Author Topic: CB500 needle jet holder removal  (Read 260 times)

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Online Cevan

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CB500 needle jet holder removal
« on: December 05, 2024, 05:37:03 PM »
Digging into the carbs on my ‘72 CB500 K1.  Rebuild kit from David Silver Spares contains a needle jet holder.  No clue how to remove this.  It doesn’t appear to screw in.  The main jet sits on top.  After removing that, the needle jet holder is recessed into the carb body.  Not sure if I’m better off just leaving it in and just replacing the needle.  Thoughts?

Hoping the ultrasonic cleaner improves things.  These carbs are crusty.


Online scottly

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Re: CB500 needle jet holder removal
« Reply #1 on: December 05, 2024, 06:54:50 PM »
Use a small wood dowel to push the needle jet/emulsion tube out, and make sure the holes in the sides are clear.
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Offline denward17

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Re: CB500 needle jet holder removal
« Reply #2 on: December 05, 2024, 07:50:29 PM »
From the top...

Offline bryanj

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Re: CB500 needle jet holder removal
« Reply #3 on: December 05, 2024, 08:44:53 PM »
The general consensus is to reuse cleaned original brass unless damaged as the kits are not acurate, especially needle tapers
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Offline dave500

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Re: CB500 needle jet holder removal
« Reply #4 on: December 06, 2024, 02:49:26 AM »
soak all your genuine brass in vinegar overnight,it wont dissolve it at all,itll clean up nice after that with some fine steel wool and mild kitchen abrasive cleaner,i like to lightly chamfer the emulsion tube holes.

Offline Oddjob

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Re: CB500 needle jet holder removal
« Reply #5 on: December 06, 2024, 04:20:12 AM »
Speaking from experience I can say that getting those float bowls to clean up will be hard. That crust/mold that's on them hides a massive amount of corrosion underneath as a rule, I've just done a 550 clutch case that had the same stuff on it, I call it Knacker Rash  :D :D, underneath was a LOT of pinprick holes in the alloy. They didn't go very deep but the surface looked like the moons surface.

You'd also be advised to separate the lifter rod from the carb bracket, by drilling out the retaining rivet on the left side of the bracket. The rod usually rusts like hell if left in a damp environment, so much so I was having to get them hard chromed before I had some made in stainless steel, still got a couple if you find you want one. I've had the carb bracket both powder coated and ceramic coated in various colours, silver, chrome and black actually. All looked ok afterwards, ceramic coating is far better as it's much much thinner. The butterfly system can be zinc coated again and it will look like new afterwards.

I could post pics of some I've done to give you some ideas but the website I use to post pics is down atm.


Offline MauiK3

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Re: CB500 needle jet holder removal
« Reply #6 on: December 06, 2024, 06:46:46 AM »
The ultrasonic will really help. Check what cleaner you use, some are harmful to the aluminum.
Straight Simple Green is one not to use, diluted about 50-50 works well.
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Offline BenelliSEI

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Re: CB500 needle jet holder removal
« Reply #7 on: December 06, 2024, 04:12:41 PM »
I use simple green concentrate in my ultrasonic tank, mixed 4:1 with distilled water (4 parts). I leave carbs in for less than 30-35 minutes with no real effect. The small brass I soak in carb cleaner for a bit, then put them in a small container in the tank too.

For my Sandcast Project I took the carb bodies, tops, and float bowls to be vapour blasted. WOW. Look like new!
« Last Edit: December 06, 2024, 04:14:13 PM by BenelliSEI »

Online Cevan

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Re: CB500 needle jet holder removal
« Reply #8 on: December 08, 2024, 06:24:56 AM »
Thanks for the replies.  Got the tubes out.  So far I’ve used my ultrasonic cleaner with distilled water, vinegar and dish soap.  Then hit them with the soda blaster.   

The rod spins freely in the carb bracket.  Probably will just leave it be.  The float bowl drain screws came out a little bugged.  Will probably have to chase the threads and replace the screws.


Offline Oddjob

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Re: CB500 needle jet holder removal
« Reply #9 on: December 08, 2024, 10:15:02 AM »
Don't forget to poke something down the float bowl drain screws as the crud builds up inside them and prevents them from draining as they should do.

How'd the float bowls come out in the ultrasonic? Did it affect the rash?