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Swapping a slide carb for a CV

  • Thread starter Thread starter UncleSatan
  • Start date Start date
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UncleSatan

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I'm trying to swap the old slide carb on my girlfriend's 83 GS125 for a CV carb off a newer model, but am having a few difficulties.

The new carb fits ok, it basically pops right in, but getting it to behave is another matter.

The two main problems I'm having is a huge flat spot at around 3k rpm and the idle either is very slow to teturn to normal or will stay at around 3 -4k rpm.

I've done the obvious like cheap for air leaks, but I thought I'd see if you guys had any pointers on this modification before I start trying to play around with pilot screws and what not.

Many thanks
 
Idle problem sounds like an air leak. Is the venturi size the same on both carbs.
 
Idle problem sounds like an air leak. Is the venturi size the same on both carbs.

I've checked for a leak but will have another look.

The venturi of the CV carb is narrower, but I think that's to generate the extra vacuum to operate the slide
 
A few "MUST HAVES"...first!

A few "MUST HAVES"...first!

I'm not sure on the 125's but check to see that there is or is not an o-ring on the intake tube that bolts directly to the head. This is a major cause for most of the symptoms that you are describing. :-s If there is, they get brittle and hard over time and don't seal. It causes the fluctuating idle and flat 3-4k RPM problem, almost like clockwork. Also...make sure that when you're tuning this thing in, that you have both the air filter on (oiled if it is the foam type) and sealed tightly and all the clamps to the air box, intake tube and carb, tight.
 
Hi Dave, the Carb goes straight into the old manifold, and I have replaced the o-ring quite recently.
 
Air filter and box all sealed up? If yes, you're in for a a good carb soak and clean.
 
Yup, but its a brand new out of the box carb, so I'm not sure cleaning it will help.
 
Alrighty then...:-k Have you checked the petcock to see that it is flowing correctly? Is there an inline filter in the bike? Any kinks in the fuel line?
 
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