Let's face it boys, gas is getting "worser" by the day. This month the first page in Motorcycle Consumer News is titled "Ethanol". And either Cycle World or Rider magazine has an answer in the tech section stating the effects Ethanol and the EPA has had on our bikes performance. Even the newer bikes with injection are having some problems with uneven power bands, jerking, parts that handle gas leaking or other problems. The owners are mad, the dealers just throw up their hands, and the bikes get a bad name. As one author put it, "These companies don't want to sell less than perfect machines, but it is what it is." That quote isn't verbatim, but lean engines running weak gas don't work like they should. Try taking half the sugar and putting 1/3 more water in your tea, and you'll get my drift.  

Quote:
Bought a 2005 S40 about a month ago with ~4000 miles on it.  I'm now noticing that the bike jerks under acceleration.  Not sure how else to describe it other than uneven acceleration, even though I'm holding the throttle steady
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Your going to have to make up your mind,.......
is it jerking under acceleration, (sp plug, dirty carb, restricted gas supply, etc)

or is it jerking under steady throttle at low speed,......and 1 click on the choke improves it 90% ??? (white spacer mod will fix it)

You can forget the "bad gas" garbage !! Todays gas keeps carbs spotless, and all our engines have never run better !!  

Man I love the wealth of info at this forum.  Thanks for everyone's responses.

Dave, great call.  I'm in Austin, TX.  If there are any members in my area, it would be great to compare how my bike rides to someone else's.

Routy, I guess I was a little unclear.  I'm noticing this problem both during steady throttle and under acceleration but only at low speeds (under around 35 mph I'd say).  It seems to get a little better after I've ridden a good 20 minutes and at highway speeds.

Trippah, I set the idle by ear.  Is there an easy way to measure RPMs without special tools/instruments?

denistheruski wrote on 08/21/12 at 14:58:14:


I'm in San Antonio, and I am out riding every weekend.  I could probably meet you half way Saturday or Sunday.  Driftwood, Dripping Springs, Wimberley. that general area.   I have another ride that I am suppose to lead, but those plans haven't gelled yet.  Let me know if you want to do something, and which day, and I will see if I can nudge the other ride to the other day.

To accurately set the  idle you need a tachometer (inductive type) that reads the electrical impulses to your spark plug..either by wrapping a lead around the cable or a clip that clips onto the spark plug wire.  You are talking about 45 - 100 dollars depending on how fancy and if you want permantenly mounted and of course permanently working.  Some have added them I thin nk to their handlebar clusters..I''ll let the mechanics jump in because this has to be right before you start messing with the carb,

justin_o_guy2 wrote on 08/22/12 at 21:02:50:


It's #2 in this exploded view:
http://www.bikebandit.com/2005-suzuki-boulevard-s40-ls650/o/m147635#sch505570

The skinny round part at the bottom is metal, and is called "the slide".
Like JOG says, you will see it when you pull off the boot between the airbox and carb.  Can't miss it.