clw

Member
Dec 29, 2000
239
0
2 questions:

1. With no other changes besides displacement, will a larger engine require leaner, richer or the same jetting as a smaller one? Example; a 250 and a 300 by several brands are sister motors with many shared parts.

2. Keihin jet numbers; are the size increments based on flow (area) of the orifice or drill bit size (diameter)?
 

MikeT

~SPONSOR~
Jan 17, 2001
4,112
11
Originally posted by clw
2 questions:

1. With no other changes besides displacement, will a larger engine require leaner, richer or the same jetting as a smaller one? Example; a 250 and a 300 by several brands are sister motors with many shared parts.


2. Keihin jet numbers; are the size increments based on flow (area) of the orifice or drill bit size (diameter)?


1. Although they appear to be the same parts the internal jets are different and the carb diameter is different.

2. Don't know that one...
 

snaggleXR4

Member
Aug 5, 2001
309
0
Hello,
About the bigger motors, it's hard to say. Generally I would say that if you took a bike, put in a big bore kit, you would want to go richer. However, You always have to increase airflow at the same time. That's where the bigger carb diameter comes in as mentioned above. As for the jets, I'm not sure what the numbers really stand for. I do know that the bigger numbers have bigger holes. So a 162 main jet would run your bike richer than a 160 mail jet.
Maybe someone more knowledgeable can help you with more. Good luck.
 
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