What Carb Jets Do I Get??

Gettin a new set for my 650 and I want to get the most suited to my 4 in to 2 with straight through mufflers and I'm planning on getting a high flow air filter.

The mains I have currently are 110/45's but I know little to nothing about them.

Any suggestions?

 

The change to a K&N filter would reqire one jet size increase. So that would mean go from a 110 to a 112. I am not sure about the straight mufflers. A 4 to 1 header usually takes 2 jet sizes. So if you need to change it would only be one size. But that may not be needed witht he crossover in the 2 to 1. I will let some others who may have done this chime in with their expertise.

 

I was always told to start with the following formula .

1 - more air = 1 size up on main
2 - more air and exhaust mod = 2 sizes on the main and 1 size on pilots
3 - more air and straight pipe = 4 sizes on main and 2 on pilots

This only gets you in the ball park

REMEMBER , change only 1 thing at a time , makes it easier to trace mistakes .

I'm running pods and 4 into 1 with drilled baffle and I have 43 pilots and 118 mains . Remember that hitachi carbs go up in increments of 2 on jetting

 

Does the increase 112 jet size apply to pod filters as well?

 

No. Pod filters would most likely require 2 jet sizes and maybe a change in the main needle also. I don't have any real world recommendations for pod filters. Most have had trouble getting them to run without flat spots. Main reason being that the pods don't incorporate a velocity stack. If you look at old pics of these engines setup for racing you will notice a bell shaped tube attached where the airbox boots would be. These are velocity stacks. Main problem with using them on our bikes is that the frame is in the way on the outside carbs so you can't even attach them.
You can search posts and threads with a member who goes by "pigmouse". We got his bike running and running well with pods. He is the only one other than Dean in Arizona and Steve in Dallas that I know of who was able to get their bike running well with them. Dean bought his bike from a friend who did the pod work so I don't know if he would know the setup.
In short , pods should be taken very seriously as they require a lot of trial and error to get right. Most have to run their bikes through many plug chops or pay for a dyno run to see what is needed.

 

Thanks guys... will let you know what I decide on and how it goes

 

Never go more than one size on the pilot jets. No matter how much air flow, 2 sizes will cause too much fuel and bogging down on take off.

I run pods and a 4 to 1 pipes with a fairly unrestricted muffler.

My carbs only have a change in (+1) pilot at the moment. Using standard jets it still runs fine and rips the arms out of the sockets at all revs.

The only trouble with the stock mains is that it runs too lean at higher revs so I'm restricted to short bursts rather than long hauls. I am getting a collection of jets together to rejet to better suit the system but with yours Alive, I would probably only go up one size mains and see how it runs.

Rejetting is a fiddly task and requires quite a few WOT plug checks to get it right.

The following are the guidelines I use from XS11.com. I have found them to be pretty spot on. Just bear in mind that they are guidelines for Mikunis so the jet sizes are 2.5 rather than 2 increments, but the info is just as relevent.

Cheers

HG

 

Cheers Goon.... Decided to only go up 1 size anyway