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 '81 cb650c idle jets, how do i clean them? 
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Joined: Tue Aug 02, 2011 12:58 pm
Posts: 6
Post '81 cb650c idle jets, how do i clean them?
I'm working on a guys "new" 1981 CB650C and it has been sitting for a few years and the carbs were pretty gummy. The bike itself is in amazing condition and the previous owner took very good care of it. But it has the pressed in idle jets and all of them are clogged. I had them soaking for about a week with no luck. Any ideas on how i should get them cleaned out? and thanks for any help.

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Tue Aug 02, 2011 1:05 pm
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Joined: Mon Mar 06, 2006 1:53 am
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Location: southern Germany
Post Re: '81 cb650c idle jets, how do i clean them?
Welcome here! :D

Never tried myself but some here recommend guitar strings.
One may pull the jets out carefully with pliers, but I would avoid that if possible.
Have a look into the tank, too.

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Tue Aug 02, 2011 1:14 pm
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Post Re: '81 cb650c idle jets, how do i clean them?
the jets are actually down in the casting of the carb and there's no room to grab on them. If i knew how to get them back in and not falling back out i could just cut some threads in them and pull them out. The tank had alot of gas in it yet and some rust. I think i got all the loose rust out and i have a new petcock for it too.

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'83 Ford Ranger 302 4x4
'83 XR500R
'77 & '79 XL75
'85 ATC250SX
'85 Tecate
'87 TRX250X
'97 TRX300 4x4
'04 TRX450R
2 '80/'81 JD spitfires


Tue Aug 02, 2011 1:23 pm
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Joined: Wed Oct 07, 2009 5:13 am
Posts: 145
Post Re: '81 cb650c idle jets, how do i clean them?
i wouldn't take them out.

there is debate about the guitar string method, and some claim it can harm the pressed in jets by inadvertently making them larger.

having said this, i have cleaned them with a .010" string. you can buy a single string at the guitar store, so to be safe, get a .008 or .009.

there are some good tutorials on youtube for carb cleaning. if i were you, i would completely dissassemble the carbs (don't mix parts from carb to carb) so that you can keep the gaskets and o-rings safe, and then hit the jets with lots of carb cleaner using the guitar string to gently make sure passages are clear. an air compressor is ideal for blowing out passages, but a can of it works alright (though it reacts with carb leaner and makes a little foam sometimes).

putting the carbs back together is a bit tricky, especially in regards to the choke lever setup.

good luck!


Tue Aug 02, 2011 2:11 pm
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Joined: Thu Jan 04, 2007 2:26 am
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Post Re: '81 cb650c idle jets, how do i clean them?
One question I've been asking myself lately is, do the idle jets have emulsifier tubes like the mains do? If so they'd have to be removed to be completely cleaned...

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Tue Aug 02, 2011 3:34 pm
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Location: Denver CO USA
Post Re: '81 cb650c idle jets, how do i clean them?
The idle jets on the 81 are virtually impossible to remove. They are recessed in to the casting unlike the 79/80. But in 82 they are screw in. Virtually the same carb as the 81. I have a couple sets of each and been meaning to look into it but been lazy.

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Tue Aug 02, 2011 7:42 pm
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Joined: Wed Oct 07, 2009 5:13 am
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Post Re: '81 cb650c idle jets, how do i clean them?
that's a good question...i was always under the impression that they didn't.

i've taken only one other set of carbs apart, a virago's that had removal pilot jets, which did not have emulfisier tubes. the mains did, however.

i think that the pilot jets are small enough that they shoot a fine mist, whereas the larger mains need to froth up their volume of fuel.


Tue Aug 02, 2011 7:48 pm
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Joined: Wed Oct 07, 2009 5:13 am
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Post Re: '81 cb650c idle jets, how do i clean them?
if you look at the picture of the jets in the kit, they don't have tubes.

thanks google!!!


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Tue Aug 02, 2011 7:50 pm
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Joined: Tue Aug 02, 2011 12:58 pm
Posts: 6
Post Re: '81 cb650c idle jets, how do i clean them?
I've had the jets soaking for awhile now. I already tried an air compressor to get them clean. I had no air leaks at all and had 100psi trying to go through them. Next i'm going to try to soak them with ethanol. I here it's suppose to eat up the varnish that "real" gas develops. and i may look over ebay for a set of '82 carbs just to see what kind of price they'll be.

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'83 Ford Ranger 302 4x4
'83 XR500R
'77 & '79 XL75
'85 ATC250SX
'85 Tecate
'87 TRX250X
'97 TRX300 4x4
'04 TRX450R
2 '80/'81 JD spitfires


Wed Aug 03, 2011 12:05 pm
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Joined: Fri Mar 03, 2006 7:20 am
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Location: Denver CO USA
Post Re: '81 cb650c idle jets, how do i clean them?
Ok took apart one of the 82 carbs and it does have screw in slow jets.
In the previous pic it is the upper left most jet. And yes it is imultion tube like with the holes on the side.
A FYI also the mains do screw into tubes.

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Wed Aug 03, 2011 2:12 pm
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Post Re: '81 cb650c idle jets, how do i clean them?
davesee wrote:
if you look at the picture of the jets in the kit, they don't have tubes.

thanks google!!!


What year is that kit for?? Looks like a '79 according to the info Terry just gave about the jet not being recessed into the carb casting.

FYI, that picture does show idle jet emulsion tubes...


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Wed Aug 03, 2011 2:50 pm
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Joined: Fri Mar 03, 2006 7:20 am
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Location: Denver CO USA
Post Re: '81 cb650c idle jets, how do i clean them?
The jet is recessed but it screws out. The 81 is pressed. As u know the 79/80 is pressed but u can persuade it out as its external of the casting. Looks like a 81/2 kit with the aluminum plug for the slider.

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Wed Aug 03, 2011 3:01 pm
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Joined: Tue Aug 02, 2011 12:58 pm
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Post Re: '81 cb650c idle jets, how do i clean them?
the guy that owns the bike already had the kits for them and they look identical to the pic listed and it says '81-'82 on them.

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'83 Ford Ranger 302 4x4
'83 XR500R
'77 & '79 XL75
'85 ATC250SX
'85 Tecate
'87 TRX250X
'97 TRX300 4x4
'04 TRX450R
2 '80/'81 JD spitfires


Thu Aug 04, 2011 11:50 am
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Joined: Wed Oct 07, 2009 5:13 am
Posts: 145
Post Re: '81 cb650c idle jets, how do i clean them?
mine is an 80 and they are pressed in, so that kit pictured must be the 81/2.

pinhead: isn't that big one with the emulsion tubes the main jet? maybe i understand it wrong?


Thu Aug 04, 2011 11:55 am
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Joined: Thu Jan 04, 2007 2:26 am
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Post Re: '81 cb650c idle jets, how do i clean them?
davesee wrote:
mine is an 80 and they are pressed in, so that kit pictured must be the 81/2.

pinhead: isn't that big one with the emulsion tubes the main jet? maybe i understand it wrong?


The main jet emulsifier would be larger. The picture isn't showing the main emulsifier.

The picture is showing two main jets (middle of the picture). Different sizes, perhaps?

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Thu Aug 04, 2011 3:30 pm
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