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Autor Thema: Idle Air Adjustment R25/2  (Gelesen 213 mal)

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Kurt in S.A.

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Idle Air Adjustment R25/2
« am: 28 Juni 2020, 19:27:08 »

Carb is 1/22/44.  I'm thinking I might not have the idle air mixture set right.  My Bing manual says the setting is 1-1/2 turns out.  Does that seem right?  Usually that's a starting point, though.  How does one go about fine tuning that?  Do I get the engine warmed up and change the number of turns in (cuts out some air to make richer) and out (lets more air in to make leaner) and find the spot where the RPM goes the highest?  Maybe then a slightly bit richer from that point?

Thanks...Kurt
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Idle Air Adjustment R25/2
« am: 28 Juni 2020, 19:27:08 »

Hans Otté

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Re: Idle Air Adjustment R25/2
« Antwort #1 am: 28 Juni 2020, 20:42:01 »

Carb is 1/22/44.  I'm thinking I might not have the idle air mixture set right.  My Bing manual says the setting is 1-1/2 turns out.  Does that seem right?  Usually that's a starting point, though.  How does one go about fine tuning that?  Do I get the engine warmed up and change the number of turns in (cuts out some air to make richer) and out (lets more air in to make leaner) and find the spot where the RPM goes the highest?  Maybe then a slightly bit richer from that point?

Thanks...Kurt

Hi Kurt,
the values you are mentionning seems to be right, my docs are saying same.
But do any basic adjustments to the carb's settings only when the engine is in good working condition and really warmed up.
Oel temp should be stabilised around 70 to 80° to get an stable idle. A short ride will get the engine to that point.
HansO

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Kurt in S.A.

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Re: Idle Air Adjustment R25/2
« Antwort #2 am: 28 Juni 2020, 21:02:25 »

Thanks, HansO.  I'm more comfortable doing something like this on my R69S or my /7, although on the /7 I'm controlling a gas circuit, not air.  Also in those cases, I'm trying to balance the two cylinders...I still seem to only have the one on the R25/2!   ;D

Kurt
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Re: Idle Air Adjustment R25/2
« Antwort #3 am: 28 Juni 2020, 23:58:35 »

....and find the spot where the RPM goes the highest?  Maybe then a slightly bit richer from that point?
Exactly like that !

Cheers,
Sascha
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Kurt in S.A.

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Re: Idle Air Adjustment R25/2
« Antwort #4 am: 29 Juni 2020, 19:22:33 »

Just checked...the adjustment was at about 3/4 to 1 turn out.  So, I reset it to 1-1/2 turns out.  Will need to final adjust at the next ride.

Kurt
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Re: Idle Air Adjustment R25/2
« Antwort #5 am: 29 Juni 2020, 20:00:16 »

Just checked...the adjustment was at about 3/4 to 1 turn out.  So, I reset it to 1-1/2 turns out.  Will need to final adjust at the next ride.

Kurt

Hi Kurt,
when there a solution has been found, eventually a problem may be solved !
But don't forget : one resolved often means two new ones will propperly appear, soon.
Be happy, don't worry and good luck,
Hans
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Re: Idle Air Adjustment R25/2
« Antwort #6 am: 29 Juni 2020, 21:03:40 »

Well, you're probably right.  I'd posted about this before, but one issue that had been bugging me is some popping of the exhaust when I close throttle to shift gears.  I checked valve clearances last week and found them good, except that the intake was a bit tight...I like to run it at 0.15mm...exhaust was 0.20mm where I had left it.  The ride this past weekend showed the popping to be quite reduced, although I highly doubt that such a small change was the reason.

The other thing that I'm trying to resolve is that the engine surges a bit when running in lower gears at slow speeds in the neighborhood.  I was wondering if maybe my idle jet was too small...I don't know precisely if it is the 35 called out in the specs...it's been a while.  Then I thought about the mixture setting and how it might be affecting part throttle running.  I understand that the regimes of carb operation - idle jet, needle jet, main jet - all overlap at various throttle positions.  So, I'm trying to get the carb set where it should be and go from there.

Kurt
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Re: Idle Air Adjustment R25/2
« Antwort #7 am: 02 Juli 2020, 19:31:37 »

Hi Kurt,

find the setting as described. then make a test: try to find a "mountain road" an let the bike roll on high revs downwards. If the setting is too weak, there will be "bangs" to be heard in the muffler. Too, if the washer between exhaust and cylinderhead is worn out.
You will see, that there is a very small turn between "too weak" and perfect.

Good luck,

Jan
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Re: Idle Air Adjustment R25/2
« Antwort #8 am: 02 Juli 2020, 19:49:27 »

right, lean mixture can cause the popping. As leaks in the exhaust also can do.
One other potential cause are the ignition-advancer-springs.
If they lost tension over time, the fly-weights need lowers revs, until they swing back to their "late" position - the ignition is advanced although it isn't supposed to.
To check this, remove the generator lid, connect a strobe gun and aim on the advancer. Works best in a shaded or dark area.
Now rev it and watch the weights while closing throttle and rpm drops.
If they don't swing back till shortly before idle-rpm, it maybe worth a try to renew the springs.
But I suppose there will be an improvement already by setting idle more rich.
Next step could be to lift the needle one position - enrichens the next regime above idle. If required.

Cheers,
Sascha
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Re: Idle Air Adjustment R25/2
« Antwort #9 am: 02 Juli 2020, 20:09:23 »

Sascha -

In the position I found it, the idle mixture was screwed in too far, shutting off air making the idle circuit more rich.

The surging around the neighborhood at slow speed seemed to begin middle of last year when I lowered the needle from the 3rd to the 2nd position.  Ever since I got the bike, the mileage was around 50 mpg (US).  I felt it should have been better than that.  So I made the "crude" adjustment with the needle.  Now the gas mileage is more like 63 mpg.  I spend most of my time on 2/3-3/4 throttle so I'm likely on the main jet as well.  I was thinking that the needle adjustment might have affected the low range idle circuit.

I'll have to consider the advance springs...they might be original for all I know!!

Kurt
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