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Discussion Starter #1
I’m wondering if anyone here has a 330 or 325 (model doesn’t matter) that has done performance mods? If so what did you guys do for jet sizes for the mods? Also have any of you guys removed the airbox lid and then rejetted it?
 

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Discussion Starter #3
Matty, what springs did you use? Just curious. And how did your son like it?
 

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Not much you can do performance wise with the 325 and 330 engines. Changing clutching would be about all you can do. Different weights in the primary and maybe something with the helix in the secondary.
 

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Matty, what springs did you use? Just curious. And how did your son like it?
I'll have to check tomorrow night when I'm out in the garage. It made a big difference. They aren't bad machines, they just aren't fast and that's about all you can do to change them.
 

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Matty, what springs did you use? Just curious. And how did your son like it?
Green primary, blue secondary. Got it from aaen.

We trail ride.. A lot. He only had that machine for a few months last year and put 500 miles on it in 3 weekends. It's hilly, wide-open and narrow 50" trails. It woke up the lower end and added about 4mph to the top speed. Coming from a 570 with eps I really didn't mind riding the 330. I felt slightly bad since I always had it pinned wide open but it doesn't complain. It's a fun trail machine, it just doesn't have a lot of power.

This year I put him on my old 400ex that I never ride and he's been on that since. He was on a 90 for years up until June of 18, went to the 330 then the 400 this year. He's 13.
 

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Discussion Starter #7
Thanks for the replies guys it’s good to hear what other people have done. There is More things to do on these 330s than people think. I have a big bore on mine that takes it from a 330 to a 414. I’m just trying to get an idea about what other people do to them. I wish I could hear from some guys with exhausts and see what they did for jetting. Or someone who has taken the lid off the airbox and what they did for jetting.
 

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I am gonna look into the spring kit for my 325. Didn't know there was anything you could do. Thanks for the info!
 

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I am gonna look into the spring kit for my 325. Didn't know there was anything you could do. How do I find the spring kit? Can you post a link?
 

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Discussion Starter #10
If you look up Ritter cycle performance and give him a call he will help you out. Rick is an awesome guy and will get you what you need. Depending on how much you want to work on these 330s there is actually a bit of stuff to do to them.
Big bore 414 kit
Port the head
Cam from Ritter cycle
Exhaust
Clutch work
Airbox work
Jetting
Lightened flywheel
 

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If you look up Ritter cycle performance and give him a call he will help you out. Rick is an awesome guy and will get you what you need. Depending on how much you want to work on these 330s there is actually a bit of stuff to do to them.
Big bore 414 kit
Port the head
Cam from Ritter cycle
Exhaust
Clutch work
Airbox work
Jetting
Lightened flywheel
Thank you!
 

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Discussion Starter #12
Well I took the airbox lid off this weekend. It made a huge difference in my top end! A little difficult to figure out the pilot settings but it all worked out. I would say removing the airbox lid and rejetting it was a way more noticeable power increase than clutch work. I ended up with a 42.5 pilot, which is stock, turned 2 turns out. Mine was only 1/2 a turn out because of the high altitude I live at. My main jet went from a 130 to a 150 and is still a little lean at full throttle so I have a 160 on the way. It’s crazy how restrictive the stock airbox is on this thing! Up 8 jet sizes and still going up. That’s a lot more gas witch translates into a lot more power.
 

