1985 K100 Comprehesively Screwed

[k]

1985 K100 Runs rough. Sometimes won't start. Won't accelerate smoothly. When it runs, won't go past 4,000. Sometimes, it starts and runs smoothly, but is maybe down a little on power. Other times, it won't start, or it starts and runs rough. When it does start and run more or less fine, if you turn it off and restart it, it may run like crap.

Mechanic can't figure it out. Fuel pump fine and swapped to verify. Plug wires have good resistance. Plugs good. His solution is for me to replace every part on the bike with factory BMW parts, then see what the problem is. That's nuts. This bike ran fine, last year, and I don't need a factory BMW fuel pump.

Haven't ridden it at all this year because the thing won't run. Tired of throwing good money after bad with this bike.

[Chaos]

Have you read through the repair guidance directory here?  Sounds electrical and I'm sure the mechanic was just trying to get you to go away.  Best get your hands greasy.

[Filmcamera]

Sounds like something similar I had happen to me, turns out it was a fault in the loom to one of the injectors so sometimes it would fire and sometimes it would not.

[k]

Sounds like something similar I had happen to me, turns out it was a fault in the loom to one of the injectors so sometimes it would fire and sometimes it would not.

Interesting. That would certainly do it.

[Motorhobo]

Are they the original plug wires? How do you know the sheathing on one of them isn't faulty causing the spark to arc to the block rather than ignite the fuel in the cylinder? If that's happening, it might only be happening under certain conditions and that might not be detectable just by measuring resistance.

If I were in your shoes, I'd put new or proven good wires in and try again, or toss a blanket over the headlight, run the bike in the dark and look for arcing at the plugs. If those are the original wires, I'd replace them. I don't think there are many K-bikes out there still running on those original brass wires when you can get good replacements for $60. Even BMW has started selling silicon replacements for those overpriced brass honkers.

[k]

I installed a set of the Ramshox/Realm Engineering plug wires, last year.

Mechanic says I should throw those out and put a new set of solid original factory wires back on.

[Motorhobo]

Sounds like what your really need is a new mechanic, or better yet, a manual and some tools. You could rent a garage for a year for what that mechanic is liable to charge you to fix this bike. You're much much better off doing it yourself. Lots of very experienced brains to pick here, much better brains than mine.

[Motorhobo]

Sounds like what your really need is a new mechanic, or better yet, a manual and some tools. You could rent a garage for a year for what that mechanic is liable to charge you to fix this bike. You're much much better off doing it yourself. Lots of very experienced brains to pick here, much better brains than mine.

On a more helpful note -- it doesn't sound like spending +$200 on a new set of OEM brass wires is going to help. Most of the people on this forum are running aftermarket plugs with no issues. It sounds to me like you're not firing all your cylinders. If it were me, I'd

1) Pull the plug out of the ICU under the tank and spray it with contact cleaner, then plug it back in.
2) Pull the plug that goes to the tank and spray it with contact cleaner.
3)  Start the bike cold and run it till this issue appears, then shut it off and immediately pull each of the plugs and find out which one is wet with fuel.

That's what I'd do, but then again, I'm not the smartest one here so maybe you'll get lucky and someone else will chime in.

[Motorhobo]

1) Pull the plug out of the ICU under the tank and spray it with contact cleaner, then plug it back in.

Actually, I mean the ECU under the seat, not the tank...

[k]

Actually, I mean the ECU under the seat, not the tank...

Already did that and swapped it with a spare. Same issue.

[Chaos]

Just a wild ass guess, but I had a sporadic bad running issue that turned out to be water settling in the bottom of the gas tank.  Got that jewel either here or over on BMWMOA.  The water stays there even with fresh gas, and once there's enough it gets picked up by the pump. Couple cans of HEET gas dryer took care of it.  Some Techron probably wouldn't hurt either.

[k]

Just a wild ass guess, but I had a sporadic bad running issue that turned out to be water settling in the bottom of the gas tank.  Got that jewel either here or over on BMWMOA.  The water stays there even with fresh gas, and once there's enough it gets picked up by the pump. Couple cans of HEET gas dryer took care of it.  Some Techron probably wouldn't hurt either.

In case it was that, I did drop a bottle of HEET down there. Same issue.

Maybe I'll dump another bottle down there.

[Laitch]

At this point in the program, it might help if you listed every part and procedure that has been done to your bike since you've owned it.

Rough running can come from intake leaks. What have you done to check for those?
It can come from failing coils or faulty coil connections. Have you checked those?
Incorrect valve clearances and unsynched throttle bodies won't help.
Faulty ground connections are culprits.
Decrepit fuel filters are culprits.
Clogged fuel lines, fuel filters and fuel injectors are culprits.

The least expensive option is to take an orderly approach to investigation. Check for throttle body manifold intake leaks. Check for a leaking z-hose connecting the air box to the crankcase. Look for corrosion in the coil terminals for the plug wires. Keep track of which wire goes where when you do that. Is the fuel tank clean? Does the fuel filter have a date on it? Check the valve clearances. There is much you can do before financing the well-being of a BMW service department—or any mechanic, for that matter. Instructive materials are found on this site and others. As has been indicated, the Repair Guidance section is full of lore.

Back in November 2016 you wrote,
K1100, K1200, ST1100-1300, FJR, Goldwing, maybe the Guzzi Norge. I just don't know if it's worth it to make a jump.

By now, the worth of that jump distance might be more clear but most used bikes will need work of some sort anyway.

[k]

At this point in the program, it might help if you listed every part and procedure that has been done to your bike since you've owned it.

Rough running can come from intake leaks. What have you done to check for those?

