Exhaust evenness

DavidR8

Site Supporter
Joined
May 31, 2017
Messages
1,220
Location
Vancouver Island, British Columbia
Bike
2013 BMW R1200RT
STOC #
8968
I was droning along on my commute home tonight and I noticed that STella runs unevenly.
Listening to the exhaust note it sounds like this:
Brum, brum, brum, brum, pop, pop, brum, brum, brum,pop, brum, brum, brum, brum,pop,pop,
Or something along those lines. Basically it doesn't sound even.
This maybe completely normal because of the 360 degree crankshaft design.


Sent from my iPhone using Tapatalk
 

Scooter

This space for rent...
Joined
Oct 12, 2005
Messages
1,779
Location
Germantown, WI
Bike
2019 BMW R1250RT
STOC #
5929
What RPM are you running when you notice this? Does it change pattern at different engine speeds?
 
OP
OP
DavidR8

DavidR8

Site Supporter
Joined
May 31, 2017
Messages
1,220
Location
Vancouver Island, British Columbia
Bike
2013 BMW R1200RT
STOC #
8968
Anywhere between 2000 rpm and as high as I'm willing to take it. Obviously the higher rpm makes it impossible to hear the individual pops.
2000-3000 is prime to hear it.


Sent from my iPhone using Tapatalk
 

jfheath

John Heath
Site Supporter
Joined
Mar 18, 2006
Messages
2,786
Age
69
Location
Ilkley, W Yorkshire, UK
Bike
2013 ST1300 A9
2024 Miles
000679
STOC #
2570
My 06 used to make popping sounds, and at the time, so did most of the ST1300s in the club - but this was usually associated with either coasting along or coming off the throttle - however gently. Using engine braking it always sounded as though I had a highly tuned sports bike had just ridden up behind me. This wasn't a backfire noise, more of a bubbly burbling.

But I don't recall it doing it when accelerating. The only time I ever had that was on the ST1100 when one of the vacuum tubes (that you use for balancing the carbs) popped off.

My 09 model has never done this - but the ECM is different and the engine behaves differently in other ways too.
 
OP
OP
DavidR8

DavidR8

Site Supporter
Joined
May 31, 2017
Messages
1,220
Location
Vancouver Island, British Columbia
Bike
2013 BMW R1200RT
STOC #
8968
My 06 used to make popping sounds, and at the time, so did most of the ST1300s in the club - but this was usually associated with either coasting along or coming off the throttle - however gently. Using engine braking it always sounded as though I had a highly tuned sports bike had just ridden up behind me. This wasn't a backfire noise, more of a bubbly burbling.

But I don't recall it doing it when accelerating. The only time I ever had that was on the ST1100 when one of the vacuum tubes (that you use for balancing the carbs) popped off.

My 09 model has never done this - but the ECM is different and the engine behaves differently in other ways too.
Thanks
If I'm sitting at a light and I hold the throttle to 3000 rpm I can hear the irregular rhythm. Makes me think that complete combustion is not occurring in the cylinder and a small amount of unburned gas is igniting in the exhaust.


Sent from my iPhone using Tapatalk
 

SupraSabre

48 Years of SoCal Lane Splitting/Commuting-Retired
Site Supporter
Joined
Nov 20, 2005
Messages
9,498
Location
Cedar City, Utah
Bike
12/04 ST 1300s
2024 Miles
000145
STOC #
5901
Thanks
If I’m sitting at a light and I hold the throttle to 3000 rpm I can hear the irregular rhythm. Makes me think that complete combustion is not occurring in the cylinder and a small amount of unburned gas is igniting in the exhaust.


