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 Post subject: carb tuning
PostPosted: Sat Mar 25, 2006 7:59 pm 
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848cc
848cc

Joined: Thu Jan 20, 2005 1:22 am
Posts: 267
Location: Perth
Need to tune my SU 1 1/2 inch carb

Have tried but finding difficulty cos when airfilter is removed revs go down so hard to set idle speed, also is there a simple way to set the mixture - how do i know when it is right :?

Thanks

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PostPosted: Sat Mar 25, 2006 10:12 pm 
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Bimmer Twinky
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Posts: 8606
Location: Brisbane
ok,,,when the air filter is removed & the idle goes down then the mixture is probly allready too lean

the idea is to adjust the mixture at the jet (under the carb, that black thing that sticks down) there`s a nut just above it that you can turn, up is lean & down is rich

wind it down some & listen to the idle,,,as you`re winding it down the revs will probly rise a tad , then as you keep winding down the revs should start to drop again (going rich) so wind it back up till you find the middle (sort of) if you can wind it up & down & find the happy middle , IE: where it`s at it`s highest idle, then you`re close, but still a tad lean, find the middle highest point of idle & then start winding it down slowly till the revs just start to drop only a tad, then that`d do you , go for a spin & see what it`s like , if it`s still yukky throughout the rev range under load situations then aa good tune is probly needed & maybe a change of needle &/or oil in the dampener &/or dash pot spring etc etc etc,k,,see what your spark plugs look like after a 20 min drive & report back their colour

anyways, that is just a sort of rule of thumb thing for you to have a go at

have fun just don`t leave it lean, a tad rich is way better than a tad lean

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 Post subject:
PostPosted: Sat Mar 25, 2006 11:01 pm 
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848cc
848cc

Joined: Thu Jan 20, 2005 1:22 am
Posts: 267
Location: Perth
Thanks for the comprehensive yet simple to understand tips. I will give it a go.

Local mechanic used to work for SU so I might give it to him for an hour see what he can do if I get no joy

:)

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PostPosted: Sat Mar 25, 2006 11:04 pm 
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1360cc
1360cc
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Location: Geelong, Victoria
All I can say is good luck and atleast you only have 1 carb! 8)

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PostPosted: Sun Mar 26, 2006 5:18 am 
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The TIG
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Location: Victoria, BC, Canada
On the carb I had on my 1000 there was a small button on the bottom of the carb that you could push up when the car was running. You adjust the mixture until the engine speed does not change up or down when you push this button.

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