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1Back to top Go down    No-Start Issue on Tue Jun 07, 2016 10:53 pm

Bikesmith

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Hey Friends!
I have a new puzzler making me scratch my head and I'm hoping you can help.
My 1985 K100RS began having intermittent trouble starting that is no longer intermittent. When I turn on the ignition, everything is normal. All the usual lights and such. When I press the starter button, the starter does nothing. The fuel pump comes on while I push the starter switch, so I don't suspect a problem in the starter switch. But the fuel pump doesn't stay on for 1.5 seconds as usual. It's only on while the starter switch is pressed.
I would suspect the starter itself, except that I noticed that the load shedding relay isn't switching. The headlight stays on while I push the starter.
So I suspected the starter relay, especially since I was starting the bike with a barely functional battery for a while (That issue is resolved. New battery and voltage regulator). So I got a new starter relay and pulled apart the old one. I saw that the points were fried in the old one which I felt confirmed my guess. I cleaned up the points on the old relay to keep it as a spare.
I just tried putting in the new relay and it made no difference at all. The reconditioned old one didn't work either. I've tried tracing this through on the wiring diagram and looking at the no-start troubleshooting page, but I'm afraid this one might be beyond me.
Any ideas?


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Jon
Mechanically competent, electrically idiotic
------------------------------------
1985 BMW K100rs
1940 Royal Enfield WD/CO
1968 Honda CL125
    

2Back to top Go down    Re: No-Start Issue on Tue Jun 07, 2016 11:09 pm

RicK G

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Can you hear the relay clicking in? If you can then check to see if there is 12v at the terminal which goes to the starter motor when you push the start button.


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If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

3Back to top Go down    Re: No-Start Issue on Wed Jun 08, 2016 6:42 am

Dai

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If the relay clicks it's possible that you've connected the two red cables the wrong way round. The battery should go to the screw tab on the right (marked 30) and the starter motor to the screw tab on the left (marked 87).


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'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

4Back to top Go down    Re: No-Start Issue on Wed Jun 08, 2016 11:17 am

Bikesmith

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Okay, I have some additional info:

  • The starter relay is not clicking
  • There is power to pin 30
  • There is no power at pin 87 at any time
  • The fuel pump relay is clicking
  • Load shed relay is not doing anything, headlight stays on (no surprise there, since there's no output from the starter relay)
  • There is continuity from pin 11 at the ICU pin 85 of the starter relay.
  • There's 11.8 volts measured from the positive terminal of the battery to pin 85 anytime the ignition is on, no change when the starter switch is pressed
  • There's 846 ohms from pin 85 to ground when ignition is on, changes to 850 while the starter switch is pressed
  • There's 6.9 volts going to pin 86 on the starter relay when the starter switch is pressed.


That last point seems the most suspicious to me. That should be 12 volts, right? After work tonight, I'll take apart the switch and clean the contacts. It would be fantastic if that was my only problem.

Does the behavior of the ICU seem correct? Does it just always provide ground on pin 11? Does it change under some circumstances? Is that resistance a problem? The low voltage? I guess it just needs to provide enough ground to trip the relay, right?

Thanks for your help, friends.
-Jon


__________________________________________________
Jon
Mechanically competent, electrically idiotic
------------------------------------
1985 BMW K100rs
1940 Royal Enfield WD/CO
1968 Honda CL125
    

5Back to top Go down    Re: No-Start Issue on Wed Jun 08, 2016 12:40 pm

duck

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@Dai wrote:If the relay clicks it's possible that you've connected the two red cables the wrong way round. The battery should go to the screw tab on the right (marked 30) and the starter motor to the screw tab on the left (marked 87).

All a relay does is complete an electrical connection. Which direction the electrons flow shouldn't matter.


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Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S
14 Yamaha WR250R
http://www.ClassicKBikes.com
    

6Back to top Go down    Re: No-Start Issue on Wed Jun 08, 2016 4:16 pm

Dai

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I agree. What the hll was I thinking of...


