Weber IDS Butterflies

[chris68]

Hi All,

A quick question about IDS Webers.

I'm just replacing the Teflon bushes on the ends of the throttle spindles and noticed there are two tapered notches on the side of each butterfly.

Can anyone please confirm which way round the butterflies should go? I appreciate the notches should be adjacent ports on the carburettor throat but should they be visible from the underside of the carburettor? - I'm wondering if they were fitted the right way round at the last rebuild.




Thanks,
Chris

[1QuickS]

First of those I've seen on Webers, The Zeniths and Solexes have them.

Notches should not be visible from the flange side (bottom.) Also, the throttle shaft is not centered in the bore; there is a .5mm offset. Weber throttle plates are stamped with "78" which denotes the throttle plate ellipse angle and the "78" should be located on opposite side of throttle shaft from where the progression holes are located.

[chris68]

Hi Paul,

Many thanks for the advice.

The other side of the butterfly has 79o30 stamped on it and the numbers (not the notches) were visible from the underside of the carburettor when I stripped them. Hence, it looks like they were assembled correctly.

Oddly though, the numbers are on the same side of the throttle shaft as the notches, ie the nubers are behind the notches on the butterfly. With the butterflies inserted correctly (notches facing up and numbers facing down) both the notches and numbers will be on the progression hole side of the carburettor throat. Maybe it's perculiar to this early IDS carburettor??

Thanks again for the information.

Regards,
Chris

[chris_seven]

These are Dellorto Throttle plates and are not correct for the IDS.

79deg 30minutes is the throttle plate angle which is incorrect for the IDA and the IDS.

The throttle plate angle should be 78 degrees

The IDS and IDA both use the same part number throttle plate so there is no difference between the two types of carbs.

The difference in angle will affect initial progression but it may not be too serious.

I have plenty of the correct new Weber IDA/IDS throttle plates and it may be an idea to change them.

[chris68]

That's interesting .....

I've always had issues with smooth progression and this might be the culprit.

Regards,
Chris

[1QuickS]

The plates you have will close below the progression holes 1.5 degrees more than the correct 78 degree plates would, the result is there will be an initial lag from cracking the throttles open until fuel from the first progression hole is delivered. I also make throttle plates but another way is to buy some from PMO.