I have a 1987 K100 that I bought a couple years ago and up until now it has been trouble free.
I was out riding with some buddies a couple weeks ago and all was fine until the low fuel light came on. Which may or may not mean anything.  Soon after the bike started missing and eventually died on me. It sat a few minutes and then started and I made it a quarter mile before it died again. Same thing again. 
Luckily where it last died there was a guy out doing lawn work and he offered to trailer the bike home for me.
So it sat in the shop overnight and the next day it started right away. Ran for about 15 seconds and when it died the starter kicked in all by itself. Odd, eh?
So with work and whatnot I haven't had time to mess with it, but tonight when I got home I pulled the tank off to start cleaning electrical connections and grounds. And I discovered that sometime in the past someone decided that the fuel system didn't need a fuel filter.

So I'm sure I have some electrical gremlins and perhaps also clogged injectors from not having a fuel filter?

I am a newbie so if anyone can point me to the best place to start I would appreciate it.

Thanks in advance!

Dave

Hi Dave, 

You removed the tank to clean electrical connections and discovered it doesn't have a fuel filter. I hope your not aware that the filter is inside the tank, not under it, then this post might be helpful. If you are aware, you might think I've just told you to suck eggs, then sorry about that, but I dunno which way it is.  Since you have it for years without seeing a filter adds to my guess you expected it under the tank (and it hasn't been changed in years) Bricks are different in a lot of ways. The filter might be blocking.

Regards, Dave.

BadgerinNC wrote:So it sat in the shop overnight and the next day it started right away. Ran for about 15 seconds and when it died the starter kicked in all by itself. Odd, eh?

Dave

 Hi Dave,
If Daveyson is right, a new fuel filter will solve your problems. It is in the tank and needs to be replaced.

The starter running by itself (which it was doing when the bike was running I'd guess, you just didn't hear it) is a common problem with old or discharged batteries. The power drain of starting causes the starter relay contacts to fuse\weld together. It might be fixable (I've done it with a tap of a hammer to seperate them).  Search for tthe problem and fixes.

Ultimate fix is a new battery.

With the tank low on fuel, it's a good chance that any old dirt in the tank would get stirred up and sent to the filter to clog things up.

Remove the filler cap and take a good look inside. If there is anything that isn't fuel in there you should plan on getting it out. A new fuel filter goes in when you're done.

Charge the battery and clean the contacts in the starter relay. Then you should be good to go again.

Thanks for your input. I know there is supposed to be a fuel filter in the tank, but there isn't one. Just the screen under the pump.
The tank is fairly clean, a little surface rust in places, probably from the ethanol in the gas. So being this bike has been running since before i bought it without a fuel filter is there a chance the injectors are plugged?
I put in a new battery this year, the old one was too dead to take a charge. So I doubt the starter was stuck. And it started fine after that when I tried it.

Basically it is a process of elimination. Check all connections, check all grounds and maybe pull the injectors and give them a clean.
Any parts that tend to fail that might be the culprit?

I just don't want to be stranded in the mountains of western North Carolina. The chances of running across another kindly soul who would trailer my bike home are probably somewhere in the vicinity of slim to none.

Dave

BadgerinNC wrote:The chances of running across another kindly soul who would trailer my bike home are probably somewhere in the vicinity of slim to none.

Your chances seem to be far better than that based on your story.   First fail gets immediate help.  Only a negativist would believe that was unrepeatable. 

It's a process of elimination, alright. Are the plugs wet or dry after starting attempts fail? If they're dry, can you hear the fuel pump whining for a second or two after a starting attempt? If it isn't whining, replace fuse #6 and try again. If that starts the pump but not the engine, is fuel pumping from the hose attached to the rail? Don't light up yourself checking. 

Sounds like maybe blocked injectors and a stuck starter relay, but if you're confident the starter wasn't going the whole time, feel if the stater button is being pushed off by a spring when you release it. 

It's unlikely but some owners (like the previous owner of the bike in my avatar, as you can only just see) install a filter outside the tank.

Laitch wrote:

BadgerinNC wrote:The chances of running across another kindly soul who would trailer my bike home are probably somewhere in the vicinity of slim to none.

Your chances seem to be far better than that based on your story.   First fail gets immediate help.  Only a negativist would believe that was unrepeatable. 

it's one thing to happen upon someone 15 minutes away who used to live three houses down from me and have the same outcome when you are 150 miles away. No negative, just realistic.

The maddening thing is the bike would start and run fine in the shop. I guess I just don't trust it to keep running if I go any distance. There has to be something wrong and I would just as soon figure it out here than out in the middle of nowhere.

Is there some component on these bikes that would fail if it gets hot, causing the bike to start missing and die? And would be just fine once it cooled down?

I'll just keep poking around until I figure it out.

Hall sensors.

Try using a hot air gun on the Hall Effect Sensor cover plate,  coils or any electrical components that can fail intermittently due to heat.
Regards Martin.

The hall effect sensor is another item on my radar. I need to study up on testing it so I don't fry it if it isn't bad.

