Starter cutting out. - K-Bikes.com - Excellence in Motion
 
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post #1 of 8 (permalink) Old Aug 16th, 2010, 4:44 pm Thread Starter
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Join Date: May 2010
Location: DC, ,
Posts: 157
Starter cutting out.

Hey all.

My 85 K100 is refusing to start again, its the same problem as before. Basically everything works when the start button is pressed, fuel pump pumps, but the starter spins for about a second then cuts off, then its starts spinning again for a second then cuts off. While holding down the start button the starter just turns on and off at a constant interval of about one second. I know the previous times this happened eventually the starter would stay on and the engine would fire up after i fiddled with everything. Bump starting doesn't work as well. I recently replaced the bushings in the starter so I know that's making good contact.

Something electrical it would seem... But i'm not sure what would cause the starter not to continuously run when the button is depressed or keep me from bump starting it. I'm going to check the spark and see if the plugs are wet when I get home but at work at the moment and was wondering if anyone had any ideas...

-Luke

------------------------------------------------------------------------------------
Current: 1985 K100RT Stripped.
See it here DC to Gaspe

Past: 1985 K100
See it here on my trip from DC to Panama
DC to Panama City
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post #2 of 8 (permalink) Old Aug 16th, 2010, 5:16 pm Thread Starter
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Think i found the problem as describe on K-tech...

http://www.ibmwr.org/ktech/starter-elec-probs.shtml

"In fact the ground is provided thru the ignition brain and on thru the Hall Effect Sensor!!!! That's why an intermittent HES problem causes on-off-on-off starter operation with the starter button held down."

Going to try and see if I can ground the starter relay ground to the chassis and get this bike home.

------------------------------------------------------------------------------------
Current: 1985 K100RT Stripped.
See it here DC to Gaspe

Past: 1985 K100
See it here on my trip from DC to Panama
DC to Panama City
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post #3 of 8 (permalink) Old Aug 16th, 2010, 9:18 pm Thread Starter
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Posts: 157
I spliced in a wire from the red/brown wire of the starter really to the battery negative. Starter ran like a champ, unfortunately it looks like the hall sensor is completely shot, or at least until it gets cold in DC.

You guys recommend getting a used one? Looks like the new ones are like 450 bucks.

------------------------------------------------------------------------------------
Current: 1985 K100RT Stripped.
See it here DC to Gaspe

Past: 1985 K100
See it here on my trip from DC to Panama
DC to Panama City
lukeman is offline  
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post #4 of 8 (permalink) Old Aug 17th, 2010, 8:07 am Thread Starter
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Has anyone rebuilt a hall sensor? I am seeing that from this article:

http://bmwmotorcycletech.info/Ignition.htm

That a Siemens part

http://www.bbautomacao.com/products.asp?cat=14 The BBHME56

is a replacement. Has anyone done this? Looks like the sensors are ~17 bucks a piece. Which is a lot cheaper than a new/old unit.

------------------------------------------------------------------------------------
Current: 1985 K100RT Stripped.
See it here DC to Gaspe

Past: 1985 K100
See it here on my trip from DC to Panama
DC to Panama City
lukeman is offline  
post #5 of 8 (permalink) Old Aug 17th, 2010, 8:43 am
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Location: Burton, British Columbia, Canada
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Well....thats from Snowbum,certainly one of the most knowledgeable gurus out there.I like reading him, sometimes too much info to sift through,but often funny. We have to replace the sensor on a Dodge Stealth.....hopefully we can find such alternatives because the OEM sensor is Mucho Dineros......!!!!!

I dont know if you have seen this....lots on testing all the electronic systems.
http://hrsbstaff.ednet.ns.ca/bvogel/...ont-start1.htm

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53

Last edited by H96669; Aug 17th, 2010 at 9:23 am.
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post #6 of 8 (permalink) Old Aug 17th, 2010, 10:52 am Thread Starter
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That's a good looking guide. I think i was using another one with the same information but not formatted as nicely.

I found this which may be of use to anyone else thinking of tackling a hall sensor rebuild.

http://advwisdom.hogranch.com/Wisdom...ll_sensors.pdf

Its for the oil heads, but its the same basic idea, and the K-bikes sensors are a hell of a lot easier to get at.

I bought a used one this morning to get the bike back home (95% sure this is the problem) and then also ordered the new sensors to rebuild the busted one. If that goes well I can swap in the rebuilt one and have the other as a backup.

It looks like the wiring harnesses are pretty suspect as well, poor insulation in a hot environment...

------------------------------------------------------------------------------------
Current: 1985 K100RT Stripped.
See it here DC to Gaspe

Past: 1985 K100
See it here on my trip from DC to Panama
DC to Panama City
lukeman is offline  
post #7 of 8 (permalink) Old Aug 22nd, 2010, 11:34 am Thread Starter
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Swapped out the hall sensor yesterday and it immediately fired to life. I was quite relieved...

I feel that I've crossed a milestone in wrenching on a K. Replacing a bad hall sensor.

The timing is a bit off now I think as the bike acts so much more mundane. The kick in the pants it used to have just isn't there at full throttle anymore. I marked everything but I need to tweak it some I suppose.

------------------------------------------------------------------------------------
Current: 1985 K100RT Stripped.
See it here DC to Gaspe

Past: 1985 K100
See it here on my trip from DC to Panama
DC to Panama City
lukeman is offline  
post #8 of 8 (permalink) Old Aug 23rd, 2010, 6:21 am
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I was reading a post on another forum a while ago which discussed timing a K and while I have not tried it on mine (if it ain't broke.....) but a mate of mine used to time his Morris minor the same way which essentially involved advancing the timing until it pings then back it off or adjusting it to give the best acceleration up a hill.

Every time I have removed my hall sensor I have just aligned the "V" mark and it seems ok but it does seem that getting the timing just right along with improved power also reduces vibration.

I would imagine replacing the sensors themselves is bound to make a slight adjustment just due to minute variations in the mounting or discrepancies in the individual sensors.

Phil Mars

1984 K100RT
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