Not sure. Which intake?


It can come from failing coils or faulty coil connections. Have you checked those?

Connections look sound. Don't coils just work, or not? Is there a degradation phase? Sometimes, the bike will run somewhat fine, for a bit. 'Spose I could swap them.

Incorrect valve clearances and unsynched throttle bodies won't help.

Had valves and throttle bodies done last year.


Faulty ground connections are culprits.

Makes sense. Which ground should i chase?

Decrepit fuel filters are culprits.

Fresh fuel filter.

Clogged fuel lines, fuel filters and fuel injectors are culprits.

Fuel lines are new. Fresh fuel injectors, last year. Tank cleaned.

The least expensive option is to take an orderly approach to investigation. Check for throttle body manifold intake leaks. Check for a leaking z-hose connecting the air box to the crankcase. Look for corrosion in the coil terminals for the plug wires. Keep track of which wire goes where when you do that. Is the fuel tank clean? Does the fuel filter have a date on it? Check the valve clearances. There is much you can do before financing the well-being of a BMW service department—or any mechanic, for that matter. Instructive materials are found on this site and others. As has been indicated, the Repair Guidance section is full of lore.

Back in November 2016 you wrote,
K1100, K1200, ST1100-1300, FJR, Goldwing, maybe the Guzzi Norge. I just don't know if it's worth it to make a jump.

By now, the worth of that jump distance might be more clear but most used bikes will need work of some sort anyway.

Usually, a system will give a clear idea what the problem is. This bike has stumped a BMW professional.

Thanks for the advice. I need to find time to dig into it.

I'm now having a blast on a Harley. I work and have an active life. I don't have much time, any more, to play mechanic.

[Laitch]

I'm now having a blast on a Harley.

That's more like it. Enjoy life. Use the site to sell the K.

[k]

That's more like it. Enjoy life. Use the site to sell the K.

I get that, but I have a hard time not solving a challenge. Plus, this bike was good to me for a lot of years.

[Laitch]

. . . this bike was good to me for a lot of years.

Be grateful for that, then sell it.

[Motorhobo]

I get that, but I have a hard time not solving a challenge. Plus, this bike was good to me for a lot of years.

Sounds like a conundrum - if you want to the challenge then you have to solve it without help of a mechanic, otherwise you'll have to sell that Harley to pay the mechanic to solve the challenge presented by the bike you don't want to take the time to fix.

There are three possibilities: air, fuel and spark. You didn't mention whether your z-hose was replaced. That is often the problem and you won't see it without pulling the hose and looking at it, and even then there might be micro cracks that you wouldn't think would cause a problem. I just put a brand new on on even though the old one didn't look 'that bad' and noticed an improvement. You said the throttle bodies had been done, but didn't mention whether all the rubber boots on them were replaced. I once had a cracked throttle body boot that caused crappy running, and detected it by pointing the MAP gas nozzle at it.

Anyway, the problem with BMW mechanics is that many of them really don't understand these older K-bikes. They weren't trained on them. They were trained on the plug and play component engineering of the newer BMW generation. You're bound to find more old school wrenches who can actually problem solve and diagnose K-bike issues here than in a BMW dealership.

Just sayin. Anyway, it ain't going away so enjoy the riding season and come back to it when you have some time. Otherwise, you can sell it for a song and get it out of the garage, like Laitch suggests.

[Laitch]

Usually, a system will give a clear idea what the problem is.

If that were the case, life would be much less complex than it is—starting with interpersonal relationship systems. :giggles

You've stated you don't have time to "play mechanic". I believe you based on your answers to my queries. It will take not only your time to learn mechanical aptitude but also the time of those attempting to teach you. If your heart were into it, you'd make the time. Why bother though when you're enjoying life as it is.

It's not as though learning to repair your K-bike will make you a better person.

[Motorhobo]

It's not as though learning to repair your K-bike will make you a better person.

Not to belabour the point, but there's no doubt that learning to repair my K-bike made me a better person. What I gained in terms of expanding my horizons, understanding of things mechanical, and using cognitive assets to solve new problems were priceless.  Maybe that doesn't make me a 'better' person but I'm definitely a more well-rounded one who feels comfortable interacting with a much wider range of people.

[The Mighty Gryphon]

Learning how my bricks work, how to keep them working, and how to make them work when they don't has given me incredible amounts of inner peace, especially late in the day when traveling on desolate stretches of road far from home.

[k]

Weird. Tonight, I hit the button, and it idled smoothly for over ten seconds, then it started struggling, slowing down.

 I may drain the tank just to see if that does anything.

[beemuker]

Weird. Tonight, I hit the button, and it idled smoothly for over ten seconds, then it started struggling, slowing down.

 I may drain the tank just to see if that does anything.

It won’t. Will not run without fuel. Sorry you are having this issue. I am on my 3rd 75 and have not had any big problems. My outboard was malfunctioning, and after going through a lot of headache, finally discovered that it was a bad plug, even though it looked pretty new and had spark. Hope you discover your issue and it is an easy fix.

[k]

It won’t. Will not run without fuel.

???

Obviously, I'll refill it with fresh gas.

[Laitch]

I may drain the tank just to see if that does anything.

Is there any residue in the tank—black particles, varnish flakes? Are the fuel pump wires tightly connected to the pump? Is the black vibration damper surrounding the pump in its holder in good shape—not soft, and holding the pump firmly. Is the arrow on the fuel filter pointing toward the tank's floor rather than toward the pump? Are all fuel hoses tightly clamped to their connections? You'll need to remove the four screws holding the fuel tank cap assembly then remove the assembly to have the best view.