Hi all, I am having an issue w/ my 1985 K100. I have installed a new fuel pump and the machine ran great. Then I had to install a new battery and that's when the issue started. When I would turn the ignition on and start the bike I could hear what what sounded like the fuel pump or something else (electrical) was running at a different pitch. Then the problem: like the bike was running out of fuel and stopped running. I would let it cool off and it would start and run for a little while then do the same thing. The battery I purchased was correct for the bike. If anyone has any answers for this problem I would greatly appreciate some input to narrow it down. Thank You

How long does it run before it stops?  Does it run okay when it is running, or is it stumbling and breaking up?  How long does it take to cool off?  Does the engine have to go back to room temperature? 

I am not sure what you are hearing, the only motors on the bike are the starter and the fuel pump.

In the past, the main cause of hot engine shutdown has been a bad Hall Effect Sensor.  These sensors are known to fail when the get hot and then start to work again when they cool off.  They not only control the spark, but also control injector timing.  There are threads here and on other forums describing ways to test and replace these devices. 

Trouble shooting usually involves either heating the sensors to cause them to stop working before the engine gets hot and/or shooting them with freeze spray to cool them off when the engine is still hot. 

Since you bike is one of the early models, it is quite possible that you have a bad ignition coil.  This is another common problem on the early models, and there is a failure mode that is temperature dependent so it would make sense with your symptoms.

Because of the coincidence of this problem with battery installation, check your battery terminal connections for tightness and your battery's transmission ground connection for a clean and tight connection before you do anything else.

What flasher relay do you have? Factory or Kisan Signal Minder?

Laitch wrote:Because of the coincidence of this problem with battery installation, check your battery terminal connections for tightness and your battery's transmission ground connection for a clean and tight connection before you do anything else.

Thank You, I'll check.