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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: daveson on January 06, 2019, 01:15:15 AM
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Hi team
I got me a new bike, '84 k100rt, 250,000km. after heaps of attempts i got it going about four times, first time about 2 minutes, the next two times about 1 minute, last time half a minute.
It seams to me a weak spark, even after i replaced the plugs,leads, and coils with known good ones.
Also replaced the petrol tank, pump, filter and injectors with known good ones.
Also tested and cleaned the starter.
My plan now is to replace the temp. relay and check temp. sensor which I'm not sure how to do. I'm planing this cause I'm wondering if the computer is getting a false overheat warning and therefore turning the engine off.
But this is just my random guess, if i knew the proper sequence to follow that would be my new plan.
Thanks heaps for any comments.
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Compression good
Usually runs for about two seconds, so spose starter system good
Sometimes it cranks continuously while starter is pressed, sometimes stops after a second or so.
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I wonder if you have a problem with the Hall Effect Sensors. I say this because their signal is needed to operate the fuel pump once the engine is running. You say the engine sometimes runs for two seconds. On the Jetronic ECU when the start button is pushed the pump is energized for two seconds, after the two seconds times out it's the Hall Effect Sensors that keep it running.
You might want to look up HES troubleshooting techniques.
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Silly question, but I got's to know. Is it a new or known fresh charged battery?
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I don't think there is an overheat feature that shuts down the engine, just the light. Start simple, clean all the ground cables you can find.
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fourepinn
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fourepinn
+1
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Battery question, all questions good because there is no mistake that I can't make. Battery good but not new and I've recharged after each of the occasions I've tried.
I'm using a '92 model tank so I bypassed the four pin with scotch locks
I hate to admit it but haven't cleaned the earth's yet, so that's first on the agenda.
Hall sensors, that's scary, but I'll read up, grit my teeth, and attempt it.
Am I right in calling this an early model rt,
as stated in workshop wiring diagrams, since it doesn't have k75 type seat and foot peg plates?
I know about the earth's under the tank but the diagram also shows another multi earth point but where is it on the bike?
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Ground point on engine is above the shifter on the left side of the intermediate section between the engine and the transmission. It's where the battery ground cable connects to the engine.
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Hey everybody
We fixed the bike
What I did and the results :
Taped up exposed hall sensor cable... No go
Cleaned hall sensor connections... No go
Replaced hall sensor... No go
Cleaned earth's... no go
Replaced fuel and temperature relays... No go
Replaced load shed and horn relays... no go
Replaced computer... She goes.
This bike had not been started in ten years
It now goes, is much cleaner, and I'm not afraid to tackle serious stuff like hall sensors any more.
Thanks all
That's one bike saved from the grave yard by motobrick. I wonder how many others have been.
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Thank you for the good report on your troubleshooting. Believe it or not, but feedback like yours is more valuable than whatever assistance we might offer. It's how the forum improves it's database.
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Congrats on the methodical, and successful result. Sure makes riding the brick that much more enjoyable, and something to talk about at rest points over a beer.
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Nicely done daveson! That took a lot of patience and perseverance, nice to know another K bike lives to be enjoyed! The experience of troubleshooting is priceless and the rewards great!
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When you have spare time have a play with the old ECU as can often resurrect by opening up and running a soldering iron over the electrical plug wires where they connect to the circuit board. Just flow small amount of solder on each wire when heating, often it's a dry joint from years of use/harness replugging etc.
Always nice to have a free spare in stock, you might be lucky!
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Good one, thanks, I'll look into it.