Wondering if this forum can help me with Jetting an almost bone stock 2003 660R
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Thread: Wondering if this forum can help me with Jetting an almost bone stock 2003 660R

  1. #1
    Stock, ready to MOD jason9922's Avatar
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    Dec 2018

    Wondering if this forum can help me with Jetting an almost bone stock 2003 660R

    So I met someone online in a Facebook Raptor 660 forum who because of where he lives where the atv sound laws are so strict and he said the sound of his muffler scared his son he was looking to trade his chrome flawless looking Duncan Racing Fat Boy 4 muffler (which they sell rebuild kits for and they come apart very easily to do so) for a bone stock raptor 660 muffler. But obviously he wanted to trade for one that was clean like his. Many people tried to trade him but there's were rusty etc. Myself wanting a slip on and love loud traded with him as my Raptor has very low hours on it and has been garage stored pampered before I got it my muffler looked new. So we trade. All went smooth. I put a new gasket in where the stock muffler connected.

    I completely rebuilt my carburetor with Mikuni jets before this with my air screws set at 2.5 and 2. Where I'm at elevation of 500 feet location near Saginaw Michigan area code 48706.
    My problem - I called Duncan Racing and as I'm sure some of you already know the guy who runs Duncan is a total asshole. I asked him for jetting tips on a stock air box yes with snorkle, only thing different is the dual intake Uni air filter. He said "I don't believe in slip on pipes they don't work I don't know what to tell you about jetting. This was after he told me to download the instructions for the entire fat boy 4 exhaust system. After I told him I only had the muffler he turned into a prick. "oh your the guy who asked about buying just the header and midpipe like a month ago? Oh I'll reply to that email when I can".

    So now I have no clue what jets to use. When I start it which it starts and idles perfect. Any punch on the throttle it pukes. It's not the parking brake or nuetral switch. I have done both mods as described here in blue Trax. After I started talking to the parts guy at the Yamaha dealership he said just removing the snorkle off the airbox would make you need to reject.

    So can someone who knows about jetting one of these beasts please offer some advice. I'm sitting bone stock with 22.5"s and I whatever stock for the two carbs mains are " I don't remember right off hand".

    If you purchase the entire Duncan exhaust there instructions are to up the jets to like 155 and 178 or something close using the 4th needle clip.

    Well the spark plugs isn't the easiest to get to so if someone could give me advice on how to proceed I would so appreciate it. I want to ride this quad so bad and it just snowed here about 2 weeks away from the river behind me is going to freeze over. I bought two rear tires with stud slots for the ice. Can't use them though if this things gonna choke and puke when you give it has. I would very much appreciate help fellas.
    I have this posted in another forum and received some great answers from good guys. Just not many responses. Was just wondering if anyone over here had any different thoughts.

  2. #2
    Supporting Member
    Wreckless's Avatar
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    May 2008
    No matter what you do, you will need to confirm it with jetting runs and pulling the plug. If you don't want to mess with jetting you made a bad choice trading. I also don't like slipons, they dont do much and they make you go through the whole jetting nightmare for minimal gains. I would not even mess with it as a slipon. I would put your effort into getting the mid and header pipe. At this point you are in uncharted waters and jetting work is needed and it sounds like you don't want to put the work in. Also, even if you get the mid and header pipe, you cant just throw those jets in on the manual and call it a day. Michigan is at different elevation then CA and those jets that are suggested need to be verified after you make the change.

    Coop we miss you brother..

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