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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: Atabeach on June 27, 2026, 02:23:55 PM

Title: 85 K100 ...all of a sudden backfiring and stalling when HOT!
Post by: Atabeach on June 27, 2026, 02:23:55 PM

Ok was running absolutely perfect, yesterday...she always backfired under deceleration but now on low rpm throttle. Starts right up, soon as the temps get up backfiring & stalling on low RPM.  OK soooo I used the propane trick to check for leaks at the throttle bodies...no noticeable increase in RPM. Pressed the starter button, verrrry slight decrease in RPM. The fuel pump is new , Z hose new...checked for leaks in and around air box... next Im going to take out plugs and see how they look. any usual suspects Im missing? TIA
 

Title: Re: 85 K100 ...all of a sudden backfiring and stalling when HOT!
Post by: Laitch on June 27, 2026, 04:56:38 PM

Verify that the battery positive clamp, the battery ground clamp and the battery ground cable attachment on the transmission are tight.

Click this link (https://motobrick.com/index.php?topic=11014.msg95717#msg95717) to the opening post of the Service Manual section here. Click on the link to Vogel's troubleshooting guide at the bottom of the opening post. Perform the tests of the throttle switch and the coolant temperature sensor explained on pp. 21–22. Let us know the results.