FJowners.com

General Category => Maintenance => Topic started by: Jester on July 19, 2010, 05:03:12 PM

Title: lumpy at low revs
Post by: Jester on July 19, 2010, 05:03:12 PM
Hi, I am borrowing an 84 fj1100 of a friend at the moment as my CB750 is a hateful piece of garbage and I may be buying it of him but it has a couple of small issues. The main one is it runs very lumpy at low revs and doesn't seem to be firing on all pots, when the revs are higher (about 4-5k) it runs like a dream, any ideas what could cause this? If it's an easy fix I could very well buy it off him, they are just so comfortable and comfortless to ride.

Thanks in advance for any suggestions you guys or girls have.
Title: Re: lumpy at low revs
Post by: racerman_27410 on July 19, 2010, 05:08:01 PM
many times a thorough carb cleaning is all the carbs need to be made to run great again.

David R has a great writeup on doing just that and tuning the carbs properly afterwards.

http://www.fjowners.com/index.php?topic=655.0 (http://www.fjowners.com/index.php?topic=655.0)


Kookaloo!

Frank
Title: Re: lumpy at low revs
Post by: Jester on July 19, 2010, 05:53:34 PM
Thanks for the very quick response, looks like I've got something to do in the garage tomorrow, which is cool as it's forecast for rain most of the day :good2:
Title: Re: lumpy at low revs
Post by: racerman_27410 on July 19, 2010, 07:26:11 PM
Quote from: Jester on July 19, 2010, 05:53:34 PM
Thanks for the very quick response, looks like I've got something to do in the garage tomorrow, which is cool as it's forecast for rain most of the day :good2:


take your time and have fun !   the bike will reward you for it  :good2:


Kookaloo!
Title: Re: lumpy at low revs
Post by: CPTKEB on September 20, 2010, 02:13:28 PM
Check the boots on the spark plug wires.  Sometimes they vibrate and unscrew from the wires.  I always "preload" mine by installing them with pressure that makes them want to tighten instead of loosen.  The resistors in them maybe bad as well.
Title: Re: lumpy at low revs
Post by: SlowOldGuy on September 20, 2010, 02:49:36 PM
Sounds like clogged idle jets.  If you bump the idle jets to 40s, they don't clog as easily.

DavidR