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Baffler186
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Joined: 31 May 2013
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PostPosted: 22:43 - 27 Jan 2017    Post subject: Carbs Reply with quote
Cb400a _ starts fine and idles fine, it accelerates normally if you open it up gradually, but if you whack it open it bogs and stays where it is.it also won't rev up to the redline. It does the same in neutral and in gear. Could it be the mixture needs adjusting? I considered having the carb cleaned and rebuilt but i did that with a previous bike and it made the problem worse.

It has new intake rubbers. I've put in new oil, oil filter and air filter, new plugs. I want to try adjusting the mixture before i pull it all apart but don't know how really. Is it just a case of fiddling with mixture screw whilst running, like you would the idle screw?
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redeem ouzzer
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Joined: 06 Oct 2015
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PostPosted: 23:10 - 27 Jan 2017    Post subject: Reply with quote
Mixture screw only affects idle > quarter throttle.

Sounds like mucky carbs.
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Commuter_Tim
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Joined: 08 May 2013
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PostPosted: 00:04 - 28 Jan 2017    Post subject: Re: Carbs Reply with quote
Baffler186 wrote:
Could it be the mixture needs adjusting? I considered having the carb cleaned and rebuilt but i did that with a previous bike and it made the problem worse.

Cleaning Carbs is only going to make a problem "worse" if the person fucked up the cleaning or that wasn't the problem in the first place.
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jaffa90
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Joined: 06 Apr 2016
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PostPosted: 00:06 - 28 Jan 2017    Post subject: Reply with quote
What year what carb is fitted?
It sounds short of fuel (lean) so is the air filter standard?
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Baffler186
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Joined: 31 May 2013
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PostPosted: 06:48 - 28 Jan 2017    Post subject: Reply with quote
jaffa90 wrote:
What year what carb is fitted?
It sounds short of fuel (lean) so is the air filter standard?
it's a 1980 model, carb is a vb24 i think. I doubt it has been cleaned before. Air filter is standard, I've just fitted a new oem one.
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Baffler186
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PostPosted: 06:50 - 28 Jan 2017    Post subject: Reply with quote
Ok thanks, i will get the carbs cleaned. There is a guy nearby who will ultrasonic clean and rebuild them for £50 plus cost of parts.
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Petemate
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Joined: 13 Nov 2015
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PostPosted: 08:50 - 28 Jan 2017    Post subject: Reply with quote
Baffler186 wrote:
Ok thanks, i will get the carbs cleaned. There is a guy nearby who will ultrasonic clean and rebuild them for £50 plus cost of parts.


Ultrasonic deffo the way to go with the VB carbs. I have one on my LA. It was a beggar to sort out but now OK. The slow running passages are a nightmare. Have a look on the Honda Twins forum - lots of info there and cutaway pics of the passages. Most interesting.
HTH
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Old Thread Alert!

The last post was made 9 years, 25 days ago. Instead of replying here, would creating a new thread be more useful?
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