K11 Owners Group

BMW_Mick

Hi,

My '93 K11LT backfires when I close the throttle fully while slowing down. There is also a 'hole' when I open the throttle quickly. The engine doesn't exactly bog down, but there is a definate hesitation at low revs but once it picks up it's fine.

This is my 5th K 100/1100 and never had anything like this before. I'm thinking that it's something to do with the injectors but any ideas are welcome. Oh, the fuel consumption round town has dropped through the floor too.

HELP!! Lol.

Thanks,
Mick
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'93 K1100LTSE, ABS1 in Black 'Connie'

Ernie-NH · Posted: Tue Jul 12, 2011 10:26 am Post subject:

Good morning Mick...

Most bikes that I have (5) and those that I know, will 'backfire or 'rumble' when engine braking. Unburnt fuel/air mix gets forced out into the exhaust and ignites while the exh. valve is open or partially open. Is your symptom a true loud report, or is it the multiple 'popping' that is so common ?? Have you tested your HES ? Has the Throttle Body been sync'd lately ? Valve clearances been checked ??

Best regards.......// Ernie in NH
_________________
AMA,, American Deaf Bikers
Airhead Beemers Club
'11 G650gs
'95 K1100LT
'76 R100/7

BMW_Mick · Posted: Tue Jul 12, 2011 12:25 pm Post subject:

HI Ernie,

Ok, time to show my lack of knowledge... What's the HES? And it's multiple popping, but really quite loud.

As for the throttle body, not by me, only had the bike just over 3 months, ditto with the valve clearances.

Just seems odd, the last k11LT I had never did it nor the K12LT or K100RS' either. Something that did occur, I think the throttle should shut off completely until the revs get down to normal idle - or is that the HES?
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'93 K1100LTSE, ABS1 in Black 'Connie'

Phil Marvin · Posted: Tue Jul 12, 2011 12:44 pm Post subject:

Hi, Mick,
Also, the welds on the exhaust have been known to crack/break, allowing additional air (oxygen), with the corresponding backfiring. Check the exhaust very closely, especially where the pipes join the muffler.
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Ride Safe,
Phil Marvin in El Paso, TX
'94 K75A/3
'95 K75RTP

Jim · Posted: Tue Jul 12, 2011 12:49 pm Post subject:

mtnroads · Posted: Tue Jul 12, 2011 3:26 pm Post subject:

Sounds lean to me which would account for the backfiring as well as the soft spot in power delivery. Could be caused by an air leak such as cracks in the intake boots - the rubber boots from throttle body to the head. There are ways to test by spraying oil on them I believe. I would at least do a close visual inspection.
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2012 R1200RT Midnight Blue
95 K1100LT Graphit (sold)
01 R1100RT Black (sold)

Rafal · Posted: Tue Jul 12, 2011 4:47 pm Post subject:

Jim · Posted: Tue Jul 12, 2011 5:47 pm Post subject:

Thanks, Rafal - I meant sensor. Embarassed

_________________
Jim
1997 K1100LTSE 94,000 - still has gremlins!
1995 R100RT Classic 16,650 crashed - repaired!
1992 K75RTP 46,000

"We shall not all die, but we shall all be changed."

Ernie-NH · Posted: Tue Jul 12, 2011 8:59 pm Post subject:

Hello Mick...

Check the "tech" section about four threads down ( ie: Missing/Stuttering ) and you'll see that Scott has given us a pictorial of how to test the TPS and what the voltage values across pins 1 and 4 should be when connected as well as disconnected, assuming the ignition switch is ON ! As for testing the HES ( Hall Effect Sensor ) check the "stickies and you'll find the famous "hair dryer test".... Vacuum leak testing is mostly visual ie: cracks in lines and boots etc... Phil has told you where to look for leakage in the exhaust output.. and you should get yourself a good digital volt/ohm meter for about $30 USD and you're on your way !!! As far as "valve clearances" are concerned, it would be great if a BMW service mechanic would let you look over the shoulder so that you could do it yourself (maybe) next time.... same goes for Throttle Body synchronization.

Good Luck....// Ernie in NH
_________________
AMA,, American Deaf Bikers
Airhead Beemers Club
'11 G650gs
'95 K1100LT
'76 R100/7

Mystic Red · Posted: Tue Jul 12, 2011 9:54 pm Post subject:

beemeerr11 · Flying Brick Rider Joined: 05 Mar 2006 Posts: 168

merlin geikie · Posted: Fri Jul 15, 2011 5:10 am Post subject:

Mick, Google is your friend and there is a TON of info on the big K.

Do you have a workshop manual? Over in UK you will find em on ebay or amazon etc.

You got good tools? Start with decent stuff and build as you needem.

Folks on this site are great with a HUGE wealth of experience and there is the KBMW list at micapeak and other sites, this site has REAL people though Wink

Put a bottle of Caltex Techron 5000 through a few tanks to clean the injectors.

Throw in a set of plugs if you don't know these are new, BUT read the old plugs and they will tell you a lot (see TED's page).

Check the intake plenum boots as mentioned.

You may be in for a new O2 sensor as, if faulty could run you rich.

Keep researching and asking questions and before too long, you will know a dang LOT about your bike, will be mechanically more able and will be able to help other folk, in your position now Wink

Hang in there Mate

merlin from a damp downunder oz

Mystic Red · Posted: Sat Jul 16, 2011 3:57 pm Post subject: