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xs650 > > Motorcycle Systems > > Engine > > Odd/sudden high idle...


Odd/sudden high idle...
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TeeCat
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PostPosted: October 3, 2009, 3:20 pm    Post subject: Odd/sudden high idle...

Hi, mates...

I took the TX out for about 20 miles this afternoon during a bit of spare time. Recently, I installed a new AGM battery and all there seems well.

The bike came off the choke quickly, up to temp, and ran beautifully, as has been the case recently. I topped the tank off, rode maybe five or so miles, and went home.

Just before I shut the bike off, she started to exhibit symptoms like you'd expect if your advance weights weren't returning, but my springs are new and they're snapping back nicely. There is no known history of vacuum leaks, and the floats have been fine since I set them properly and got new needle valves and seats last year.

Any thoughts? This is *snaps fingers* just like that... and the idle would hunt and climb... then come back down to 1500, where I have it set.

Caveat: the ONLY thing I did differently today was get gas. It sounds stupid, but I'm wondering if a topped off tank can cause this... maybe some oddball vacuum issue or something.

Also, if it were diaphrams or something, at-speed performance would be affected too, right? Again... this started right after I got gas and brought her home. Sunoco 93 octane.

Thanks -

TC
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TeeCat
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PostPosted: October 3, 2009, 3:21 pm    Post subject: Re: Odd/sudden high idle...

Oh, and is "edit" gone again?

TC
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yamaman
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Location: Perth Western Australia

PostPosted: October 3, 2009, 3:45 pm    Post subject: Re: Odd/sudden high idle...

Carbs sync'd?
aybe dump the fuel & try some new stuff if you think thats the drama!

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xsjohn
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Location: North Carolina USSA

PostPosted: October 3, 2009, 3:52 pm    Post subject: Re: Odd/sudden high idle...

Well I found these are timed a bit advanced....for all the high revs we seldom use...... any odity can effect the idol though .... fuel being right in there too......mine is the electronic model which is for me (for sure) to advanced from the factory....the ATU models should be looked at though..... if mine I would set it retarded a bit and see what happens.....did that to my 77 with good results.... I hate springs though and am thankful for the TCI.....even got 2 more extra boxes and pickup coils to make sure I never have spark problems...that was before all the jerks ran up the prices....... xsjohn
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nj1639
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PostPosted: October 3, 2009, 3:59 pm    Post subject: Re: Odd/sudden high idle...

I had a bizarro thing going on with my idle. Turn the wheel and the idle would go up. Problem was throttle cable routing.
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TeeCat
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PostPosted: October 3, 2009, 4:20 pm    Post subject: Re: Odd/sudden high idle...

Yup, my routing seems to be fine.

John... how much retarded is okay? Do you do it by eye, with a light?

I'll fire her up tomorrow and see if she does it again. She does seem to have a really sensitive idle circuit.

Oh, and carbs are synced... did it with the dead cyl method. This instance is very odd, but seems to coincide with some bizarre behavior one other time when I got gas and brought her right home afterward... peeing what looked like fuel or fuel vapor out the breather. Then it cleared up! So, call me crazy, but I wonder if some odd full tank vacuum issue doesn't "push" gas somehow while the pressure is equalizing. Any physicists here?

Will see what she does tomorrow.

TC
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yamaman
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PostPosted: October 3, 2009, 4:50 pm    Post subject: Re: Odd/sudden high idle...

Did you ever get around to adjusting your timing chain & valves?
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xsjohn
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PostPosted: October 3, 2009, 4:53 pm    Post subject: Re: Odd/sudden high idle...

If the atu is right I would set it maybe an 1/8" before the F mark........ see how it runs around corners at 2000....if it gets a bit cranky then I would play towards retard........timing is kind of run and see how it goes........ especially if you are like me and don't reve the s*** out of it.....and loose the nice lower revs for drivability.............wtf.....

xsjohn
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pamcopete
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PostPosted: October 3, 2009, 4:56 pm    Post subject: Re: Odd/sudden high idle...

