jetting after fitting pod filters

[squishio]

Hi All

Hoping someone can give me a rough estimate of what changes regarding jet sizes I need to make after fitting pod filters to my bike.

Bike - Kawasaki GPZ400R ('83)

Filters - K&N pod's


I'm about to place an order for a load of jets for another bike and thought I might as well get what I need for this one whilst I'm at it.

I don't know what is currently in there but I'm pretty sure it is on it's original jetting so with these filters I imagine it will run very lean as intake will be massively increased over the standard airbox. I haven't had it running (far from it at the moment) but need to get prepared.

So from other peoples experience what kind of jump will I need to make for jet sizing? I'm happy to order a few jets to be safe but just a estimate would be good!

Cheers!
Rich
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Current - Hornet 600, Transalp 650, X140 Pit, GPZ400R
Past - SY125, GT250, GT650, CX400, CBF600, Bandit 600, SL1000, GT250

[temeluchus]

A good rule of thumb is to go up 25% in jet size (ie if you have 90 stock go to 112.5).

depending on the bike you may need to go up more OR it may be less-oh the fun of jetting!

form the manual stock you have 102.5 so in the region of 125-127.5 is a starting point
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Some shite cruiser. Now with guns and FREEDOM!

[squishio]

Cool, very helpfull
I assume pilots will need doing as well, correct?

will the needles need changing or am I good just with the pilot and main?
____________________
Current - Hornet 600, Transalp 650, X140 Pit, GPZ400R
Past - SY125, GT250, GT650, CX400, CBF600, Bandit 600, SL1000, GT250

[temeluchus]

you may need to go up 1 or 2 sizes pilots, but often you can just open the idle screw by a bit for it to run right.

Ideally you'd want a new needle, but they aren't easy nor cheap to obtain and satisfactory results can be obtained with the stock needle usually.
____________________
Some shite cruiser. Now with guns and FREEDOM!

[prawny1]

https://scootrs.com/tech.cfm?tip=tunecarb

this article is pretty informative for carb tuning, it is more for two smokes but gives you a pretty good idea of what to look for when setting things up.