SuzukiSavage.com - Engine slowdown/death after letting go of throttle

MeLikeBike

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Monroeville, PA
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Engine slowdown/death after letting go of throttle
05/11/13 at 16:56:43

Hi everyone,

New problem...when I'm sitting in neutral, and rev the engine, when I let go of the throttle, the engine slows to a near death, sometimes to a compete stall. I've uploaded a video:

https://www.youtube.com/watch?v=DagCJxxGyr8

My most recent change is a new battery (my old one was still ok, but was getting old, and I'd suspected a weak spark). I have been playing around with the idle mix screw, because over winter I'd put new cam followers in, so I thought I'd try to tune the carb. (the previous owner had already removed the removed idle screw cover.)

I'm about 2.5 turns out, though the engine runs okay anywhere from 1.5 to more than 3 turns out. I've never opened the carb, so AFAIK I have the original jets (though the missing idle screw cover maybe points toward a prior rejet?)

I haven't noticed this since putting the new battery in, though something similar may have happened while I was riding (which let me to believe a weak spark, etc.etc.). So the battery may be a red herring.

Thoughts? Maybe slow fuel line? (I have a Raptop.) Water somewhere? (I washed the bike recently.)

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2003 Savage LS650, Dyna, 2/3 Spacer

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Serowbot YaBB Moderator ModSquad Offline OK.... so what's the speed of dark? Posts: 28627 Tucson Az Gender:	Re: Engine slowdown/death after letting go of thro Reply #1 - 05/11/13 at 17:46:03 Yer' idle speed's kinda' low... (bike sounds like it's chuggin' instead of purrin')...Try raising it a couple hundred RPM... That's not good for the cam,.. and it often does cause that idle dip... ... (knurled screw/knob,.. near the choke is idle speed)...
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apache snow-FSO

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Re: Engine slowdown/death after letting go of thro
Reply #2 - 05/11/13 at 18:21:17

Thats a symptom of a too rich fuel mixture, but since you haven't changed any thing on the carb that couldn't be it. Maybe the carb needs cleaning. The slide could be sticking and causing it.

Turning up the idle could help and its an easy one to try. Two and a half turns out on the fuel screw is about right if you are not at a real high elevation.

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2012 Honda Shadow Spirit

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Serowbot YaBB Moderator ModSquad Offline OK.... so what's the speed of dark? Posts: 28627 Tucson Az Gender:	Re: Engine slowdown/death after letting go of thro Reply #3 - 05/11/13 at 18:25:58 +1... you do get a little rich bump when you let off the gas... the engine dying from it can indicate too rich... ... but,.. your idle is low... this is probably the cause of your needing new cam followers... (low oil pressure at too low of an idle)... So,.. I'd try raising it a bit...
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MeLikeBike Junior Member Offline Newbie, but Goodie Posts: 59 Monroeville, PA Gender:	Re: Engine slowdown/death after letting go of thro Reply #4 - 05/11/13 at 18:56:20 So I've raised my idle speed a bit...helps a little, but still get the dip. Incidentally, is there a youtube clip out there with a good example of idle speed?
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87 savage

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Re: Engine slowdown/death after letting go of thro
Reply #5 - 05/11/13 at 20:03:13

Hey, found this on a CV Carb tuning instructions site:

"NOTE: A rich problem gets worse as the engine heats up.
If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture."

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His: 1987 LS650F stock except for 98 engine, Dyna muffler. Hers: 2008 S40 with factory bags, windshield and sissybar.

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Super Thumper Senior Member Offline 2001 LS650 With 97mm Big Bore Kit, Stage III Cam. Posts: 469 Windsor, Vermont Gender:	Re: Engine slowdown/death after letting go of thro Reply #6 - 05/11/13 at 20:56:45 Mine did that when I first got it also....adjusting the idle a little higher helped some but when I drilled out the pilot jet screw plug and adjusted the pilot screw is when the problem went away for me.
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justin_o_guy2

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Re: Engine slowdown/death after letting go of thro
Reply #7 - 05/12/13 at 09:54:50

Yea, adjust the little screw behind the brass plug, make sure the idle is in its Happy PLace.