Sent from my iPhone using Tapatalk
This is why EVERYONE should have at least two ST1300s. This way if only one is acting a particular way, you know you have an issue. If both bikes do the same thing...it's just the way they are! :rofl1:
 

jfheath

John Heath
Site Supporter
Joined
Mar 18, 2006
Messages
2,786
Age
69
Location
Ilkley, W Yorkshire, UK
Bike
2013 ST1300 A9
2024 Miles
000679
STOC #
2570
Thanks
If I'm sitting at a light and I hold the throttle to 3000 rpm I can hear the irregular rhythm. Makes me think that complete combustion is not occurring in the cylinder and a small amount of unburned gas is igniting in the exhaust.
No, mine never did that sort of thing (except when the plug caps / leads went south), but then it wouldn't pull away unless I really gave it high revs to generate sufficient spark. It might help if you could record the sound. My skills run out at this point I'm afraid.

But I am good at asking myself stupid questions - that is unless the question that I ask is something that I have overlooked.

SO - You just done the throttle bodies - did it do this before then ? You posted a video relating to a VFR and it spurred me to try and find out about this dark art. I found another video again for another VFR800 where the chap insisted that a hose to the MAP sensor should be plugged for that particular VFR800.
The ST1300 manual says nothing about that - it just says to disconnect the suction hose from the PAIR reed valve cover and plug the hole. It also says to hold the revs above 2000rpm for 5 seconds so that the MAP sensor reports a fault to the ECM - (I assume it then ignores whatever info it gets from the sensor).

So I'll bow out at this point, but I'm watching the comments very closely - always trying to learn something. The last time I took my bike in to the dealer was 'cos my valve clearances were out and I didn't have the time or enthusiasm to do the job myself at the time. I also asked them to synchronise the starter valves, as my bike didn't sound as sweet as a friends who had just had his balanced.

When I got it back, they had shimmed the left side valves, said the right side were OK (they were, but right on the edge of being too tight), and they said the throttle bodies were spot on. Not convinced, I looked under the tank and the airbox had never been taken off ! They also introduced an oil leak because the rubber gasket hadn't been fitted properly or sealed around the half moons, and the engine sounded rather boomy. So - yes, I will be watching carefully.
 
OP
OP
DavidR8

DavidR8

Site Supporter
Joined
May 31, 2017
Messages
1,220
Location
Vancouver Island, British Columbia
Bike
2013 BMW R1200RT
STOC #
8968
It might help if you could record the sound.
Yes, I think I'm going to try and record the sound. Stay tuned.

SO - You just done the throttle bodies - did it do this before then ?
I believe it did do this before the starter valve sync.

You posted a video relating to a VFR and it spurred me to try and find out about this dark art. I found another video again for another VFR800 where the chap insisted that a hose to the MAP sensor should be plugged for that particular VFR800.
The ST1300 manual says nothing about that - it just says to disconnect the suction hose from the PAIR reed valve cover and plug the hole. It also says to hold the revs above 2000rpm for 5 seconds so that the MAP sensor reports a fault to the ECM - (I assume it then ignores whatever info it gets from the sensor).
I'm curious about this too. I wonder why the MAP sensor is left open. I don't suppose it really matters though as I expect without a vacuum applied it would still throw a code.

When I got it back, they had shimmed the left side valves, said the right side were OK (they were, but right on the edge of being too tight), and they said the throttle bodies were spot on. Not convinced, I looked under the tank and the airbox had never been taken off ! They also introduced an oil leak because the rubber gasket hadn't been fitted properly or sealed around the half moons, and the engine sounded rather boomy. So - yes, I will be watching carefully.
So clearly they didn't do all the work they said they would. I'm sure they charged you for it though :-/
 
OP
OP
DavidR8

DavidR8

Site Supporter
Joined
May 31, 2017
Messages
1,220
Location
Vancouver Island, British Columbia
Bike
2013 BMW R1200RT
STOC #
8968
I didn’t manage to capture the exhaust sound so well but in this video you can see the rpm fluctuate. I’m holding the throttle dead still at around 2100 rpm and again at near 3000 rpm. At around 20 seconds the rpm drop and then recover. I have not moved the throttle so I have no idea what’s going on. Throttle cables have the correct free play.
https://youtu.be/IPSRIoxvUgA

I’ll try another to capture the exhaust sound.

Edit: I just listened to this using headphones and I can hear the uneven exhaust.


Sent from my iPhone using Tapatalk
 
Last edited:
Top Bottom