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Carbs

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Cujo

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Good Morning,

Having trouble with a set of SU's. To get a mid scale on my UNI-SYN I have to have an extremely high idle. I have just rebuilt the carbs but the rebuild kit (from a well known distributor) came with a jet/needle combination that had different needle shape - almost no taper to it. But seeing as it is matched with a new jet I figured that should not matter. End result right now is a very high idle to get correct air flow and carb balance.

Thoughts?

Thank you
 
Assuming both carbs are balanced, just turn the idle screws down in equal increments until the idle is where you want it.


w00t! My 500th post! :smile:
 
Have you successfully used the unisys before? I'm not sure if you are asking for instructions on carb adjustments or the tool?
 
Have successfully used before (even repaired based on info found here as it is the China model)so carb advice is what I am looking for

Thanks
 
not that I can find - all new gaskets etc. Any suggested areas as I am more used to the Stroms on my 6.
 
That leaves the car unresponsive to initial throttle input - like a miss but the timing is bang on with all new parts and gaps are all correct
 
Throttle shafts are often the source of vacuum leak and inconsistent idle and are typically well worn.

Something to check.
 
Gerard said:
Throttle shafts are often the source of vacuum leak and inconsistent idle and are typically well worn.

Something to check.
Click to expand...


What Gerard said.

Also, I check the needle to see what the numbers/letters are on it, that could tell you alot.
 
Cujo said:
Is the only solution then a new set of carbs?
Click to expand...

If it is the shafts being a bit loose, probably not. There are several sized replacement shafts that can be used but it may require reeming the body which is often best left to professionals.

Can you wiggle the shafts at all? Best to try with everything disconnected, but can you see if there is any play in them as they sit right now?
 
With engine running spray a bit of starter fluid at the exterior throttle shafts where they go into the body. Increase in rpm, vola leak.
 
No play in them in a circular motion - just an ability to move the shaft left to right quite a bit. But when I tried propane around the shaft (as suggested by Moss) there was no change in engine idle or exhaust note - nowhere created that.
 
No, you do not need new carbs, something stupid is wrong.

Butterfly should prevent the shaft from moveing right or left. Look inside while moveing the shaft. What's loose?
 
You said"To get a mid scale on my UNI-SYN I have to have an extremely high idle."

I think you need to close the dial on the Unisyn in. The bit in the middle can be turned in to enable carbs that don't suck as much as ZS on TR6s do to register.

Peter C
 
Like Hap said. He's the man.
 
A little side play may be normal if the butterfly is not closed all the way. The movement is usually axial when they are loose, but you can't really tell when they are mounted with the linkage in place. The linkage will limit movement.

However, your other test seems to indicate that's not the issue. Hard to say what it is without knowing your entire setup procedure.

The first and most important thing that is often overlooked is getting the butterflies in exact sync. Even if it's only a little off, it will get one opening way ahead of the other. You should look into the throats while pulling on the throttle cable and observe piston rise. They should be identical from the instant the start lifting. Make sure you started with 12 flats down to begin fine tuning mixture and make sure you set both idles screws to maintain identical piston rise with throttle input.

What needles did you get?
 
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