GS1000 mixture via air screw

[kamakiriad]

Hi, thanks for great forum. Wondering on bit of help please. I've bought and refreshed a neglected 1978 USA GS1000 - valve clearances, filters, points, cleaned carbs, new fuel screws etc. Problem is running rich/black plugs on all carbs. Using a colortune, the only way I can get the bike to run well and colour correctly just off yellow/rich, is with fuel screws a whisker off seated and air screws way out up to 2.5 even 3 turns. If I touch fuel screws even to 1/4 turn from seated the mix will overly richen. Float heights are good and I've checked fuel levels in the bowls after sitting primed, and all good. Pilots are standard size and choke plungers work well and shut off okay, although these were first thing thought of as culprit (any ideas how to check without removing carbs?) . Coils are originals work okay. Just concerned running with air screw so far out will affect mix further up throttle. Any help much appreciated. 
Jim

Edited October 19, 2023 by kamakiriad
Shortened

[PaintItBlack]

Running that rich at idle makes me think the air passages in the mouth of the carb could be blocked, or possibly a previous owner fitted air correctors in them, to run pods , do you have the airbox fitted ?

the very fine tips on the fuel screws , the ones that fit underneath the carbs can break off , causing problems, but you say you replaced them 

Edited October 20, 2023 by PaintItBlack

[kamakiriad]

Hi, thanks for reply. The standard airbox is fitted with new filter and yes- new fuel screws. Thankyou- that's good point, from what i can remember - unless the correctors are installed further into air passage - I didn't see any correctors fitted, but will check again tonight. I'll also double check the pilot jet size.

Jim

 

[BigT]

You should also check the holes in the carbs the fuel screws fit into.

People often overtighten the fuel screws, enlarging the holes