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Discussion Starter #1
Well I'm modding the body on this Arctic Cat 1990 Ext Special 530 L/C...I'll talk about that later. The airbox has to go due to the modding and we decided to go with pod filters instead. The exhaust is still going to be stock single pipe. I have always tried to jet for altitude and temp based on the stock jetting chart, but usually leaning toward rich. Since we do a lot of climbing it's hard to be spot-on. That said, it has always seemed to run a little on the rich side compared to my other rigs that I configure essentially the same way.

The main problem is I don't know how much pod filters change the intake characteristics at different throttle positions. I'm doing this for logistics (the stock airbox is unbelievably massive), not in an attempt to get more power, but I also know that I need to spend some time figuring out the jetting. So I'm throwing this info out as an attempt to get some guidance on where to start with the needle, main jet and pilot jet. I don't really want to push the bleeding edge of performance, I would just like a safe setup where it can get a little colder out and I won't be in any danger of burning up. I do run premium but let's just pretend and jet it as if I'm running regular for safety's sake.

The stock needle position is already supposed to be 4, as in the 4th richest out of 5. But that is for low altitude and I'll be jetting for the 3000-6000' range. I'm thinking I should start with the needle at position 5 but I may have to consider a new needle.

These are Mikuni VM38 carbs I believe...the round ones. The current needle is 6DH8. So what would be the next richest needle and do you think I'll need it?

The current pilot jet is 25. I usually run the air screw at half a turn to no more than one full turn as it is...so will I need a bigger pilot jet and how much bigger? Or do the pods have any effect at idle?

And finally, how far up do I need to adjust main jets? Like right now I'm running something like 270 main jets for the stock intake and exhaust, based on the average conditions I ride in. Standard Mikuni hex jets. Do I need to go all the way up to something like 300?

So I need advice on where to start, and I know what to do from there. I just don't know how much the pod filters will actually improve airflow, since the exhaust is the same. I'm guessing some but not a whole lot, but I could be wrong. I know some of you have done this kind of thing, so any advice or educated guesses would be appreciated.
 

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Premium Member
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Discussion Starter #2
Any general advice on re-jetting for pod filters would be great. I know I wrote a huge post, hoping for a detailed answer. I figure richen everything and then tune, but how much? If my main jet is a 280 with the airbox, how far up should I start?
 

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you have to get in tune with the whole piston wash thing and test a bit...500` 1000` 2000` in length of run. really though its been my x per eeince that all things equal the filters are worth +3 on the mains....+1 on the needles (unless its a big bore twin) and 0 on the pilots. thats sea level to sea level. i would suspect if your dialed at 5000` or whatever you could change accordingly.
 
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