Wayne Hamilton , Today 05:25 PM
I have a 99 im trying to set up the carb . It has a vm 34 i adjust the fuel /air screw to 11/2 turns out .I set the needle valve to the number 2 setting on the needle I adjust the idle screw to 800 rpm and it's still mid range choppy .

I look at parts list to order a rebuild kit and it says I'm supposed to have a air jet in front but lo and behold I have no air jet .

I again clean carb pilot jet perfect main jet perfect set pilot to 11/2 turns and still running like crap .

it has a snorkel kit on it which is when it all changed . Is there something I'm missing except foe my air jet

 

99 Scrambler 400 or Explorer 400? The 400L series was on the first 94 along with the 94 Sportsman 400. It calls for an air jet but I believe it's fixed as I've never seen a replacement in any kit, even the best kits around Shindy.Shindy Products, Inc. - ATV Replacement Parts If you need a kit. Here's the carb section from the manuals that may help also if you don't have it.https://www.google.com/url?sa=t&rct=...U2gGlaHJWSIlbA You can drop the needle clip to the 3rd position on the needle and see if that helps. If it's worse then drop to the first position. If it's still choppy you may need to change the main jet. Before you do you can increase from 1.5 to 2 turns out on the air scew and see how that does. Or in from 1.5 to 1 turn out while playing with the needle.Plus the air box and filter need to be on for correct adjustment.

 

It is a 99 scrambler

 

I pulled needle and set at number 3 and reinstalled now I can get about 5300 rpms out of it but still a bit choppy midrange to 3/4 .
wondering if I need a new pilot jet or beings the snorkel is on it maybe open up the air fuel a little more to see if it smooths out
thanks in advance

 

1 turn out min to 2.5 turns out max on the air screw. If you can't find a happy medium between the air screw setting and needle clip adjustment then you may need to try different size pilot and main jet. If the air box inlet is snorkeled then yes that can take a little experimenting to get it right. If you don't have a shop close by Jetsrus has the oem and generic Mikuni jets. Plus they have jet kits depending on model. This is for a 99 Scrambler 400.https://www.jetsrus.com/a_jet_kit_at..._1997_2002.htm

 

What is the stock jet sizes main/pilot there are no stamp marks or numbers on the current main jet or pilot jet

 

Should be marked on the top on the main,side on the pilot jet,but parts breakdown shows a 230 main jet,35 pilot as stock. 230 imo was too much in some cases as the other 400s had a 200 or 210. But Polaris knew how the Scramblers were going to be treated also..This may help with the markings.https://jetsrus.com/FAQs/FAQ_identify_that_jet.htm plus sometimes a magnifying glass if the markings are faint.

 

Too rich = down size
Too Lean = up size
or vise versa

again thanks for all your input it really helps

 

Bogging,wet or dark plug, then it's too rich.Down size on the main jet.Hesitating,plug looks lighter than the tan to medium brown that it should be, the jetting is too lean. The 35 pilot jet is usually not the problem. Plug chopping is a good way to tell. Get it warmed up and at a high speed kill the atv and stop asap. Let it cool off and check the plug color.