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scotto75 |
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scotto75 Renault 5 Driver
Joined: 13 Mar 2016 Karma :
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Posted: 00:00 - 05 Nov 2018 Post subject: |
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I used the brass nipple to replace the external overflow tube on the bottom of the bowl, not the internal part.
Yes, you’re right about the metal strip that connects the choke on both carbs.
I hooked the carbs up tonight and measured float level by screwing in some clear tube into the drain hole, and pouring petrol into a funnel that ran to some fuel hose. I have set the float heights at 26mm, as recommended on the Honda Twins forum, but the level came out at 6mm below the gasket line. My understanding is that I should be aiming for 3-4mm under the gasket, so I could adjust the float height to get the level in the tubes higher by 2-3mm?
TBH thought my carbs were running a bit rich. The jets are all the right size, but wasn’t convinced about these Keyster rebuild kits, or the press in jets with o’rings and a spring that holds them down when the bowl is screwed back on. The engine idles nice but bogs down the second you open up the throttle a fraction.
BTW, it’s not gold. it was Maroon but someone painted it black at some point. I have a gold tank on a CB350. ____________________ Honda ‘73 CB350, ‘80 CG125, ‘88 CG125, '73 Triumph T140V |
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bikenut |
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bikenut World Chat Champion
Joined: 21 Nov 2011 Karma :
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scotto75 |
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scotto75 Renault 5 Driver
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scotto75 |
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scotto75 Renault 5 Driver
Joined: 13 Mar 2016 Karma :
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Posted: 07:56 - 06 Nov 2018 Post subject: |
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I’m not convinced by the quality of the Keyster rebuild kits. When I got the bike I instantly stripped the carbs, ran them a couple of times through an ultrasonic cleaner and rebuilt them with the jets and tubes from the kits.
There are three orifices, a pilot jet #35 with a rubber bung, the needle tube and a secondary jet #70, and the main jet #100 and tube.
As an example of a difference which I find a little suspect, the original needle tube needed to be tapped gently out of its orifice. The replacements Keyster part doesn’t stay in the orifice. It is held in by the jet, which has an o-ring and is held in by a spring clamp, which is held down when the float bowl is screwed down. When the clamp and jet are removed, the tube falls out. This is the same for the main jet tube too.
As a comparison I will go back to the original parts removed from the carbs when I rebuilt them. They were put through the ultrasonic cleaner so should be clear, but ____________________ Honda ‘73 CB350, ‘80 CG125, ‘88 CG125, '73 Triumph T140V |
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bikenut |
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bikenut World Chat Champion
Joined: 21 Nov 2011 Karma :
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bikenut |
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bikenut World Chat Champion
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scotto75 |
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scotto75 Renault 5 Driver
Joined: 13 Mar 2016 Karma :
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Posted: 08:46 - 10 Nov 2018 Post subject: |
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Thanks for persevering with me bikenut. I appreciate your help greatly. The carb is here on CMS
https://www.cmsnl.com/honda-cb250k3_model50719/partslist/0050.html#.W-aHSaSnzYU
I have replaced the jets and tubes with the original ones that came out of the carbs when I put them through the ultrasonic cleaner. The tubes fit a lot better than the Keyster ones. The o-rings on the primary and secondary jets were crap so swapped with the rebuild ones. After some adjustments of the mixture with the Colortune and sync with the Synchrometer (which is my new favourite tool BTW!) I still end up with a strong idle that stalls when the throttle is opened just slightly.
I have read the Haynes and Honda carb manuals and my understanding is that the primary main jet supplies fuel between the idle circuit and the needle jet as the throttle butterfly opens. It’s supposed to smooth the transition between the two.
The idle jet gets fuel from a hole in the main jet and the mixture screw controls how much aerated fuel is allowed through. Screwing in reduces the amount making it leaner, etc.
The first cause is blocked jets restricting air or fuel flow. I have probably assumed that all passages were cleaned when put through the ultrasonic cleaner, but I will have to go through and double check.
Next is air leaks. I’m not having any issues elsewhere with rev hunting or hanging high revs. But maybe it could be coming through the throttle bushes when the throttle opens? The Colortune shows bright orange when the needle jet should be in control making me think it is rich and not lean.
I’ve tried both Keyster and original needles with the same result, but could it be when the needle lifts it gets too much fuel?
Time to get the carbs off again! ____________________ Honda ‘73 CB350, ‘80 CG125, ‘88 CG125, '73 Triumph T140V |
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Hong Kong Phooey |
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Hong Kong Phooey World Chat Champion
Joined: 30 Apr 2016 Karma :
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Posted: 09:14 - 10 Nov 2018 Post subject: |
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scotto75 wrote: | Thanks for persevering with me bikenut. I appreciate your help greatly. The carb is here on CMS
https://www.cmsnl.com/honda-cb250k3_model50719/partslist/0050.html#.W-aHSaSnzYU
I have replaced the jets and tubes with the original ones that came out of the carbs when I put them through the ultrasonic cleaner. The tubes fit a lot better than the Keyster ones. The o-rings on the primary and secondary jets were crap so swapped with the rebuild ones. After some adjustments of the mixture with the Colortune and sync with the Synchrometer (which is my new favourite tool BTW!) I still end up with a strong idle that stalls when the throttle is opened just slightly.
I have read the Haynes and Honda carb manuals and my understanding is that the primary main jet supplies fuel between the idle circuit and the needle jet as the throttle butterfly opens. It’s supposed to smooth the transition between the two.
The idle jet gets fuel from a hole in the main jet and the mixture screw controls how much aerated fuel is allowed through. Screwing in reduces the amount making it leaner, etc.
The first cause is blocked jets restricting air or fuel flow. I have probably assumed that all passages were cleaned when put through the ultrasonic cleaner, but I will have to go through and double check.
Next is air leaks. I’m not having any issues elsewhere with rev hunting or hanging high revs. But maybe it could be coming through the throttle bushes when the throttle opens? The Colortune shows bright orange when the needle jet should be in control making me think it is rich and not lean.
I’ve tried both Keyster and original needles with the same result, but could it be when the needle lifts it gets too much fuel?
Time to get the carbs off again! |
Blowing through smaller airways with carb cleaner with the WD40 straw attached worked for me, you can see it's unblocked as the jet blasts through. Poking through with guitar string is an option if it's really gummed. ____________________
'81 CG125, '97 FZS600 : '99 CBR600F4, '09 KTM RC8 |
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scotto75 |
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scotto75 Renault 5 Driver
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bikenut |
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bikenut World Chat Champion
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bikenut |
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bikenut World Chat Champion
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bikenut |
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bikenut World Chat Champion
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talkToTheHat |
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talkToTheHat World Chat Champion
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Posted: 15:47 - 10 Nov 2018 Post subject: |
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I've got a twin pressure gauge carb sync thing somewhere, don't use it anymore as I no longer have a twin with a balance screw that vibrates loose. like half of this https://youtu.be/t0qf11BOx6o If it helps It's available for postage cost and a beer ____________________ Bandit. does. everything. |
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scotto75 |
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scotto75 Renault 5 Driver
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scotto75 |
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scotto75 Renault 5 Driver
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bikenut |
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bikenut World Chat Champion
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scotto75 |
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scotto75 Renault 5 Driver
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bikenut World Chat Champion
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scotto75 |
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scotto75 Renault 5 Driver
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Old Thread Alert!
The last post was made 5 years, 159 days ago. Instead of replying here, would creating a new thread be more useful? |
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