Loss of power/engine noise

Joined
Sep 6, 2017
Messages
13
Location
United Kingdom
Bike
Bandit 1200S
Dear all,

I have a 99' st11 with ~50k miles. I bought it maybe 6 months ago.

I was riding at a steady speed of ~70mph (engine was warmed up) and I started to notice a loss of power. It would stutter and all of a sudden gain power again and judder forward. I have had this with a previous bike and it turned out to just be a fuel pipe. However, I tried to nurse it home as best I could but a couple of miles down the road I heard a couple of REALLY LOUD bangs that sounded like they were coming from the engine. At this point I pulled over, the engine died and I had to get recovered. The bike will start now, but obviously I am not sure what's wrong with it. It felt like it wasnt running on all four cylinders.

I am pretty new to Pans but the engine also sounds more noisy to me now, but I am not an expert on how it should sound. I just know it sounds different to me now. I am hoping it is something simple!
 
Joined
Feb 25, 2016
Messages
4,759
Location
Northumberland UK
Bike
VStrom 650
More info would be good.
Bang like a back fire?
When you re started was there any blue smoke from exhaust.
What's the oil level like.
Had you done any work recently.
Have you had the plugs out to see if they say anything other than loveliness.
Upt'North.
 
Joined
Aug 10, 2015
Messages
2,029
Location
Fort Worth, Texas
Bike
91 ST1100/06 ST1300
Any other symptoms you noticed?
-fuel smells
-over temp reading
-water or oil leaks
-water level
-oil level
-any indications of overtemp in the wiring around the battery or alternator?
-what is the corrosion like in the area of the alternator...or around the rear of the alternator?
 
OP
OP
Joined
Sep 6, 2017
Messages
13
Location
United Kingdom
Bike
Bandit 1200S
Hi both,

I will try and provide as much information as possible.
Unfortunately due to the fact I wear earplugs I couldn't distinguish the 'bang' very well - except that is was very loud and didn't seem to be associated with any particular RPM or speed, it happened maybe three times in the course of a minute. I pulled over after.
After pulling over there did seem to be a 'hot smell' that didn't reappear when I started the bike up again. When I started the bike up again there was no blue smoke, or any smoke at all. At no point was the temp gauge over 1/2 during the journey.

I haven't done any work on the bike recently - all the fluid levels are adequate and within range, there are no visible water/oil leaks.

I plan on taking the bike apart in the next few days and investigating the plugs and thoroughly inspect the alternator and wiring.
 

Slydynbye

Will ride for Pie
Joined
Sep 3, 2007
Messages
1,596
Location
Fremont, California
Bike
2000 ABSII
STOC #
7331
Loss of power makes me think your Fuel cutoff diaphragm is failing. Bypass it and perhaps replace fuel filter before diving in deeper.
 

kiltman

Site Supporter
Joined
Apr 27, 2013
Messages
3,280
Age
68
Location
Stratford, Ontario Canada
Bike
2002,ST1100ABS
STOC #
8826
Check the red connector to the main relay. under the left panel. Put it on the Center stand start it, leave it neutral and deploy the side stand, if it shuts off then jump the two green wires on the side stand switch.
what you describe happens when there is a poor electrical connection at the main relay or shut off switch, the engine may run rough like it’s missing and backfire.
that’s my take on the situation
 

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
It is possible that one of the four vacuum hoses has become detached. They are short lengths of black tube that protrude from behind each cylinder head (roughly above the spark plugs) and are used to plug in vacuum gauges when balancing the carbs. In the UK they are capped off. The cap is removed in order to connect the gauge, which saves having to access the connection at the base of each carburettor, way down in the Vee, but it is not unknown for the cap to come off, or the other end to be pulled during a service, to become 'unplugged' at some point in the future. If it is this, you need a flashlight and a set of long nosed pliers to get it back on.

If one of these comes off, the symptoms are a serious loss of power, a lot of backfiring, and it feels / sounds like it is a cylinder down.

Sorry, I don't have an 1100 any more and can't provide a picture. Someone else may chip in.

[Edit]
Forgot to say - one of the four tubes isn't blanked off like the other three. This is the rear one on the right hand side. It is connected to the petrol shut-off valve - the suction from the engine keeps the valve open. If that is sucking air from outside, the 'petcock' will not be kept open and the engine will not get its fuel.
[/Edit]
 
Last edited:
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
Interesting problem. Sounds like gas may have been building up in the muffler due to no spark. And then when the spark returns, BAM !!!

But that's just a WAG, for sure !!!!

