94 BMW k75 Problem - BMW Luxury Touring Community
 
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post #1 of 8 Old Nov 6th, 2008, 12:09 am Thread Starter
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94 BMW k75 Problem

Hey guys. I recently purchased a beautiful K75.
I had some problems come up, and was wondering if you guys could help me.
First off, the bike will not idle correctly. For some reason, no matter what I try, the bike does not want to seem to idle at anymore than 500-600rpm's. I've tried adjusting the idle, but the bike still doesn't seem to really raise the RPM's.
Another problem is the TPS. Could someone explain how to correctly set it? Thanks.
Third problem is that the bike surges. A lot. Basically, I will hold a constant throttle position, and the bike will speed up and slow back down constantly. Makes lane-sharing very interesting.
Well anyways, I rode back home today on my 13 mile commute, and my bike was really acting up. She was surging quite a bit. But here's the weird thing: After like 4 miles, the bike would not accelerate. I was cruising around 70-75mph, and I had to twist the throttle all the way open to maintain speed. Then after a while it started surging, and if I let of the throttle a little, it would start accelerating. Did this for the rest of my 13 mile commute. Thank god for no traffic.
Well when I got home and I looked at the pipe, which is the stock stainless k75 pipe, it was bronzen. Here's a picture:

This led me to believe that the bike was running extremely lean.
Here's the weird thing: I pulled the first two spark plugs and lo and behold, they were clean as a whistle. No carbon at all. Then I pull the last plug, it has a lot of carbon deposit on it. For some reason, while the first two cylinders were running lean/okay, the 3rd cylinder is running extremely rich.
Anyone here ever had this happen? It's really weird IMO.
Oh, and on deceleration and acceleration, my bike will pop and backfire. Just some more info.
If any of you guys could help me, that'd be great.
Thanks,
Nick.
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post #2 of 8 Old Nov 6th, 2008, 2:28 am
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Re: 94 BMW k75 Problem

Nick

Check your HT leads very carefully. I reckon the electrical pixies are escaping intermitently. http://www.ibmwr.org/ktech.shtml has lots of info.

Regards

Graham Wintersgill
On the bonnnie bonnie banks of Loch Lomond

2001 K1200LT

1995 K75RT now deceased
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post #3 of 8 Old Nov 6th, 2008, 5:26 pm Thread Starter
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Re: 94 BMW k75 Problem

I think my TPS is shot. It only clicks once. Do you know how it can be tested with a voltmeter?
Thanks,
Nick.
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post #4 of 8 Old Nov 6th, 2008, 7:22 pm Thread Starter
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Re: 94 BMW k75 Problem

So does anyone know if the TPS is supposed to click twice? Once when just off the idle, and then when the throttle is full open. Is this correct?
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post #5 of 8 Old Nov 6th, 2008, 9:29 pm
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Re: 94 BMW k75 Problem

Does that have a catylitic converter? could be plugged; maybe.....Jim
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post #6 of 8 Old Nov 7th, 2008, 2:29 am
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Re: 94 BMW k75 Problem

Nick

I know the surging is pointing you towards the TPS but I still think it is coil or HT lead. I did have a similar problem and when I ran the bike in a dark garage there were lots of sparks escaping.

You could have more than one issue but if your spark plugs are that different I would be looking there first. You said No 3 plug was vastly different - could this be caused by an intermintent spark? The TPS would affect all cylinders.

Low tickover - only runnning on 2 cylnders?
Surging - You have a crack in the HT lead insulation or intermitent coil. Ride along on 2 cylnders - 3rd one kicks back in - bike is making 50% more power so surges until the fault reappears - bike loses 3rd cylnder and 33% power so slows down until it kicks back in. What causes it to cut in and out? As you accelerate or deccelerate wires move about on your bike - closer or further away from the nearest ground.

Regards

Graham Wintersgill
On the bonnnie bonnie banks of Loch Lomond

2001 K1200LT

1995 K75RT now deceased
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post #7 of 8 Old Nov 7th, 2008, 9:18 pm Thread Starter
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Re: 94 BMW k75 Problem

Well bad news. My motorcycle is blowing out white smoke now. I pulled the plug on cylinder two, and it's fine, but cylinder three has oil on it.... so I am somehow getting oil into the cylinder 3.
Is there anything that is common to fail that allows oil to get into the cylinder?
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post #8 of 8 Old Nov 15th, 2008, 3:34 pm Thread Starter
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Re: 94 BMW k75 Problem

I'm happy to report that she's back up and running.
Of all the things, it was a bad spark plug.
She runs like a beauty now.
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