Tonight after work I decided to pull the ignition switch and give it a cleaning, I have read that a dirty switch could cause issues so i figured with the tank off now would be the time to do it.
I got the paint out of the setscrew hole, assuming the setscrew would be an allen screw. Of course it isn't and I didn't have a jewelers screwdriver so I found a suitable piece of metal and made one.
The switch was actually pretty clean. I polished everything up and was wondering what is the best grease to use before I reassemble.
Lots of opinions out there, everything from Vaseline to dielectric grease to TriFlow. 

What say ye?

If you have it, and you should, give the interior a quick shot of Deoxit. Besides being a corrosion remover Deoxit leaves a protective film that doesn't interfere with conductivity.

If you don't have that, get a pack of the gel that goes on light bulbs from the auto parts store and put a light film on all the parts.

Point-Seven-five wrote:If you have it, and you should, give the interior a quick shot of Deoxit. .

The Music Stop in Clemmons is liable to have some DeoxIT D5 hanging on their wall of stuff.

I know I had some Deoxit once upon a time. It may have vanished when I moved down here.
If I can't find it I will pick some up.

I'll try the Music Stop, I know they used some on my old Sansui to bring it back again. And they may have some interesting vinyl there too.

Found the DeoxIT 100, the DeoxIT Gold and an old can of Radio Shack contact cleaner. Surprised me, but I have the key switch sorted and back on the bike.

I took off the fuel rail and will be pulling the injectors to refurbish them.
But then I saw these on Ebay: 
https://www.ebay.com/itm/231974623891?_trkparms=aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20200818143230%26meid%3D8fc16e701c534630a84547b30eab39f7%26pid%3D101224%26rk%3D2%26rkt%3D5%26sd%3D254151923845%26itm%3D231974623891%26pmt%3D1%26noa%3D1%26pg%3D2047675%26algv%3DDefaultOrganic%26brand%3DMOSTPLUS&_trksid=p2047675.c101224.m-1

For the price it seems like a good deal. Anyone have experience with these or similar? Or should I just pick up a rebuild kit and stick with the Bosch?

I looked at the fleabay link, and am very interested in anyone experience, since I have a k75 that I know need injectors cleaned, at the very least!

See link post 10 https://www.k100-forum.com/t17104-k100-drivetrain-lookover#197570
Regards Martin.

I have a very lightly used set of those cheap injectors I will sell you for $25. They didn't work in my K100, but maybe will work in yours.

BadgerinNC wrote:For the price it seems like a good deal. Anyone have experience with these or similar? Or should I just pick up a rebuild kit and stick with the Bosch?

The ad copy description information states it has a single hole disc; the photos show it has a four-hole disc. This obvious discrepancy in the product's description calls into question everything about both the product and the seller. If it actually is a four-hole injector, they often seem to be reviewed as delivering less fuel economy and not necessarily delivering better performance, as Martin's link indicates.

Mr. Injector will service your injectors at a reasonable cost and has received many complimentary reviews from Brick riders in the USA.

For just the relatively cheap thrill of discovering whether your moto has a magical aura, Point-Seven-five's offer is the way to go.

Looks like I will pass on the cheapo injectors. And order a rebuild kit from Mr. Injector and give them a cleaning myself.

I have had great results with https://www.cruzinperformance.com/fuelinj.html
Their prices are very reasonable, $20 per injector and they replace o-rings, filter and pintle as needed.

I ended up buying a set of chinese injectors. They are single hole instead of the four hole ones. Once I get running again I will let everyone know how they perform.
 I also bought a new Hall Effect sensor. I got that in and am working on the injectors. 
Is there a trick for getting the old ones out? I was trying to get the front one out and I slid the whole front end of the bike over. 
Any tips would be appreciated.

This thread describes some technique and options. 

Point-Seven-five wrote:https://www.youtube.com/watch?v=nK8MqxEeMJY

That is perhaps a bit extreme. 
I think I will go the penetrating oil route.

I'm pretty sure it won't work because your bike doesn't weigh as much as the car. I only posted it as an example of desperate measures.

I haven't had much time to spend on my K100 as of late. last weekend was back to Wisconsin for a graduation party for my youngest son, he got his PhD in Material Science and will soon be off to the National lab at Los Alamos to work on things far beyond my comprehension. 

I had cleaned every electrical connection I could find, installed the fuel filter and this weekend I installed a new Hall sensor and the cheap chinese fuel injectors and it fired right up. After sitting for a while it smoked like a diesel but I'm hoping that will work itself out after I get on the road and warmed up.

No telling if this will solve my issue until I get some miles on it, but I'm hopeful.

Thanks for everyone's input, I am sure I will have plenty more questions in the future.

After feeling pretty good about the bike starting I was swapping the bike and the lawn mower to the garage so I could get the Volvo in the shop for new brakes and I noticed the last injector was leaking fuel from the fuel rail. I'm going to try swapping the o rings from the old injectors and see if that works. They look in pretty good shape. 

Oh well, it's always something. Actually, it's usually two things so i shouldn't feel too bad about just one.

I had the bike out for a long ride with three other guys from work yesterday. Ran pretty much flawless. No problem with getting the speedometer into three digits to keep up with the youngsters who think speed limit signs are suggestions.
The cheap injectors seem to work just fine. The problem was probably the Hall Effect sensor, but I may have just had a poor electrical connection somewhere.