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Discussion Starter · #1 ·
I got the sled blown up. As a result I checked the main jets on the Mikuni flats and to my suprise there were 350 mains installed! Stock jetting should have been 440's. Speedwerx says 480's is where it should be, but no info on whether or not to raise the needle jets. Has anyone ever used the Speedwerx twin pipes? They seem to be fairly rare. Is it even possible for someone to jet the sled over 100 jet sizes too small? Wouldn't you notice the sled struggling to accelerate due to lack of fuel or are they that much faster being this lean? He told me the carbs were bored, but then again wouldn't you give it more fuel to accomodate the higer air flow? Please note the air box is also removed and high air flow filters/screen sit on the back of the carbs.

Just wondering if someone else has used the Speedwerx twins or any suggestions on how to get the sled to be reliable. Performance is great, but I don't want to be left tearing this sled down again when the snow flies.

Thanks for your time,
 

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well if the sled is running the pilots should be fine if it idles and starts some what with in a few pulls, but for the main jets start out where speedwerx stated 480 mains. itll get you in to the ball park then you can fine tune it with plug chops to see if your too rich too lean or just about perfect. its always better to run a tad richer then it is a tad leaner. if the carbs are bored over you may have to go to 500's to accommodate more air along with the pods. but start with 480 and work your way to tuning it in. that's the best advise I have for now
 

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Mr Top Whore
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Welcome to Dootalk! Where are you from and where do you ride the sled? Stock mains for the 03 800 should have been 430 and a P-0 needle jet. Needle setting should be 3 from the top. And it does depend on if the DPM is hooked up. Also running the unfilters and twin pipes. I would start off with the suggestion of Speedworks.
 

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Discussion Starter · #5 ·
Can someone please tell me if the altitude compensation is currently hooked up? The guy that had the sled before me said that EZ jets were installed. In the pictures the red circles are where I would assume an adjustment could me make to reduce the fuel if I was in the mountains. However this adjustment will not move at all. It does not matter which direction I try to move the dial. Please note that the red circles point to a line that goes towards the bottom of each carb. Blue circles are where they actually connect on the bottom

Motor vehicle Automotive engine gasket Auto part Machine Engineering

The yellow circle is another point of confusion. Why does only on carb have a line coming off of it. Is this the line that should go to the airbox and the other one simply fell off.

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Thanks,
 

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Those would be power jets so no your altitude compensation would not be hooked the lines for the power jets should be connected to the bottom of the bowls and those lines that go no where I do believe are only vents for the carbs because the altitude comp is off power jets are a 3/4 to full throttle that's why the mains are so low Those adjustment knob hold the jet completely unscrew it and clean them Go on thunder power jets website and find or email them for a set of instructions
 

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Discussion Starter · #7 ·
I think you hit the nail on the head. According to their website you can reduce the main jet 20 - 25% because the remaining needed full from 3/4 to full throttle comes out the power jet on the top. This makes complete sense. However, I'm not sure about the term "straight jetting". If someone could fill me in on that I would appreciate it.

Bottom line I will jet the mains at 380 and lower the needle jet clip (thus actually raising the needle jet) one setting. Check plugs, rinse and repeat.

Also, to answer a question earlier I ride in the Midwest.

Thanks everyone for your input!
 

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Hi, I am from Iowa too! Buffalo Center to be exact. I have a 02 mxz 800 without the dpm. I am running the stock air box, boyesen reeds and stock exhaust with a can. Around here I run a 500 main jet. My needles only have one slot. I take it out west and get up around 11000 ft, I run a 440 main. You will be flowing more air with your setup so you should be jetted down. I would say that 350 is way too lean. Good luck
 

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Check the head for compression ratio also, if he was running race fuel or anything higher then 91-93 octane that low number reflex's that also.

But with most of the 800 doo's I have built at sea level were running around a 480-500 mains with no DPM. My polaris 800s would run a 440 main and my cats where in the ball park between. My full on race 800 mod motors I was down around a 380 main with twins on race and my D&D 720 race motor on pump at sea level I have had to jet as much as 520. So i would check into that also on what head he is currently running.

Pipes work great if you know how to keep them in tune. Also depending on where/how high you ride up to see if the pipes can take the high altitude, I have never really seen speedwerx build high altitude pipes besides the few odd ones with Cat and even then I dont find them to work that great above 5000ft.
 
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