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Author Topic: Runs while on the center stand.  (Read 18131 times)

Offline gpcrane

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Runs while on the center stand.
« on: February 14, 2016, 12:35:54 PM »
I have been having grounding issues on my 87 K75s.  It was the classic starter motor would not work, the load shedding relay was not pulled in.  So I removed the starter motor and cleaned out 29 years worth of carbon.  I measured the brush length, the shortest one was 10mm, according to my Haynes manual the min. length is 6 mm.  I put everything back together and the bike fires right up, good as ever...until...

As soon as I push the bike off the center stand the engine dies.  I try starting again, the starter motor turns but no ignition.  Back on the center stand and it firers right up.  After a few times going back and forth with the center stand it is running off the stand and I ride a way for a test ride.

The bike feels normal, running great.  I stop for gas, and have no problems starting the bike and coming off the center stand.  I ride for a few more miles and the bike begins to cut out, lights stay on.  Then the bike dies.  Once again it will fire up on the center stand but dies off the stand.  I go back and forth once again and ride it home with no problems.

My first plan of attack with be to clean all around the center stand and check all grounds.  Pull the EFI connector and clean it up real well.  Any other thoughts out there?

Thanks.
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Offline TimTyler

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Re: Runs while on the center stand.
« Reply #1 on: February 14, 2016, 12:54:54 PM »
I would cut off the lower 75% of the two center stand legs. Then you can leave the stand "down" all the time and enjoy riding.  :hehehe
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Offline gpcrane

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Re: Runs while on the center stand.
« Reply #2 on: February 14, 2016, 01:06:40 PM »
What if I just have a chain attached to the center stand dragging to act a an earth ground?
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Offline jensk

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Re: Runs while on the center stand.
« Reply #3 on: February 14, 2016, 01:08:52 PM »
Have you checket the ingnition switch. It could be a classic issue og crud building up inside the ignition switch. There are several postings in here on how to diassemble and clean it
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Offline Laitch

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Re: Runs while on the center stand.
« Reply #4 on: February 14, 2016, 01:14:42 PM »
When the bike's put up on the center stand, force knocks to the rearward. When it's rolled off, the reverse tends to happen. I think you're on the right track, gp, looking for electrical connections that may be interrupted or wires that are being pinched and shorted when force in a certain direction is applied.

In addition to what jensk recommends, revisit your starter connections because that's where you worked last, then your frame ground connection and your four-pin plug beneath the tank—I like the idea that something so simple as cleaning an electrical plug can make a nice reversal of fortune. When a symptom is as consistently reproducible as this one, the solution would not seem to be far off.
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Offline Martin

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Re: Runs while on the center stand.
« Reply #5 on: February 14, 2016, 01:30:35 PM »
It might also be helpful if you can put the bike in a front wheel clamp (or get someone you trust to hold the bike), and with the bike running move your stands and wires around and see if anything is obvious.
Regards Martin.
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Offline gpcrane

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Re: Runs while on the center stand.
« Reply #6 on: February 14, 2016, 02:12:12 PM »
All good ideas.  I am going to get some contact cleaner today and go over the various plugs and such.  I tried disconnecting the batt. ground on the gear box but the ball end of my hex wrench broke off in the socket!  At least I know it is on tight. My lights never seem to flicker or go out now so I feel the starter ground/load shedding relay issue is resolved.  I can hear my fuel pump running so I keep thinking the problem is with the EFI/coils loss of signal (maybe the ignition switch as suggested) or in that area.  I hate how tight the bend is on the cable that plugs in to the EFI.  I don't have a wheel stand so I may need to get some one to hold the bike while I do some testing.  BTY I have had the same issue with the bike on the side stand starting but then dies when the stand is pulled in.  Clutch in/out has not effect on the problem.

