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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Engine slowdown/death after letting go of throttle /cgi-bin/YaBB.pl?num=1368316603 Message started by MeLikeBike on 05/11/13 at 16:56:43 |
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Title: Engine slowdown/death after letting go of throttle Post by MeLikeBike 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'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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Title: Re: Engine slowdown/death after letting go of thro Post by Serowbot on 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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Title: Re: Engine slowdown/death after letting go of thro Post by apache snow on 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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Title: Re: Engine slowdown/death after letting go of thro Post by Serowbot on 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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Title: Re: Engine slowdown/death after letting go of thro Post by MeLikeBike on 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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Title: Re: Engine slowdown/death after letting go of thro Post by 87 savage on 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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Title: Re: Engine slowdown/death after letting go of thro Post by Super Thumper on 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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Title: Re: Engine slowdown/death after letting go of thro Post by justin_o_guy2 on 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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Title: Re: Engine slowdown/death after letting go of thro Post by MeLikeBike on 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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Title: Re: Engine slowdown/death after letting go of thro Post by justin_o_guy2 on 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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Title: Re: Engine slowdown/death after letting go of thro Post by 87 savage on 05/15/13 at 01:37:37 4854595A51583C0 wrote:
Just curious, why did you replace the rocker arms? Is it possible they are adjusted too tight. :-? |
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Title: Re: Engine slowdown/death after letting go of thro Post by MeLikeBike on 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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Title: Re: Engine slowdown/death after letting go of thro Post by 87 savage on 05/15/13 at 09:02:23 Other than the dip at idle it runs fine? |
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Title: Re: Engine slowdown/death after letting go of thro Post by apache snow on 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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Title: Re: Engine slowdown/death after letting go of thro Post by MeLikeBike on 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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Title: Re: Engine slowdown/death after letting go of thro Post by 87 savage on 05/15/13 at 16:06:28 So how many tanks of gas since this started? |
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Title: Re: Engine slowdown/death after letting go of thro Post by MeLikeBike on 05/19/13 at 19:16:44 Only really been one tank. I don't ride nearly enough :( So, i bumped up the idle to what I would think is well above 1000, or maybe 1200. It seems to fix the problem of the slowdown. There's a tiny bit of perceived dip when I rev the engine, but the idle seems to enforce a higher rpm. I *did* notice a few posts in the forum regarding issues with the mix screw not really doing much...mine is the same way. If I find the minimum numbers of turns out before it slows down (say 1 or 1.5), once I get above that, the engine runs the same all the way up to 4 turns out. The carb tuning guides here imply that I should notice a narrower band of higher rpms (between 2 and 3 or so, right?) I don't see that...it's either full speed or chug-to-death when I turn it way in. Maybe that's another symptom of my (non)problem? Again, this idle dipping is a new phenomenon (or newly noticed). Maybe a stuck slide or clogged needle? |
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Title: Re: Engine slowdown/death after letting go of thro Post by 87 savage on 05/20/13 at 02:08:12 2A363B38333A5E0 wrote:
So I just reread this post and I noticed that you said you didn't have, or notice this issue before you washed the bike and adjusted the idle mixture screw. I don't see how washing the bike has anything to do with it, it's been long enough for everything to be nice and dry. But, why did you feel you needed to tune the carb after changing the rocker arms? Did it run differently at that time? :-? |
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Title: Re: Engine slowdown/death after letting go of thro Post by MeLikeBike on 05/20/13 at 05:16:13 Well, since the idle mixture plug had been taken out by the previous owner, I assumed that he may have monkeyed with it. And since I replaced the rocker arms, I figured that that would affect the motor operation enough to justify an optimization. From what I read, the idle mix tuning seemed pretty straightforward, so I wasn't worried about messing things up too bad. But as I said, the tuning suggesting of finding the narrow band of highest RPMs wasn't possible. Playing some of my old videos (from my rocker arm anguishing) has my idle much higher than I thought it was, so Serowbot and the others probably were right, and I was probably just dumb on this idle dipping thing. I wish the bikes had a tach, so there wouldn't be the phantom memories kicking in of what my idle *was* vs what it really was. I have a Dyna muffler and some HD clamps on order from Ebay, so I'll likely be diving into the mix tuning again, and from what I read, the white spacer mod. So I'll likely have a look in the carb at some point...if there's a dead stinkbug or something in there, I'll let you all know ;) |
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Title: Re: Engine slowdown/death after letting go of thro Post by LANCER on 05/20/13 at 06:11:08 If the carb is functioning normally then you should NOT be able to turn the pilot screw from 1-4 turns out without any change in the engine running. Since you are now running fairly well then it might clear itself out with just more road time; see if it does. If not then you can always pull it and do a thorough cleaning later. |
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Title: Re: Engine slowdown/death after letting go of thro Post by 87 savage on 05/20/13 at 15:41:38 Ditto what Lancer said. Besides you know you,re dying to tear that carb apart! ::) |
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