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 Post subject: twin carbs
PostPosted: Sat Apr 04, 2009 6:52 pm 
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848cc
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Location: Adelaide
could anyone give me some insight on twin carbs as have old set been put, on reving at start to high 5000rpm no acelarator or choke on, set at two turns after flat in pot as per manual.

any help great.


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PostPosted: Sat Apr 04, 2009 7:10 pm 
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could be a lot of things, but basically you're getting too much air in there

butterflies stuck open - check that they are shutting fully, and that they're hitting the idle screw

you might want to check that the linkage isn't too wide to go between the carbs - I had a set once that needed the linkage shortened a couple of mm as when the throttle was shut, it was pushing the butterflies outwards. The effect was that the butterflies weren't shutting properly, and were badly damaged

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 Post subject:
PostPosted: Sat Apr 04, 2009 7:16 pm 
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Basically i would check the linkages so as to set up the air flow first, make sure the butterflies are closig evenly, then screw the idle screws out ( could have one screw screwed right in , maybe?) , then check mixture screws and set as per book so as to get a starting point. There are some posts on here not too long ago that will give you a step by step guide to setting up twin carbs, do a search and see how you go.

Colin


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 Post subject: twin carbs
PostPosted: Sat Apr 04, 2009 8:10 pm 
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have sleeved butterflies and checked closing all ok ??


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PostPosted: Sat Apr 04, 2009 8:58 pm 
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It doesn't take much throttle opening to free rev the engine - also check for air leaks

Daniel

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 Post subject:
PostPosted: Sat Apr 04, 2009 9:28 pm 
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If the bushes on the throttle shaft have been fitted wrong it will leak air past the edge of the butterfly.


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 Post subject: Re: twin carbs
PostPosted: Sat Apr 04, 2009 9:41 pm 
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Location: Under the bonnet son!
west end clubby wrote:
have sleeved butterflies and checked closing all ok ??


As morris alluded to above, if the sleeves have been pushed in enough to be flush with the outside of the carb only, air will leak (in abundance) around the throttle shaft and you won't be able to control the idle.

I push the sleeves through until they are just through into the bore and then file them gently back to flush. Easy enough to do.

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 Post subject:
PostPosted: Sun Apr 05, 2009 3:18 am 
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Thanks everyone for the help will check air leeks at bushes. if not the problem would needle and seat in fuel bowls cause a simmalar problem.


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 Post subject:
PostPosted: Sun Apr 05, 2009 12:21 pm 
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west end clubby wrote:
Thanks everyone for the help will check air leeks at bushes. if not the problem would needle and seat in fuel bowls cause a simmalar problem.


no, what you described above is an air problem - you've got too much air getting in somewhere

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 Post subject:
PostPosted: Sun Apr 05, 2009 3:26 pm 
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Simon spot on have elemished all air and are running well thanks for the help, one carb was easy these can be a real pain in the nars.but hopefully all solved. had a view beers fixing this one.

thanks west end clubby


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 Post subject:
PostPosted: Sun Apr 05, 2009 6:17 pm 
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now have a good read through this, and seeif you can set the carbs up properly

http://www.ausmini.com/forums/viewtopic ... =twin+carb

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