MIne is a persnickety outfit. First started, it needs bumped up to idle right & make sure were oilin good. After 5 minutes or so of riding, its time to back off the idle just a hair. & It takes about 30 minutes of riding to get it all warmed up & the idle set right. Thankfully, the idle adjusts with fingertips,, its almost as if the engineers knew something,,

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MeLikeBike

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Re: Engine slowdown/death after letting go of thro
Reply #8 - 05/14/13 at 17:31:42

so I bumped up the idle and went for a ride. (Hard to type...fingers numb from 50 degree evening trip). After about 15 min, I pulled over, and tried the throttle drop, and I still get the dip in the idle. I took out a screw driver and tried it again and again after consecutive clockwise 1/4 turns of the idle mix screw. No real difference, until the motor started to chug and slow down from turning in the screw too far.

Do you guys think I'm gonna have to go into the carb? Or even pull it off the bike?

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2003 Savage LS650, Dyna, 2/3 Spacer

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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Engine slowdown/death after letting go of thro Reply #9 - 05/14/13 at 21:18:56 How much did ya bump the idle? You sure youve got it up to 1,000 or better?
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87 savage

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Re: Engine slowdown/death after letting go of thro
Reply #10 - 05/15/13 at 01:37:37

MeLikeBike wrote on 05/11/13 at 16:56:43:

Hi everyone,

New problem...when I'm sitting in neutral, and rev the engine, when I let go of the throttle, the engine slows to a near death, sometimes to a compete stall.
I have been playing around with the idle mix screw, because over winter I'd put new cam followers in, so I thought I'd try to tune the carb. (the previous owner had already removed the removed idle screw cover.)

I'm about 2.5 turns out, though the engine runs okay anywhere from 1.5 to more than 3 turns out. I've never opened the carb, so AFAIK I have the original jets (though the missing idle screw cover maybe points toward a prior rejet?)

I haven't noticed this since putting the new battery in, though something similar may have happened while I was riding (which let me to believe a weak spark, etc.etc.). So the battery may be a red herring.

Thoughts? Maybe slow fuel line? (I have a Raptop.) Water somewhere? (I washed the bike recently.)

Just curious, why did you replace the rocker arms? Is it possible they are adjusted too tight. Huh

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His: 1987 LS650F stock except for 98 engine, Dyna muffler. Hers: 2008 S40 with factory bags, windshield and sissybar.

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MeLikeBike

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Posts: 59
Monroeville, PA
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Re: Engine slowdown/death after letting go of thro
Reply #11 - 05/15/13 at 03:50:03

I replaced the rocker arms because the pads were worn, and I was getting a TACK TACK TACK TACK TACK sound.

But this new problem is newer than replacing those....I noticed this idle dipping after a series of:
- washing the bike
- loosening the belt little
- adjusting the mix screw for the first time
- changing the battery

I dont' have a strict comparison before or after any of these changes because I have ridden the bike infrequently (maybe once a week) since the Spring has been up and down in temps and my life is up and down with free time.

Maybe there's some loose hose from taking off the seat/battery?
Maybe the new battery is crap?
Maybe a loose wire?
Maybe water in somewhere from the wash?

I'll have to take a video of the new idle speed for those that wanna hear it...it's higher than I think it needs to be...but the idle shouldn't dip at all, right? Turning the idle up just gives the engine a little more oompth to pull itself out of this dip, right?

Everyone is saying that this sort of dip is from running too rich, but I turn that screw in until the motor almost cuts out, and it doesn't changes things.

I read last night someone complaining of this sort of thing after adding Seafoam. I don't remember exactly when I added Seafoam, but it was relatively recently.

Sorry to ramble, but I don't know enough about engines/carbs to know what makes a difference and what doesn't (and what, say, washing your bike can lead to if you make a boo boo).

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2003 Savage LS650, Dyna, 2/3 Spacer

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87 savage Full Member Offline Gone riding! Posts: 249 Maine Gender:	Re: Engine slowdown/death after letting go of thro Reply #12 - 05/15/13 at 09:02:23 Other than the dip at idle it runs fine?
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apache snow-FSO Serious Thumper Offline Posts: 509 Gender:	Re: Engine slowdown/death after letting go of thro Reply #13 - 05/15/13 at 09:38:10 Have you checked the air-filter. A dirty one will cause a rich condition. And did the previous owner change jets
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MeLikeBike Junior Member Offline Newbie, but Goodie Posts: 59 Monroeville, PA Gender:	Re: Engine slowdown/death after letting go of thro Reply #14 - 05/15/13 at 09:42:08 The bike is running okay...there is a bit of a chug sometimes at about 1/4 throttle. No engine dying while I'm moving. No problems starting. I'll check the air filter soon, though this happened fairly suddenly to suspect that.
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