Mikuni Large round n100.604 or small round n102.221 head main jets

[F 18 Driver]

Hello everyone,

Currently I am running 155 main jets… Running to rich black soot on 4/1 exhaust at sea level.

Decided to go with 150 main jets that I ordered directly from the Mikuni

They sent me the small, round head n102.221 jet in the desired size 150

As I recall last time I was in the carburetors. I think it was the large round head n100.604 jet

I immediately contacted mikuni and the person who helped me says the smaller round head jets are interchangeable with the large heads …


However, I want to go with what the engineers designed the bike with weather small or large head main jets

Can someone with firsthand knowledge of the Mikuni Main jet head size kindly chime in and help me…

Thank you for your time and consideration.

F-18 driver

 

[CaptainKyle]

Small is what comes from the factory

 

[F 18 Driver]

Hi Capt. Kyle,

How did you reference or determine that it's the small head size?

The reason I ask is I have done a little more research and have determined that it was the large head size…

I reached this conclusion after exercising my memory of when I replaced the idle jets and examining a few pictures of the block jet assembly 26h–1411a–200–209

Further, the pictures I referenced appear to expose an recess area in the block jet assembly that is meant to accommodate the large head main jet.

I'm not disagreeing with you. I'm just asking for further clarification.

Thank you for your time and consideration.

F-18 driver

 

[maleko89]

Small round was the stock size on Mikuni BDS carbs on the VMX12. I've never seen large heads on a Vmax carb.

https://www.jetsrus.com/a_jet_kit_street/yamaha_1200_VMAX.htm

 

[F 18 Driver]

Thank you everybody,

I stand corrected… The small heads are the correct jets…

Regards,

F-18 driver