We all change the main jet for better performance at high/full speed, but why is there no need to change the needle jet Because that is the part of the carb. where the fuel goes through and that stays the same size.

By the way I am very pleased with my concentric 626.
cutaway no.3 and now trying with a bigger main jet. (250)

Thanks
John

email (option): john.kater@chello.nl

Hi John..Increasing jet size won't in itself provide more performance...just more fuel in the 'mixture'(and probably less performance). The carburettor settings for the engine are designed to provide the correct fuel to air ratio...Main jet size is calculated initially to suit the capacity of the carb to pass air when fitted to that particular engine and if the engine is standard no change in jet size should be required.....
In the case of a 'Concentric' carb they perform much as a 'Monobloc' and use the same jets. So, select your main jet size from the 'Monobloc' spec. sheets...It should run OK on that....Ian

email (option): ian@wright52.plus.com

The needle jet's cross-sectional area is always larger than the main jet.

email (option): sales@victorylibrary.com

Panic, I was not aware of that. It is the first time I alter something on this carb. and start thinking


John

email (option): john.kater@chello.nl