I've got an '02 Scrambler 500 that I really enjoy but it's time to add some more go fast to it. Last fall I put an HPD pipe and clutch kit on it which really woke the machine up and I'm completely happy with the results. With that pipe it came with a 157.5 main jet which is 1 jet size up from the stock 155. Here's where i'm getting confused. I'm now going to put HPD's carb kit on the machine which will allow me to remove the air box lid. I've heard this is pretty much the next step before opening up the engine and doing a cam. So I got the kit today and to my surprise it came with a 165 main jet! Does this seem crazy or is it just me? Only 1 jet size increase for a pipe yet a 3 jet size increase for an air box mod?

Thanks for reading.

 

Taking the air box lid really opens up the air flow compared to having it suck air through the lid air inlet! Taking the lid off any other Polaris atv will cause em to run crappy and lean. Go with the jet they recommend since they have supposed to have done all the testing and check how it runs and make sure you check the plug condition. Actually adding after market exhausts only don't require that much of a jetting increase compared to large airflow increases that do require richer jetting . OPT

 

Oh without any hesitation I'll go with the jet(s) they sent with the kit. It also came with a needle, spring, and pilot jet. I was just looking for opinions. I didn't realize the factory air boxes were that much of a restriction. They were pretty adamant about seeing a 2 horse gain by doing this "mod" so we'll see. Thanks for the quick response!

 

Well we have the results... Kind of that is, there's a twist. I store a 2002 Scrambler 500 for a good friend of mine at my house and when he got word that I was putting this carb kit into mine he decided to order up the same one. Now for a little backround on his bike. Like I said it's an '02 scrammy with a full DG pipe and Erlandson clutch kit. His also has a winch and plow subframe bracket which I can only assume makes his bike ~40 or so lbs heavier than mine, right? We've "raced" many times before and my '00 with the HPD pipe and clutch kit has always pulled hard from him. I usually put 1 length on him before the backshift and once it shifts I grab another length and a half. Well tonight we thought we'd test the air box mod/carb kit on his '02 bike first just so we could see if it made a difference since we knew mine was quicker at this point. The install was pretty straight forward and the instructions were dead on. The kit came with a new slide spring, main jet tube, main jet, and drill bit to drill out 2 holes on the slide. It took us about an hour to get everything tore down and put back together. Of course we went out after to test things out and I was very impressed with the results to say the least! With no air box lid his starts up just as it did with the lid and has impressive throttle resopnse. We did get a couple side by side pulls in and from a dead stop I still pull him right out of the hole but now only by 1/4 bike length. Both of our front ends come up hard so we had to try this multiple times before we both got a good "launch" at the same time. His '02 however now comes around me before the secondary opens up and puts about 1/2 bike length on me at that point. I can't catch him after that... Needless to say I was happy for him but wow I never expected such a gain. My turn! Sorry for the run on story guys but I had to share.