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Discussion Starter #13
Figured I would update you guys. I hate when someone starts a post and doesn’t finish it. I am still working on the jetting without the airbox lid and the 414cc big bore. The power difference is huge. The 414 was a big difference but I honestly think the airbox lid off and rejetting for that is a bigger difference. I know that rejetting after removing the lid is a bigger difference probably because of the big bore but still the gains to be had there shouldn’t be underrated. So what i have found out is that changing the main jet only doesn’t make a difference on the stock needle if you go over about 150. What I have found out is that the needle taper on these 330 engines is almost non existent and lowering the clip makes little difference because of that. Also, at wide open throttle the needle is still part way inside of the needle jet. So changing the main jet only works until about 145-150 main in my experiences. So what I’m saying isn’t that at wide open throttle the gap between the needle and needle jet is only big enough to flow up to about a 145-150 main jet. If that makes sense. So I researched for a few weeks and found out that a needle and needle jet off of a 1997 Polaris magnum 425 would fit these carbs. I bought both parts and they ended up fitting perfect. The needle has a lot more taper in it. Changing these parts was a huge difference in getting the fuel the bike needed. I also looked at a 97 Polaris scrambler needle because that year used the same bst34 carb that the 330s use but for whatever reason that needle doesn’t have as much taper as a 425 needle. The 500 needle is somewhere in between a stock 330 and the 425 so if you only needed a little more fuel that would be an option. Anyways I ended up at a 180 main jet and the 425 needle and needle jet. With the 180 and the needle clip all the way lowered (richest setting) it’s still lean! I put the bike back together because it has been apart for 3 weeks. It runs awesome but it still needs more fuel so in the meantime I’m trying to find some more needle options. The Mikuni 4 series needles are the same length as the needle this carb needs so I will let you guys know what I come up with. I am also going to take measurements of the stock needle and the 425 needle and I will post them here for reference so if anyone needs numbers off of them you will have them. I really recommend changing your needle and possibly needle jet to a 425 one if you need more fuel. I would guess if you have exaust work on this bike and remove the airbox lid a 425 needle would be just about perfect. It might even work fine with just one of those because these bikes are lean from the factory anyways. If anyone has any questions let me know!
 

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Discussion Starter #14
Also, I did a few other mods to the carb. With the airbox lid off it wasn’t building as much vacuum in the carb. Because of that the slid wasn’t lifting as fast. My bike had a big from about 1/8 to 1/4 throttle because the slide want lifting as fast as it should with the lid off. What I ended up doing to fix this was drill a little hole in the bottom of the slide. These slides have 2 holes in the bottom. One is for the needle to go threw the other is for vacuum. The bike builds vacuum and the hole next to the needle hole comes into play. It sucks the diagram up and lifts the slide. So what I did was drill a hole directly on the other side of the needle to match the hole that is already there. I only did a small hole though, about half the size of the existing one. Most slides have 2 holes for vacuum anyways I’m not sure why this atv doesn’t. I also clipped the spring on top of the carb. The one that pushes the slide back down. I did that so it wasn’t pushing the slide back down as hard. I clipped about 1/8 - 1/4 of the spring off. Both of those fixed by bog problem but also increased throttle response. It slows the slide to go up faster. Pretty easy mods and they worked for me.
 

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Discussion Starter #15
So I figured out my jetting. Just to restate my mods, I have a 414 big bore, uni air filter and the airbox lid removed. My jetting for the mods listed above ended up with a 47.5 pilot 1.5 turns out for the screw, a needle jet off of a 425 magnum, a Mikuni 4 series needle 4J13 and a 160 main jet. The needle is in the middle position. Runs awesome now no bogs anywhere in the throttle range. I messed with the slide in the carb a little for throttle response. I cut the slide spring, about a 1/4 of it off. I also drilled another vacuum port on the opposite side of the existing one on the bottom of the slide. It’s about half the size of the existing one. I’m not sure if it’s jetted perfect but it’s running really good so I’m leaving it. If I revisit jetting I will update you guys. Sometime this winter I’m going to buy a wide band o2 sensor and gauge so I will probably revisit it then to get it perfect. So if anyone needs any more fuel to a 330, 425 or a 97 scrambler 500 any 4 series Mikuni needles will work. It was a lot of work getting it to run right without the lid but man it’s a huge difference. If I had to take a wild guess for someone rejetting with the lid removed and they don’t have a big bore I would guess that the Polaris magnum 425 needle and a 140-150 main jet would work good.
 

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Discussion Starter #17
Marty,
Haven’t been on in a few weeks sorry. The big bore kit was about $600 if I remember right and it did wonders. The bike has a lot more power. That along with rejetting and airbox lid removal are huge gains
 
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