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Author Topic: Who used little washers to adjust needle positions?  (Read 797 times)

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Offline Deltarider

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Who used little washers to adjust needle positions?
« on: October 11, 2011, 10:24:00 AM »
Only once (in 32 years) I opened the tops of the (oldstyle) carbs of my CB500. This was to raise the needles by lowering the circlips one notch. I did this partly out of curiosity and also because Hondaman advises this in his Hondaman's thoughts to overcome the flat spot.
But... although his might be a good advice for some, maybe not for all.
Here's why. I can't rule out that for some reason in USA needles were positioned lower than in Europe. I remember having seen this - much to my surprise - in that little American Honda specifications booklet (that I mistrust by the way). Overhere for the 500 standard circlip position has always been the middle (3rd) position. So Hondamans advice might be less useful here, as needle were already higher to start with. Mine are now in 4th groove from top and although drivability is good, bike runs too rich at a bit above idle. For a experiment I'd like to have the needle positioned somewhere in between.
Now, here's the question. Did any of you ever experiment to raise the needle just a little bit by adding a small washer under that circlip instead of moving it?
« Last Edit: October 11, 2011, 10:27:41 AM by Deltarider »
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Offline TwoTired

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Re: Who used little washers to adjust needle positions?
« Reply #1 on: October 11, 2011, 11:00:15 AM »
No I haven't shimmed the needles.

But, I'm curious why you left out critical information, namely 649 set up carbs and the presence of the air filter inlet restrictor?  That restrictor is going to effect all the mixture delivery devices in the carbs.  And, as far as I know, no one outside of the Netherlands, and perhaps Germany, has any experience with those CB500 modifications.

You are quite right not to apply American Honda specs to that set up, imo.
But, I seem to recall you praising how well your bike ran with that inlet restrictor.  What is it exactly you are trying to "fix"?

I suppose I really shouldn't speak for Hondaman, but I think it unlikely that he has direct experience with 649 carbs and that inlet restrictor on a CB500.  And by the way, that inlet restrictor is precisely why the 649a slide needles are lower than the 627b set up.  I'd not be surprised if the needle taper angle, or diameter was different, too.
But, I fully admit at not having any direct experience with the 649a Carbs with an air filter inlet restrictor.  Most of my info on these has come from you.  But, I don't see why the physics would be different in the Netherlands/Germany.

Cheers,
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Offline Deltarider

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Re: Who used little washers to adjust needle positions?
« Reply #2 on: October 11, 2011, 12:00:03 PM »
Quote
No I haven't shimmed the needles.
Thanks, shim was the word I was looking for.
Quote
But, I'm curious why you left out critical information, namely 649 set up carbs and the presence of the air filter inlet restrictor?
  Because it's irrelevant. There was and is no need to cure anything. Only reason was because I read it in Hondaman's tips and my 500 just like all 500 and 550s has this infamous flat spot. Just an experiment.
Quote
But, I seem to recall you praising how well your bike ran with that inlet restrictor.

Yes, it does! It still pulls to 170 km/h even with 4 year old filter elements. See the dyno results I've posted before,
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What is it exactly you are trying to "fix"?
There's nothing to fix. Just curiosity and experimenting if I could improve somewhat on that flat spot with Hondaman's tip. See above. And yes, it improved somewhat but I don't like that rich running at idle and a bit above idle. It smells. That's why I would like to experiment with the needles in between. Long time ago I heard somebody suggesting a shim and I wondered if this is possible,

Quote
  And by the way, that inlet restrictor is precisely why the 649a slide needles are lower than the 627b set up.
Excuse me if I'm wrong, but the way I understood it needles were lower on USmodels (with larger mains). 
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I'd not be surprised if the needle taper angle, or diameter was different, too.
No, they have the same stamped number on the needles, 272304.
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But, I fully admit at not having any direct experience with the 649a Carbs with an air filter inlet restrictor.

Also the French models that had #100 mains and no airhorn have the needles in 3rd position.
Quote
Most of my info on these has come from you. But, I don't see why the physics would be different in the Netherlands/Germany.
But quality of gasoline certainly is. Even German and Dutch gaz are not the same.
« Last Edit: October 12, 2011, 08:27:23 AM by Deltarider »
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Offline dave500

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Re: Who used little washers to adjust needle positions?
« Reply #3 on: October 11, 2011, 01:40:39 PM »
if you have a 40 slow jet try a 38.
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Offline Kermit

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Re: Who used little washers to adjust needle positions?
« Reply #4 on: October 11, 2011, 02:10:03 PM »
its common practice on a klr650 to use a washer on the needle. You could always try and find a different taper.
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Offline TwoTired

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Re: Who used little washers to adjust needle positions?
« Reply #5 on: October 11, 2011, 02:39:44 PM »
Quote from: Deltarider on October 11, 2011, 12:00:03 PM

Quote
  And by the way, that inlet restrictor is precisely why the 649a slide needles are lower than the 627b set up.
Excuse me if I'm wrong, but the way I understood it needles were lower on USmodels (with larger mains). 

My understanding is that the 627B needle clip was in the 4th from the top (stock), same as the 022A.  This raises the needle and allows more fuel to flow when using a common pressure differential for comparison purposes.
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Offline robvangulik

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Re: Who used little washers to adjust needle positions?
« Reply #6 on: October 11, 2011, 04:20:00 PM »
Hi,
Not on my CB but on my CBR all needles are shimmed with a washer to position them between needle grooves, works very well and is easily to undo if you don't like the result.
On my bike this setup was checked and approved on a dyno bench.
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Offline Deltarider

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Re: Who used little washers to adjust needle positions?
« Reply #7 on: October 12, 2011, 08:13:02 AM »
Quote
My understanding is that the 627B needle clip was in the 4th from the top (stock), same as the 022A.  This raises the needle and allows more fuel to flow when using a common pressure differential for comparison purposes.

If this is true, then they were jetted on the rich side, certainly in combination with #100 main jets (cf French models that have the needle clip standard in the middle (= 3rd position)). Hondaman's advice to raise the needles even more than 4th would mean they would be in the 5th and maximum position. I'm not saying it's impossible but let me repeat: I mistrust this American Honda spec booklet.
« Last Edit: October 12, 2011, 10:30:06 AM by Deltarider »
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Offline Deltarider

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Re: Who used little washers to adjust needle positions?
« Reply #8 on: October 12, 2011, 01:04:38 PM »
« Last Edit: October 12, 2011, 01:55:01 PM by Deltarider »
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