__________________________________________________
'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

7Back to top Go down    Re: No-Start Issue on Wed Jun 08, 2016 7:14 pm

robmack

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@Bikesmith wrote:That last point seems the most suspicious to me. That should be 12 volts, right? After work tonight, I'll take apart the switch and clean the contacts. It would be fantastic if that was my only problem.
There is some resistance in the circuit across which voltage is being dropped. That could be the start switch. One way to prove it is to measure the voltage across the switch contacts. It should be close to 0 volts when pressed and 12V when open.

@Bikesmith wrote:Does the behavior of the ICU seem correct?
What behaviour is that?

@Bikesmith wrote:Does it just always provide ground on pin 11? Does it change under some circumstances?
It provides continuity to ground until the engine RPMs rise above 700, at which time it removes the connection to ground. The reason for this behaviour is to prevent the starter motor from being engaged by the start switch when the engine is running.

@Bikesmith wrote:Is that resistance a problem? The low voltage? I guess it just needs to provide enough ground to trip the relay, right?
Correct. The voltage is below the pull-in voltage of the relay. It has to be around 10.5V or more.


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Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

8Back to top Go down    Re: No-Start Issue on Fri Jun 10, 2016 5:03 pm

Bikesmith

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Hey Everybody,
I fixed it! It was the ignition switch. I realized when I noticed that my dashboard lights were really dim that my problem was further "upstream" in the electrical system than I'd been thinking.
I rebuilt the ignition switch and it was like magic. Not only did I fix the starting problem, but everything is better. The dashboard lights are brighter than they've ever been. The bike starts better than ever. It's fantastic!
Yay!
-Jon


__________________________________________________
Jon
Mechanically competent, electrically idiotic
------------------------------------
1985 BMW K100rs
1940 Royal Enfield WD/CO
1968 Honda CL125
    

9Back to top Go down    Re: No-Start Issue on Fri Jun 10, 2016 6:59 pm

Brad-Man

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Excellent news and thanks for posting your fix.

Karma point to you even though the forum doesn't have them


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Toys don't make the man - Man makes the toys....
    

10Back to top Go down    Re: No-Start Issue on Fri Jun 10, 2016 10:35 pm

RicK G

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Jon while I think of this, it is best for the future life of the ignition and handlebar switches to put relays in the headlight circuits because it dramaticly lowers the current carried by those switches to about 2% of what they now carry.
If you search the forum for Eastern Beaver relay you will find how to do it or you may already know but either way it is a good thing to do and it even gives you much better lights.


__________________________________________________
If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

11Back to top Go down    Re: No-Start Issue on Sat Jun 11, 2016 1:13 pm

Bikesmith

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Great suggestion, Rick! Thanks!
In the time I've been addressing all the problems on this bike I've also been doing upgrades and making changes to improve reliability. I've already replaced the stock radiator fan with a Spal. Since I live at 5400 feet elevation and will take the bike above 14000 feet but also down to sea level, I replaced the altitude correction plug with a dashboard switch.
So, yeah, I'm definitely going to wire in a headlight relay.

Does anybody else have any suggestions for changes to improve reliability or usability on our bikes?

In one of Chris Harris' videos, he suggests that putting a plug into the end of the drive shaft would keep grease from migrating into it from the final drive splines, lengthening the service interval. Has anyone tried that? Does it work?

Thanks as always for all your help, friends.
-Jon


__________________________________________________
Jon
Mechanically competent, electrically idiotic
------------------------------------
1985 BMW K100rs
1940 Royal Enfield WD/CO
1968 Honda CL125
    

12Back to top Go down    Re: No-Start Issue on Sat Jun 11, 2016 8:29 pm

RicK G

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It is a good move to plug the shaft but it's not a critical as many think because the shaft does not move very much on the splines, about 0.1mm if that. The right lubricant and regular servicing is far more important.


__________________________________________________
If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

13Back to top Go down    Re: No-Start Issue on Sun Jun 12, 2016 2:30 pm

Kyle10

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@Bikesmith wrote:Does anybody else have any suggestions for changes to improve reliability or usability on our bikes?

Engine to battery, positive cable to starter and ground cables. Upgrade them. Easy, effective.

Great kit, great vendor


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1985 K100rt 0052183
1983 Honda VF750 007713
    

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