Thanks.  Will update as this goes.
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Offline johnny

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Re: Runs while on the center stand.
« Reply #7 on: February 14, 2016, 02:16:07 PM »
greetings...

id put it in gear and ride it off the center stand... tach it up and give it the pelvic thrust and drop the clutch all in one fluid motion...

j o
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Offline Laitch

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Re: Runs while on the center stand.
« Reply #8 on: February 14, 2016, 02:25:43 PM »
Quote from: johnny on February 14, 2016, 02:16:07 PM
greetings...
id put it in gear and ride it off the center stand... tach it up and give it the pelvic thrust and drop the clutch all in one fluid motion...
j o
Right out of Clymer BMW K-Series⋄1985–1997, Couples Edition: Chapter 3, Lubrication, Maintenance and Tune-Up
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Offline johnny

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Re: Runs while on the center stand.
« Reply #9 on: February 14, 2016, 02:33:32 PM »
rodger that...

looked it up... bmw recommends dry lube...

i thinks tim tiorler is selling that on amazon...

j o
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Offline gpcrane

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Re: Runs while on the center stand.
« Reply #10 on: February 14, 2016, 02:49:06 PM »
Found the problem.  It's that fucking bend in the EFI cable.  I removed the EFI and had it plugged in and the bike started right up.  When I put it back in and moved the cable slightly it ran until I moved the bend.  There is a bad wire in there.  Fuck!

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Offline Laitch

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Re: Runs while on the center stand.
« Reply #11 on: February 14, 2016, 03:01:19 PM »
Quote from: gpcrane on February 14, 2016, 02:49:06 PM
Found the problem.  It's that fucking bend in the EFI cable.  I removed the EFI and had it plugged in and the bike started right up.  When I put it back in and moved the cable slightly it ran until I moved the bend.  There is a bad wire in there.  Fuck!
No need to get haired-out, gp. You've found the problem and that's good. :clap: Someone might come along with a solution or useful observation. In the meantime, try splinting the cable to stabilize it while it's in the position that makes the bike run then jog the bike some to test it. Also, make certain the problem doesn't stem from poor pin contact between the connectors.
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Offline gpcrane

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Re: Runs while on the center stand.
« Reply #12 on: February 14, 2016, 03:51:58 PM »
I cut back the outer shell of the cable to where the bend is at.  The shell is a hard and at the bend it was very much pinching the wires.  I have messed with each wire while the bike is running and can't get it to cut out.  Now that I have the shell cut back and the rubber boot pulled back in place between the connector and cable I have less strain at the bend with the EFI in place.  Will also use some cable ties to keep things in place.  Yesterday I went over the pins on the connector with some 1500 sandpaper and made them shine.

If BMW has just lipped the EFI over the need for such a tight 180 deg. bend would have been avoided.  It's crap design engineering that only made this last for 29 years.    :2thumbup:
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Offline Laitch

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Re: Runs while on the center stand.
« Reply #13 on: February 14, 2016, 04:07:21 PM »
Quote from: gpcrane on February 14, 2016, 03:51:58 PM
If BMW has just lipped the EFI over the need for such a tight 180 deg. bend would have been avoided.  It's crap design engineering that only made this last for 29 years.    :2thumbup:
Too late now. My connector's got ten more years! :yippee: We're depending on you, gp, for a permanent solution. Once you get this rigged, ride the hell out of the bike and report back, please.
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Offline Laitch

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Re: Runs while on the center stand.
« Reply #14 on: February 15, 2016, 08:27:15 AM »
Is that plug fairly easy to disconnect by hand, gp, or do you really need to pry back on that latch that sticks out of the tool box and firmly pull on the plug to get it loose?
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Offline gpcrane

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Re: Runs while on the center stand.
« Reply #15 on: February 15, 2016, 09:39:03 AM »
Once the screw on the left side of the connector is backed out the connector comes out easily pulling from the right side.  I can disconnect by just pulling the on the right side of the connector, I don't need to get leverage by pulling on the cable.  I also found I put less stress on the cable if I slide and angle the box out first then disconnect.  Disconnecting first the way my cable was I had to flex the bend even more to get it past the frame.  When screwed in the connector does not have any wiggle.
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Offline Laitch

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Re: Runs while on the center stand.
« Reply #16 on: February 15, 2016, 09:41:54 AM »
I could use a photo of that situation, gp, if you've got nothing better to do.
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Offline The Mighty Gryphon

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Re: Runs while on the center stand.
« Reply #17 on: February 15, 2016, 09:58:55 AM »
Quote from: gpcrane on February 15, 2016, 09:39:03 AM
Once the screw on the left side of the connector is backed out the connector comes out easily pulling from the right side.

