Main jets

[Tompasio]

What size of mains do you think i must have in my carbs.
I have stock airbox and a brand new 4-1.
Stock mains in Europe is 120 for this bike,but she wants to hesitate on high speeds.What size do you have?????

 

[almarconi]

What size of mains do you think i must have in my carbs.

How are we supposed to know Take them out and read the numbers on them.

 

[Suzuki_Don]

Going by the STICKY in the forum it states 117.5 mains for 1983 and up 750s. So the 120 sounds pretty close.

 

[Guest]

i would GUESS that with a 4-1 exhaust & stock airbox you will need to go up one or two sizes from stock with the main (122.5 - 125) and raise the needles one notch.

Again, this is just a guess - do some plug chops & go from there.

 

[Steve]

Hikermikem has the right idea, but I would start with a 125 and not even worry about trying a 122.5.

Which jets you need will depend a lot on how freely the exhaust flows. How can you tell how freely it flows? Loudness is a clue (but not the definitive answer). If it is a very quiet pipe, the 125 might be OK. If it is a noisier, freer-flowing, race-type pipe, you might need 130 or larger. The only way to tell is to install the jets, run the bike and do plug chops. This can be done at a dyno facility or a secluded area of road.

My #2 son's 850 is supposed to have 115s as stock jets. With the quiet pipe that's on there (see pic in sig), I have 120s and it runs quite well.

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