'86 K100RS- Strangest Problem- at wits end.. Help

flipshide · 07-05-2012, 03:52 PM

Having the strangest issue right now with the bike. It started off when riding. The bike would get going just fine and appeared to be running normally when, out of the blue, it would cut out and die. I talked to a local BMW mechanic and he suggested it may be the fuel filter. I went into the gas tank and replaced the filter and the issue continues. The throttle seems to be working properly, but as the bike gets going it starts to cut out when shifting through gears. Once I stop rolling and give it a few seconds, it fires right back up, will go a bit and does it again.

The battery is new this season and is showing good charge. Anyone else experience this before or know other things I could cross off the list before I take it in. Can't afford to spend too much money chasing ghosts. I hope I can get some good leads.

Dodsfall · 07-06-2012, 07:30 AM

It sounds like it might be starving for fuel. You eliminated the fuel filter as an issue, but there are another couple of items that can cause the same symptoms.

Fuel tank not venting:
This is easy to test for. When the motorcycle quits, simply open the gas cap and see if it will start. The fuel tank must allow air in to replace the used fuel or a vacuum will build up and stop or slow the fuel flow.

Fuel pump failing:
The fuel pump may not be putting out the volume of fuel needed to keep the motorcycle running, or it may only work intermittently.

Clogged injectors:
The fuel injectors or fuel line may be restricting the fuel flow.

owrstrich · 07-22-2012, 12:55 PM

greetings flipshide...

hows abouts an update... was the hes...

j o

daver80 · 08-02-2012, 05:01 PM

flipside- I have an 86 R80 (airhead) when I first owned it in 1994, it had a similar problem. Just cut out. then would restart. My solution turned out to be the ignition switch. Replaced it and Havent had the same problem since. Dave

DavidBMWRT · 09-25-2012, 07:05 AM

I had a similar problem that turned out to be a broken wire. As the bike heated up the wires would separate. Broken wires are difficult to locate. A wiring harness cost about $200 and takes about 4 hours to replace but it may be a sure fix.
I wonder how many great motorcycles have been trashed because of a broken wire?

spudbike · 11-22-2012, 09:31 AM

Could be the grounding not a good contact.

BoxerBamR100 · 11-22-2012, 10:49 AM

A friend of mine is having the same problem--it's his clutch safety sensor. He has one of those clutch levers with a "speed adjust" that tightens/loosens the clutch tension about 1/4 inch per turn. We switched that to its tightest setting, and tightened the cable adjuster at the hand lever--that was loose-- and the problem went away for about a week then returned. I suspect that the cable just needs to be tightened up on both ends or it's stretched out and it can't engage the clutch sensor, so it's shutting the engine off for safety--as it's designed to. I hope this helps. Let us know how its coming.

DavidBMWRT · 12-10-2012, 06:29 PM

Did you fix the bike?

07-05-2012, 03:52 PM	#1
flipshide Newbie Join Date: Jul 2012 Posts: 6	'86 K100RS- Strangest Problem- at wits end.. Help Having the strangest issue right now with the bike. It started off when riding. The bike would get going just fine and appeared to be running normally when, out of the blue, it would cut out and die. I talked to a local BMW mechanic and he suggested it may be the fuel filter. I went into the gas tank and replaced the filter and the issue continues. The throttle seems to be working properly, but as the bike gets going it starts to cut out when shifting through gears. Once I stop rolling and give it a few seconds, it fires right back up, will go a bit and does it again. The battery is new this season and is showing good charge. Anyone else experience this before or know other things I could cross off the list before I take it in. Can't afford to spend too much money chasing ghosts. I hope I can get some good leads.

07-06-2012, 07:30 AM	#2
Dodsfall Administrator Join Date: May 2008 Location: Illinois, USA Posts: 16,356	It sounds like it might be starving for fuel. You eliminated the fuel filter as an issue, but there are another couple of items that can cause the same symptoms. Fuel tank not venting: This is easy to test for. When the motorcycle quits, simply open the gas cap and see if it will start. The fuel tank must allow air in to replace the used fuel or a vacuum will build up and stop or slow the fuel flow. Fuel pump failing: The fuel pump may not be putting out the volume of fuel needed to keep the motorcycle running, or it may only work intermittently. Clogged injectors: The fuel injectors or fuel line may be restricting the fuel flow. __________________ 2008 XL1200R To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

08-02-2012, 05:01 PM	#4
daver80 Motorcyclist Join Date: Jul 2009 Posts: 13	cutting out flipside- I have an 86 R80 (airhead) when I first owned it in 1994, it had a similar problem. Just cut out. then would restart. My solution turned out to be the ignition switch. Replaced it and Havent had the same problem since. Dave

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07-22-2012, 12:55 PM	#3
owrstrich Newbie Join Date: Sep 2009 Location: CA OR WA ID WI IN Posts: 6	greetings flipshide... hows abouts an update... was the hes... j o

09-25-2012, 07:05 AM	#5
DavidBMWRT Verified Join Date: Jan 2009 Posts: 20	I had a similar problem that turned out to be a broken wire. As the bike heated up the wires would separate. Broken wires are difficult to locate. A wiring harness cost about $200 and takes about 4 hours to replace but it may be a sure fix. I wonder how many great motorcycles have been trashed because of a broken wire?

11-22-2012, 09:31 AM	#6
spudbike Verified Join Date: Sep 2010 Location: Caldwell Idaho Posts: 42	Could be the grounding not a good contact.

11-22-2012, 10:49 AM	#7
BoxerBamR100 Verified Join Date: Oct 2012 Location: Houston, Tx Posts: 15	A friend of mine is having the same problem--it's his clutch safety sensor. He has one of those clutch levers with a "speed adjust" that tightens/loosens the clutch tension about 1/4 inch per turn. We switched that to its tightest setting, and tightened the cable adjuster at the hand lever--that was loose-- and the problem went away for about a week then returned. I suspect that the cable just needs to be tightened up on both ends or it's stretched out and it can't engage the clutch sensor, so it's shutting the engine off for safety--as it's designed to. I hope this helps. Let us know how its coming.

12-10-2012, 06:29 PM	#8
DavidBMWRT Verified Join Date: Jan 2009 Posts: 20	Did you fix the bike?