Now that the bike is running, take it for a ride at 60 mph, then turn the RUN/STOP switch to the "STOP" position until the speed gets down to say, 45 mph and then turn the RUN/STOP switch to the "RUN" position and see if the "BAM" occurs. WARNING : Of course you may also damage your muffler by doing this.
 

Erdoc48

Site Supporter
Joined
Jan 25, 2009
Messages
1,422
Age
59
Location
Myrtle Beach, SC/ Sometimes Colorado
Bike
94/00/04 STs, FSC600
Stupid question...how is your battery? I’ve had 2 bikes (V30 Magna and my 00 ST) with bad batteries and in both cases, when on the road, it would backfire and run terribly. It would have been running on the alternator at that time and a new battery solved everything. Carb issues can definitely be at fault here, but I’d check the voltage of the battery, just to be sure.
 
OP
OP
Joined
Sep 6, 2017
Messages
13
Location
United Kingdom
Bike
Bandit 1200S
Thanks for all the suggestions everyone, these will keep me busy the weekend! Hoping that it is just something simple like loose connections.
 

kiltman

Site Supporter
Joined
Apr 27, 2013
Messages
3,280
Age
68
Location
Stratford, Ontario Canada
Bike
2002,ST1100ABS
STOC #
8826
Took me awhile to discover the sidestand switch was the issue on my bike. I had checked all my connections, and everything seemed to be in order. I would be riding along, it would hesitate, then a loud backfiring bang. As I mentioned above you can jump the two green wires just above the green connector under the left side panel after you determine if the sidestand switch is the issue.
 
Last edited:
Joined
Apr 7, 2007
Messages
624
Location
Tacoma, wa
Might I suggest that you turn over the engine until it starts, and then shut it down and pull the individual spark plugs - the one(s) that are wet and smell of gas are your starting point
 
Joined
Feb 25, 2016
Messages
4,759
Location
Northumberland UK
Bike
VStrom 650
See, it just goes to show......Kiltman with a real out of the ball park hit.
Who would of thought of a sidestand switch fault, not saying it is, but who would of thought it.
God bless all participants of this truly great forum. And I haven't even had a wee dram yet.
Upt'North.
 

kiltman

Site Supporter
Joined
Apr 27, 2013
Messages
3,280
Age
68
Location
Stratford, Ontario Canada
Bike
2002,ST1100ABS
STOC #
8826
See, it just goes to show......Kiltman with a real out of the ball park hit.
Who would of thought of a sidestand switch fault, not saying it is, but who would of thought it.
God bless all participants of this truly great forum. And I haven't even had a wee dram yet.
Upt'North.
Well last year in October on a holiday weekend I sat on the side of the road for two hours trying to find the fault. I thought it was my red wire main relay, then by accident I deployed the side stand in neutral and the bike would shut off. Fortunately I had a wiring diagram with me and was able to determine which wires I could jump. A few days prior this backfire/engine running rough intermitantly plagued me. I would pull the bike to the side of the road, strip off the tupperware put it back together and be good for awhile. ( I have an emergency wiring kit with various connectors for just an emergency) The issue has come up before on the forum.
I'm curious if this is the same issue. In the meantime, I will sit back with a wee dram of Japanese whisky ;)
 
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
BTW, I carry a spare side stand switch ( along with a spare ECU ) in my top box that I got cheap off EBay. That way, they will never need to be replaced.
 

kiltman

Site Supporter
Joined
Apr 27, 2013
Messages
3,280
Age
68
Location
Stratford, Ontario Canada
Bike
2002,ST1100ABS
STOC #
8826
BTW, I carry a spare side stand switch ( along with a spare ECU ) in my top box that I got cheap off EBay. That way, they will never need to be replaced.
You could also replace them in rotation every year so you know in fact they are working, part of that preventative maintenance thing .... ( kiltman last scene ducking for cover) ;) :run1: .... Bush....Bush....Bush.....
 
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
Bike
'98 ST1100
STOC #
8470
Kiltman : Great idea !! Thank you !!

I have no idea if I bought a bad ECU ( Ignition Control Unit, or what I call an ECU ) or bad side stand switch. I declare to all on this Forum ( especially Mr. Bush ) that I will be switching them religiously ever spring ( to exercise them and to keep them both honest ) when I do most of my PM work.


Erdoc : Looks like Honda calls it an Ignition Control Module, but a CDI (??) for short. See : https://www.partzilla.com/catalog/honda/motorcycle/1998/st1100-a/cowl-stay ( Item #4 )
However, in reference to Item #2, they call it a Spark Unit ( whatever ).

I got mine for $30 off EBay.
 
Last edited:
Top Bottom