small leak could easily do what you're seeing.

Can you confirm throttle freeplay is present on both full left and right steering positions please?

J

 

[bram2202]

I Checked, there is freeplay on both position.

 

[bram2202]

Small update.
Today was the first good warm day for driving, rode about 50 kilometers.
But the high idling issue is still there.

And I found out something else, if i just barley touch the throttle, the idle fluctuates between the 2.000 rpm and 2.500 rpm.
If i let go it goes back to 1.800 rpm (still to high) and if i continue to open the throttle the revs increase normally.

 

[Osoba Motocykliczna]

Small update.
Today was the first good warm day for driving, rode about 50 kilometers.
But the high idling issue is still there.

And I found out something else, if i just barley touch the throttle, the idle fluctuates between the 2.000 rpm and 2.500 rpm.
If i let go it goes back to 1.800 rpm (still to high) and if i continue to open the throttle the revs increase normally.

I have EXACTLY same issue and I am losing my mind over it. Did you manage to repair it?

 

[thomasss]

Hi
Someone solve this issue?
Best

 

[Brammers]

Check the vacuum host to the MAP sensor (under the tank) is in good condition and not split etc.

Can also be the TPS or IAT sensors causing throttle/fuelling to be off.

MAP sesnsor hose is where I would start - especially on older bike where the rubber can perish over time.

J