Actually its the other way around Thats a rich LSN masking a large idle gap.

OK ALL here is how to set your Idle Gap

run the engine for about 2 tanks , make sure its hot DO NOT TUNE AN ENGINE UNLESS ITS HOT !
Pinch fuel line
Listen to how high and how long it revs if it revs high and long you have a rich LSN masking a large idle gap

what you want to hear is the Idle rev up only slightly and die after about 3 seconds.

Use the Pinch method to check your idle gap. Adjust the idle gap then the LSN then the HSN then revisit the LSN


The HSN tune if you have to lean it will affect the LSN , so once you tune the HSN go back to the LSN and revise how it is from when yo tuned it .. if its still the same leave it if its changed then adjust it.

All carbs should be tuned this way regardless of long taper LSN or short taper .

LSN taper will govern revs up to the point it leaves the reciever jet. So it is important to get that right first.

Note a hotter engine will give a shorter pinch rev IE when its hot it will rev up quicker than when its cold . Crank case temps will effect this , thats why you only tune an engine when its hot.

Hope this helps

MM