K11 Owners Group

Don Sproule · Posted: Thu Oct 09, 2014 9:03 pm Post subject: Surging issue

I hope someone here can help me with this.
There is a surging problem with my 95 LT that has been bugging me for about four or five years.
The bike starts and runs well. Goes well enough under full throttle but has a hesitation when the throttle is kept at a steady speed. The problem seems to manifest itself more strongly in warm/hot weather.
The symptoms feel exactly like the fouled injector I had on a K100RS I used to own. Some good fuel cleaner cleared it up within two miles.
I have had my injectors tested. The fellow said they were spot on and not in need of cleaning. I had poured gallons of different fuel treatments/cleaners of various types through it over the years.
I have had the valves checked (had to shim one in cyl #1 as it was a bit tight).
Changed the plug wires (new Magnecors), replaced the plugs (new Bosch- the spendy ones) and the throttle bodies synched.
I am running out of ideas. Maybe an air leak? I tried running propane gas around the intake with the bike running but noticed no reaction.
My next step will likely be to order the intake breather hose and try that.
In the meantime, anyone here had a similar experience? I'm about due for a shortcut.
Thanks.

Don

bikesnbones · Big Brick Rider Joined: 03 Aug 2014 Posts: 74

Many years ago I owned a Yamaha GTS1000 injection, and this was a commonly reported problem with the bike.
It was with mine, but todays owners seem to have it sorted.
It may be worth having a look on their tech forums for some hints, as I know that those guys found a way of erradicating the problem.

https://www.mail-archive.com/gts-1000@listserv.uga.edu/msg04428.html

Scott_Anderson · Posted: Fri Oct 10, 2014 7:09 pm Post subject:

2 things come to my mind.

Intermittent HES flaking out. (check with hair dryer or heat gun)
FPR and/or fuel pump acting up.... (check your pressure -hot and cold)

Not saying that either one is your cause, but they are 2 that you didn't list.
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1995 K1100LT 0302044
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1997 K1100LT 0302488(R.I.P.)
1997 R1100RT ZC62149(sold)

Don Sproule · Posted: Fri Oct 10, 2014 8:04 pm Post subject:

Thanks, Scott.
I doubt if it's either one of those.
The problem does show at cool engine and ambient temps.
The problem is almost subtle. Most wouldn't notice it unless they know K bikes.
Sure it's not pump or pressure as it always starts well and goes well when whipped.
Kinda suspect it may be a bit of a vacuum leak but am too lazy to rip apart the intake.
The mechanic I use can't seem to track it down. He doesn't even really notice it.
He's worked on a lot of BMWs but not much on Ks.

SugarHillCTD · Posted: Fri Oct 10, 2014 9:15 pm Post subject:

Don,

I have an odd suggestion here-

Check ALL the electrical ground connections. I had similar problems- surging- on my previous K-RS. Found a loose frame to engine ground wire. Why did it cause my problem? Don't know but tightening a single bolt fixed it.

Good luck.

John
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'92 K100RS4V Pearl White SOLD
'04 K1200GT
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Don Sproule · Posted: Fri Oct 10, 2014 9:55 pm Post subject:

Thanks, John.
I've tried all of the obvious grounds but will try to take some time and look deeper.

Don

whyoldbill · Posted: Fri Oct 10, 2014 9:56 pm Post subject:

Throttle Position Sensor?
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Don Sproule · Posted: Sat Oct 11, 2014 4:02 am Post subject:

Checked.

Number 6 · Posted: Sat Oct 11, 2014 4:18 pm Post subject:

Is it a model with catalytic exhaust and oxygen probe?
How is the overall full consumption?
Does it happen when the engine is cold or warm or both?
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94 K1100LT

Don Sproule · Posted: Sat Oct 11, 2014 8:46 pm Post subject:

It's in Canada and appears to be EU model. No O2 sensor.
The miss is always present when at steady speed. Hard to notice when cool and more noticeable in hot weather.
Fuel mileage is steady, about 45+miles per Imperial gallon.
Starts and idles fine. Seems good when accelerating.

Number 6 · Posted: Sat Oct 11, 2014 9:04 pm Post subject:

Sounds like running lean, if you mix a significant amount of ethanol with your gas, it kind of acts like that.
Did you have the "CO" potentiometer adjusted? You need a gas analyzer for that.
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94 K1100LT

Don Sproule · Posted: Sat Oct 11, 2014 11:36 pm Post subject:

I do everything I can to avoid ethanol. When travelling, I will take regular if the premium has ethanol. Here, the only pure gas is premium.
I don't know who would have an analyzer here. I will put the idea into my list of things to check.
Thanks.

Don

552255 · Posted: Sat Oct 11, 2014 11:37 pm Post subject:

..Don't know if it will give any help but I had used propane, and starter spray to try and find vacuum leaks. No change in idle, etc. Later I replaced throttle body boots, hoses with obvious leaks. Found they were cracked thru but did not respond to the 'test', at least that I could tell.

...maybe under "load", ie. higher rpm's, the air leak would show itself better?...if that is the issue. "Surging" sounds more like a fuel problem...
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Don Sproule · Posted: Sun Oct 12, 2014 3:56 am Post subject:

I'm suspecting that it's sucking air somewhere.
It's not so much a surge as a hesitation or slight 'stumble'.
Imagine how a clogged fuel injector behaves and that's exactly the symptom.
I really didn't want to have to order all the rubber parts (we all know how proud the Germans are of their rubber) and start tearing it all down. The other unpleasant option is digging around until I find out what piece(s) may need replacing and then ordering and waiting for the part(s). Meanwhile, the bike is in pieces taking up space.

Don