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Thread: Engine Surging/Hunting 2-3 rpm (again)

  1. #1
    Hi guys, I've read through the forum and seen this issue has had lots of coverage already.
    I'm a Buell newbie (and trying to keep heart with such a potentially awesome machine) - and not much of a mechanic either.

    The issue: engine surges/hunts especially at 2-3,000 rpm at small or steady throttle openings (much smoother when opened wide/accelerating hard or above 3,000 rpm) - so makes slow town riding or steady traffic around 20-35mph uncomfortable and takes the shine off such an awesome machine.

    My new beast is a xb12x 2008 with Thunderstorm engine, stock exhaust (for now) and 9,000 miles.

    Just had it given a full service by a backstreet indie Buell mechanic, so new plugs, HT leads, engine + transmission oil + filter in the service, but didn't have software for ecm or tps checks. Improved the condition a lot, but not completely.

    From the forum, I see there are a number of possible issues/cures still to explore:

    1.TPS reset
    2. ECM remap
    3. Tighten grounding wires
    4. Breather Mod
    5. Possible oil in the breather element (from over filled oil)
    6. Exhaust valve malfunction
    7. Any other suggestions???

    Are any of these easy/best to try first as a newbie and unsure mechanic? - Or should I just keep throwing my hard earned cash at the backstreet guy or pay top whack for a Buell friendly HD dealer, bearing in mind the cost of working through all those issues...

    Also, should I sort this issue before upgrading exhaust, or is the excuse of a new exhaust also a possible cure?

  2. #2
    Senior Member
    Join Date
    Sep 2010
    1 - probably not going to be your answer
    2 - shouldn't need it since you have the stock exhaust
    3 - should always make sure they are tight
    4 - try it, people have had good and bad experiences
    5 - maybe
    6 - zip tie the wire so it stays open, it won't hurt your ride but it will give you a better idea of what's going on
    7 - try those first, maybe dirty injectors? Maybe even a slow intake leak under pressure.

    Don't try throwing new parts at it while you already have a problem, you'll just confuse yourself and those that are trying to help you.

  3. #3
    Really helpful. Thank you! - I can certainly track down the ground points, then I'll see what I can figure myself and take it from there.

  4. #4
    Senior Member lunaticfringe's Avatar
    Join Date
    Feb 2011
    AmishLand, PA.
    fastmart: wolfo's info is always excellent. though my uly is a 2007 with different ecm and dfi system i found that the surging and hunting and pecking in the rmp range you mentioned was so incredibly annoying i was going to sell it. for me and my uly, again being a 2007...a breather re-route, NGK DCPR9EIX spark plugs, tps reset and replacing the stock map with a common racemap cured all the ills. it still does not heavy loads at 2000 rpm or so but then again no XB's do. if i were you i would try the plugs, the re-route and tps reset which is very easy on your 2008.

  5. #5
    Thanks lunaticfringe!

    I've now tried zip ties to keep the exhaust valve open. It hasn't cured the problem - but I love the deeper sound and new engine characteristics. It seems to pull more strongly from 2k rpm - and even roll on (just) from around 1.5k rpm if I'm being really lazy around town.

    The bile had a full service, so new plugs and air-filetr were put in - and certainly reduced but not cured symptoms.

    I've check ground wires. All tight - but think I'll take them apart, abrade and file back frame paint to ensure good contacts. I also noticed the left hand ground wire (by fuse box) touches the aluminium chassis for the battery. I don't know if that would have an effect - but I'll adjust it to not touch anyway.

    Then I'll continue to work through the list. I'm trying to find the clearest write up for the breather re-route... anyone got any suggestions?

  6. #6
    Having removed the battery I've noticed that the bracket I was concerned about is actually bolted into the earthing point - so I guess it makes no difference.

  7. #7
    Senior Member lunaticfringe's Avatar
    Join Date
    Feb 2011
    AmishLand, PA.
    Thanks lunaticfringe!
    my pleasure sir.
    regarding the breather re-route here's what i do....and there are variations but i do NOT run any type of filter or "catch can" at terminal end of your new breather hose. an inexpensive filter is fine but not required.
    1. remove air box cover, box lid, filter element, 4 torx screws for base plate, and with flat blade screw driver push the 2 breather tubes down thru their respective holes in airbox base plate. now as you gently push rubber air horn thru air box base pull up base and set aside. that will expose the air horn, top of motor, and your 2 breather from each head rocker box.
    get 3 ft length of 3/8th ID quality rubber hose normally used for oil line plumbing. you will also need one 3/8th T fitting. available at any auto parts store. trim the stock hoses from each cyl. head so that they will gently curve and attach to the T fitting and T fitting lies on top of motor just to left of airhorn assembly. then route your new 3/8th hose from end of T fitting down over top of rear of motor, out thru frame cavity at top of rear shock top mount and down to right side towards top of swingarm. terminate that hose there. plumb it neatly and use ample wire ties. when done double check that your breather fittings are securely pressed into their respective head grommets. they must be tight and secure. hope that helps.

  8. #8
    Senior Member lunaticfringe's Avatar
    Join Date
    Feb 2011
    AmishLand, PA.
    forgot to should find and use suitable rubber or plastic plug to seal the 2 remaining holes you will now have in the airbox base that formerly held the breather tubes. i glue them in from the bottom.

  9. #9
    Thanks lunaticfringe... may take me a little while to get organised for this one but sounds like a must!

    I've checked and cleaned/abraded all my ground wires - with no difference.

    Will try TPS as soon as the engine's cold again (as you say - easy to try so worth ruling out).

  10. #10
    Senior Member
    Join Date
    Jun 2013
    You NEED a filter on the there dude. Pressure is being built up and must release somehow. It's called a "breather" for a reason. When I had mine on the xb I could feel the filter and it was so it could still breathe and below it was a small length of tube that caught the liquids. Research pcv valves and engine crankcase blowby.

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