Bike Won't Start... Sometimes. Any Sugestions? - K-Bikes.com - Excellence in Motion
 
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post #1 of 10 (permalink) Old Apr 18th, 2010, 10:51 pm Thread Starter
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Bike Won't Start... Sometimes. Any Sugestions?

I'm not quite sure how to diagnose my problem, so any insight as to what the issue might be would be greatly appreciated.

I have a 1990 BMW K75S with 14,000 miles. In the past 2-3 days, I have not been able to start the bike. The first time it happened, I went into the garage in the morning for the day's first ride, turned the key, but the head light didn't turn on. All of the lights on the speedo lit up no problem, but the headlight was noticeably off. When I tried to fire it up... all I heard was the fuel pump buzzing.... but the engine never even tried to turn. Later that day, I had someone push me and I started it by just popping the clutch in 3rd gear. After that, the bike started again using the ignition with no problems, 10-15 times within 2-3 days.

Then today, I rode the bike for about 2 hours on the expressway. I got home, pulled into the garage and flipped the kill-switch. As soon as I hit the kill-switch, I noticed that the headlight turned off (before I turned the key to off). I turned the key to off, then back to on... and I had the same problem. There was no headlight again, and the engine wasn't turning when I tried to start it.... all I could hear was the buzzing of the fuel pump. I went inside, had a beer, went back outside... and the bike started again, no problem.

So, I'm not sure how to diagnose the problem in order to fix it. Does anyone have any suggestions as to what might be causing this problem? I'm hoping the K-Bike community will be able to share some wisdom and insight, as it would be greatly appreciated. Thanks!
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post #2 of 10 (permalink) Old Apr 19th, 2010, 4:57 am
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Hi Charles and it probably would not hurt to pull the ignition switch apart and give it a good clean. Measure the resistance on the contacts as I had to lightly file mine to improve what cleaning would not.
Give the kill switch a good clean and also would not hurt to disconnect the plugs from the above and give them a good treatment with de-oxit.
One of the bigger problems with bikes of some age is poor contacts in the electrical system so sytematically cleaning, and tightening etc will never hurt.

Regards,

Phil

Phil Mars

1984 K100RT
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post #3 of 10 (permalink) Old Apr 19th, 2010, 11:03 am Thread Starter
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Thank you for the feedback. I am hoping that the contacts on the ignition switch just need to be cleaned in order to resolve the issue, rather than needing to replace my Hall Effects Sensor.

Although I've never pulled my ignition switch off the bike (and I'm finding it rather difficult), I found a great write-up about the procedure. For future reference, it can be found here:

http://www.ibmwr.org/ktech/clean-ignition-switch.shtml
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post #4 of 10 (permalink) Old Apr 20th, 2010, 1:11 am
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Charles,

I would not look to the HES as that will cause problems such as rough running etc but should not stop it turning over. The best thing at this point is to clean all electrical connections and earths etc. After that it could be worth looking at the starter motor brushes as the load shed relay earths through the starter motor and that is a known cause of unusual problems but relatively easy to fix.

One way to test it is to rock the bike in gear and then try to start it. Also try starting with clutch in as opposed to being in neutral just to see if you can narrow the fault a bit.

How old is the battery?

Regards,

Phil Mars

1984 K100RT
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post #5 of 10 (permalink) Old Apr 20th, 2010, 10:11 am
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The headlight should be on before and after cranking but not during. That's what the load shed relay does. If that's not happening then that's where I'd start along with associated wiring. Kill switch is also good advice. Try not using the kill switch and see if probs go away for a while. If yes, then it looks like that's where to start.

The load shed relay works in a curious way using the electrical path through the starter brushes to work, so that could be another clue.



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post #6 of 10 (permalink) Old Apr 20th, 2010, 2:10 pm Thread Starter
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Thanks for all the input guys, I sincerely appreciate it. I'm still relatively new with the mechanical aspects of my bike, so I'm doing quite a bit of learning every time I need to take it apart to fix something.

So, FYI.... I had this problem happen again earlier today. I did a small but of riding, stopped to get some gas, and then when I tried to start it after filling up, the engine didn't try to turn. All I could hear was the fuel pump buzzing. I pushed the bike away from the pump, threw it in 3rd gear, and I was about to ask someone to push me so I could just pop the clutch and start it that way. I flipped the key back and forth (on/off) a handful of times, and then noticed that the headlight was working. I tried to start it again, and the engine turned no problem

Quote:
Originally Posted by phil_mars
I would not look to the HES as that will cause problems such as rough running etc but should not stop it turning over.
Correct me if I'm wrong... but if it was the HES, wouldn't it be a consistent problem? I'm still riding the bike, and this has happened 3 times total now (in about 200-300 miles of riding) but its an inconsistent problem. Most of the time it starts no problem, but every once in a while, the engine just doesn't want to turn

Quote:
Originally Posted by phil_mars
How old is the battery?
I bought the Battery from BMW towards the end of last years riding season, so it's a fairly new battery. I also gave it a full charge towards the beginning of this season.

Quote:
Originally Posted by voxmagna
The headlight should be on before and after cranking but not during.
Yes, and that is when I know that the engine won't try to turn (even before I try to start it). If I turn the key and the headlight is not on prior to starting, I know that the engine wont turn before I hit the ignition

I think you are all right in the idea the the problem is just an electrical connection issue. I just need to find the parts on the bike which need to be cleaned up, and then throw some dialectical grease on there.
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post #7 of 10 (permalink) Old Apr 20th, 2010, 6:47 pm
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loose or dirty battery cables (check both ends)...your getting enough amps for the dash lights but not the head lamp and starter....the one time it worked was probly luck...clean and tighten your cables and also load test your battery after a full charge...bet the problem is in your battery cables and or ground to frame. when you hit the kill switch and the head light went off is because it was getting most of its power from the alternator and not the battery....Or the battery even new is just trash.

Last edited by BAK04GT; Apr 20th, 2010 at 6:59 pm.
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post #8 of 10 (permalink) Old Apr 21st, 2010, 4:58 am
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Quote:
Correct me if I'm wrong... but if it was the HES, wouldn't it be a consistent problem? I'm still riding the bike, and this has happened 3 times total now (in about 200-300 miles of riding) but its an inconsistent problem. Most of the time it starts no problem, but every once in a while, the engine just doesn't want to turn
From what I have read but fortunately not experienced the HES can be bad all the time i.e. a consistent problem or only when it heats up but each time it is more a rough running rather than not turning over problem.

As mentioned well worth load testing the battery as one of the members of another forum has twice had the battery go bad over winter.

Not sure what the battery to earth lead is like on the later bikes but on my K100 it was a joke so I upped the size significantly in case it was impeding current flow.

If you have checked the ignition switch etc I would be leaning towards the starter brushes as they are not that hard to check and the manual gives the minimum measurement.

Regards,

Phil Mars

1984 K100RT
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post #9 of 10 (permalink) Old May 2nd, 2010, 5:42 pm Thread Starter
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So, my dad had an extra starter lying around, and is letting me borrow it for troubleshooting purposes.
He thinks the issue is just that the brushes on my starter are worn down, and need to be replaced.

So, I popped his starter in there and thus far... it seems to have solved the problem *fingers crossed* We'll see what happens. I'll follow up and let you guys know what the final solution is.

Last edited by charlesdonahue; May 3rd, 2010 at 9:53 am.
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post #10 of 10 (permalink) Old May 10th, 2010, 2:32 pm Thread Starter
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seems that was the starter was my problem. Haven't had the issue mentioned above since replacing it.
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