???????!!!   Maybe my '94 K75's are different, but I have never had to unscrew the big connector on the Jetronic module to get it off.  I can't recall any connectors on my bikes that need to be unscrewed. 

+1 on a photo of what you're talking about.
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Offline K1300S

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Re: Runs while on the center stand.
« Reply #18 on: February 15, 2016, 10:02:10 AM »
yes, pic would be good.   bmw used screws to hold connectors on the car version of the bosch ecu's.  have only seen the spring catch on K's.
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Offline Laitch

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Re: Runs while on the center stand.
« Reply #19 on: February 15, 2016, 11:32:14 AM »
OK. Here's a blurred but well-intentioned photo of the latch taken by means of the last few electrons in my camera's battery.

On the right is the bright metal latch. There's an opening in the center of that latch that receives a molded projection—let's call it a "tongue"—on the cable side of the plug. On the left side of the plug should be a molded  hook that is received by an opening on the left side side of the ECU. The plug gets hooked into the left side then the plug is pushed into the latch on the right side. To release the plug, a screwdriver is put through the hole you can see in the tool box above the plug and then the latch is pried to the right: while it's pried you pull the plug from the assembly.

Latches sometimes lose their tension then the plug gets loose enough to detach intermittently. Pushing the latch to the left when it's empty usually will create sufficient tension to keep the assembly locked after the plug is engaged.

Is that what you're seeing, gp? Take a good look at both sides of your plug. Are the hook on the left side and the projection on the right side still there? More pictures coming from others, I'm sure, or when my camera's battery is recharged.


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Offline rbm

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Re: Runs while on the center stand.
« Reply #20 on: February 15, 2016, 02:43:56 PM »
The retainer spring to which Laitch refers is shown below:


It retains the connector in place by capturing this small protrusion on the connector:


If this protrusion is worn or missing, or the retaining spring clip is weak, the connector will not be held in place.  The extreme angle of the cable can lead to problems, so routing the cable is important.  Having said that, I've owned K-bikes for decades and never encountered problems with this system.
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Offline Laitch

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Re: Runs while on the center stand.
« Reply #21 on: February 15, 2016, 04:20:29 PM »
Photos of the hook end of the plug that will be hooked into a slot on the left side of the box. After it's hooked, you pivot the plug into its connections then push it so it will latch molded tongue (retainer clip in rbm's photos) into the hole in the latch plate.


I'm really interest to see what's happening with your assembly, gp.



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Offline gpcrane

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Re: Runs while on the center stand.
« Reply #22 on: February 15, 2016, 05:12:50 PM »
Opps, I feel silly now.  The screw I mentioned does not hold the connector in place.  It is the same as the ones pictured above.  I just assumed it was like other connectors I have come across so I always backed out the screw before trying to disconnect.  It is just held in place with the hook and retainer clip.

I tried to post a few pics but there was a error and my first post did not get posted.  I will try again.

Sorry for the confusion, Greg  :dunno2: :dunno2:
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Offline gpcrane

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Re: Runs while on the center stand.
« Reply #23 on: February 15, 2016, 05:18:10 PM »
EFI slightly pulled out, you can see the tight bend.  Was worse before I cut back the cable shell.
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Offline Laitch

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Re: Runs while on the center stand.
« Reply #24 on: February 15, 2016, 05:36:36 PM »
That's insane! How about a head-on shot, gp? Try to make it clearer than mine. There's just something not right there.
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