What’s the correct pilot jet size for a kz 1000 st

Hi what’s the correct pilot jet size for 1980 kz 1000 st with k and n filters and 4into 1 pipe ,with race can , it has 28mm mikunis,

Armahammer wrote:

Hi what’s the correct pilot jet size for 1980 kz 1000 st with k and n filters and 4into 1 pipe ,with race can , it has 28mm mikunis,

Not to sound sarcastic but the right size is the right size, and gives you the best performance. The forum will need more information. 

• pilot jet size
• main jet size
• needle jet size
• jet needle size
• slide cutout
• current plug conditions

Way more involved than jet size. A standard rule of thumb with K&N pods is install air corrector Jets, return all Jets to stock size and go up 2 sizes on the mains. 

What is the stock size at the moment it pops and bangs on the overrun and have the air screws turned down to 1 turn out , plugs seem ok at that colour is brown to cream,

Stock size is 15

I'd try 17.5 to start.
Steve

I can’t make out the numbers on jets very worn I will try some 17 .5s thanks guys ,

Back fire on deceleration is a lean condition. Could be air leak at the carb holders. Plugged passage in the carb. If I remember correctly 15 pilot 102.5 mains. You really need air corrector jets to limit the lean off idle caused by pods. 

Armahammer wrote:

I can’t make out the numbers on jets very worn I will try some 17 .5s thanks guys ,



 

The numbers won't be worn, just very tiny. Get yourself a 4X loop to inspect.

Sometimes China jets don't have pronounced numbers like proper OEM Mikuni/Keihin jets (Japanese) so they may even be no-name brands in the carbs installed by a PO.