TeeCat,

A full tank of gas creates more fuel pressure into the carbs, so if you had a marginally high float setting, the full tank pressure could cause the fuel in the bowl to go higher than it should.

It's something I'm surprised others haven't mentioned. To check your carb operation, especially fuel level in the bowl, with a full tank of gas.

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TeeCat
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PostPosted: October 3, 2009, 5:18 pm    Post subject: Re: Odd/sudden high idle...

pamcopete wrote:
TeeCat,

A full tank of gas creates more fuel pressure into the carbs, so if you had a marginally high float setting, the full tank pressure could cause the fuel in the bowl to go higher than it should.

It's something I'm surprised others haven't mentioned. To check your carb operation, especially fuel level in the bowl, with a full tank of gas.

Okay, now we're onto something, mates! Shocked

I was too curious, so I let her sit for about 90 minutes, played a bit of gutar, ate supper. Then I tried her again, just at idle and off-idle. she was cool, but not cold, so I used the choke and she wouldn't start. The instant I shut the choke off and kicked, she fired right up and settled into a lukewarm lope, but her throttle response is normal.

Now... remember the one other time this happened and I had a bit of fuelly oil dripping from the breather? Same thing just now! BOTH times... right after getting gas. So I'll bet this is the culprit here, Pete at all.

Pete... how would I check my tank vent to make sure it's venting optimally?

This can't be coincidence. I'll bet dollars to donuts it's the issue.

John... thanks for timing info.

yama... I did the timing chain this past summer. Every time i go to do the valves, life wants me to do something else. Sad Still have 5twins' how-to on the bench.

This is an interesting issue, Pete. Yes... surprised it has not come up before! Guess I'm good for something!

Pete... my neighbor's in love with those cool air plenums! Razz

TC
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xsjohn
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PostPosted: October 3, 2009, 5:41 pm    Post subject: Re: Odd/sudden high idle...

TC............ have you had that thing up on the expressway at 70 to see what happens...............

xsjohn
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TeeCat
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PostPosted: October 3, 2009, 5:46 pm    Post subject: Re: Odd/sudden high idle...

I've done quite a few runs up Rt. 40 at maybe 60-65, and some "vigorous" accelerations. She does very well, really, by my estimation. But I'm kind of a conservative rider.. fairly gentle with her yet. She seems really happy at speed, though. But I need to use her more for some stuff instead of the occasional 45-minute or hour local outing. I feel we're getting there...

TC
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TeeCat
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PostPosted: October 3, 2009, 5:58 pm    Post subject: Re: Odd/sudden high idle...

Oh, and John... had her to work and back once.. we were on some highway then, at about 65 0r so... she felt fine.

But I suppose the fix for this is to try to avoid bringing her right home after a top-off.

TC
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xsjohn
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PostPosted: October 3, 2009, 6:16 pm    Post subject: Re: Odd/sudden high idle...

Yea maybe the ole ""non"" viton float needles are a nusiance.... the later models fixed that...... maybe you could too per a last years discussion of that....everyone bitches about the BS34's ....not me.........they were just an upgrade with the EPA dicking them in the mean time...which can be removed.......more of that bullshit to come with Obama and all the green assholes....

xsjohn
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yamaman
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Location: Perth Western Australia

PostPosted: October 3, 2009, 6:28 pm    Post subject: Re: Odd/sudden high idle...

TeeCat wrote:
Every time i go to do the valves, life wants me to do something else. Sad Still have 5twins' how-to on the bench.TC

Good thing you printed it out Rolling Eyes
ight have to get you to re-type it into a thread for us, sometime when you've got a moment.

Even if you don't want to go to the length of adjusting them, it's easy to just pull the covers off & stick a feeler gauge in there.........Exact is not a major issue, but knowing that your somewhere in the ball park is!

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xsjohn
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PostPosted: October 3, 2009, 6:35 pm    Post subject: Re: Odd/sudden high idle...

Haven't adjusted my intakes in 40 thousand......checked them though with no change.... and no pitting on the stems either and not a sound from them.... Laughing .... oilers guys.. smack hand on forehead please....just a tiny bit of mechanical ability required......wtf.... Laughing

xsjohn
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