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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: zipster68 on July 17, 2019, 04:30:06 PM

Title: bucks, runs on maybe 2 cylinders and then back to normal
Post by: zipster68 on July 17, 2019, 04:30:06 PM

Hi Brickers,
I've got a new (intermittent) problem on my 86 K100.  Bike starts easy, idles great and after maybe 10-15 minutes bucks a couple times and acts like it's running on 2 cylinders, for maybe 15 seconds (doesn't stall out).  Then runs perfectly normal.  This has happened maybe 3 times.  Doesn't appear related to wetness, temperature.  I've got fresh gas in there and the tank looks clean.  I've got a very new looking coil pack that I've swapped in a couple years ago.
Possible issues...
fuel filter
injectors
throttle pos'n sensor
Looking for suggestions if you've got any.
Cheers,
Ray

Title: Re: bucks, runs on maybe 2 cylinders and then back to normal
Post by: natalena on July 17, 2019, 04:44:52 PM

You left out the 4-pin ;)
If it runs great after the sporadic episodes, I'd be guessing electrical.

Title: Re: bucks, runs on maybe 2 cylinders and then back to normal
Post by: Laitch on July 17, 2019, 05:05:07 PM

Check and clean the four-pin pump connector.
Check all the interior fuel lines for clamp tightness.
Clean and tighten the battery negative ground on the transmission.
Check the battery connections for tightness.
Check the ground connections on the backbone frame member under the tank.
Change the fuel filter if you don't know how old it is, or if it's a Fram filter.

There's more after this. :giggles

Title: Re: bucks, runs on maybe 2 cylinders and then back to normal
Post by: daveson on July 17, 2019, 08:50:40 PM

Temporary wonky on two cylinders, maybe check coil connections.

Title: Re: bucks, runs on maybe 2 cylinders and then back to normal
Post by: zipster68 on July 17, 2019, 09:35:46 PM

Don at Detroit BMW says water in the gas and/or tank.  My cap is installed backwards and that isn't good either for water.  I'm gonna pump all of that gas out, mop the bottom and start fresh. 

Title: Re: bucks, runs on maybe 2 cylinders and then back to normal
Post by: Scott_ on July 17, 2019, 09:48:02 PM

Don't forget to check/clean the multi-pin plug on the ignition control module..

Title: Re: bucks, runs on maybe 2 cylinders and then back to normal
Post by: zipster68 on July 18, 2019, 09:23:32 AM

I'll check it.  Where the hell is it?
-Ray

Title: Re: bucks, runs on maybe 2 cylinders and then back to normal
Post by: Laitch on July 18, 2019, 12:48:54 PM

Ignition control unit is at the left arrow; its plug is at the right arrow.
(http://www.motobrick.com/gallery/2/1601-180719124742.png)