My jetting problem...

[RangerRick]

I was wondering what I need to do to the jetting on my fourwheeler becase I think somethings wrong.The first time I start it up in the day or if its been sitting for awhile it pops and dies for like a split second and then keeps running and sometimes when you first start it and give it gas it quits.Right now I have a dynojet kit in with the 165 main jet and the dynojet needle on the 3rd groove from the top.I also have in a 42 pilot jet and the air/fuel screw is turned out 3 1/2 turns.I live in northern NY and the elevation is 257 feet and the temperature has been getting warmer and right now at 10 something at night the temp is 58 degrees.I might have went a little overboard with the info but I wanted to make sure I could get my jetting spot on.:D Thanks.

[RangerRick]

Oh I forgot to say I have a full DG alloy exhaust system with a k&n filter with an outerwears and uni air vents in the top of the airbox.Oh and the choke is removed.

[GPracer2500]

You can almost never give too much info about the quad or the environment when it comes to jetting. It ALL makes a difference.

I'm not really sure but if anything it sounds a bit fat (rich). Your elevation and temperatures DO lend themselves to larger jets but try going 2 or 2 1/2 turns on the fuel screw and maybe one size down on your main and see if that helps. Also, as an alternative to changing the main you can try removing your airbox lid alltogether. Lid on or off (even a vented one) can be a quick and easy tuning tool. I'd still lean out the fuel screw a bit though.

Those are just guesses but if your at a loss it's something to try.

[RangerRick]

Im gonna try what you said tommorow.when I turned out the air fuel screw to 3.5 turns i was just doing what the dynojet kit said to do but Im sure they could be wrong.Also my next size down main jet is a 160.Will that be fine?Before I change the main tho I will try taking off the lid but I ride at a sandpit alot so dont I need it?I do have an outerwears on my k&n but I dont know....Thanks for your advice though.

[NCexRider]

I was running a DJ165 with no airbox lid, then I decided to put my lid back on with those uni filter vents. When I did so I started fouling plugs because I was too rich. I backed down to the DJ155 and I'm pretty much spot on now.

[GPracer2500]

A dynojet 160 should be about the same as a Keihin 178 which sounds a lot better than the about 185 (Keihin equivalent) that you've got in there now.

In my experience K&Ns (even with Outerwears installed) don't filter adaquitely enough in dusty conditions. I ran a K&N w/ Outerwear for years on my 400EX with no perceptable issues (in dusty desert conditions). However, when I recently rebuilt the engine the cylinder and intake valves showed signs of fine particulates making there way through. I run a UNI now. They maybe flow ever-so-slightly worse than K&Ns but filter the tiny stuff better. Anecdotal evidence all over the internet supports the validity of my experience.

I run a well oiled UNI in dusty conditions with no airbox lid with confidence. I do clean it almost every ride.

I suggested removing the airbox lid simply as a quick way to check your jetting (primarily your main). If you take the lid off and it runs better, your jetting is too fat for running with the lid on. Then you know that if you want to run with your lid you need to change the main. That's what I ment by using the lid on/off as a tuning tool.

[RangerRick]

Alright thanks for the help so far.

[jsmith2232]

I had the same problem, the pilot circut was too rich. warm it up turn you idle up and try turning in your fuel screw until it starts popping and go between there and 3.5. I ended up at 2.5 turns out at 2 it idled fine but on a decel it would pop a bit so i went .5 more and now it runs great.

[RangerRick]

OK I just finally got around to doing it because I noticed it was leaking gas from somehwhere on the carb.I rejetted it with a 160 main and I turned the mixture screw out 2.5 turns but when I went to start it it would start and die.Well once its back together as you all already know the mixture screw is impossible to get to so I ajusted the idle screw instead for now and it fired up.The only thing is when I chop the throttle quick it dies for like a complete second or maybe more and pops or something.What do I need to do next?Should I take it all back apart and try 3 turns out on the mixture screw and then readjust the idle?Thanks again.

[quadrider400]

I would remove the choke.. and change the pilot jet... As I recall it goes to a 42... been a while...

Also I would try removing the prefilter.... that was a big problem with mine ... now i just run the K&N with the lid off...

just my .02;)

[jsmith2232]

Try taking your airbox lid off and stab the throttle, if this helps then you are running too rich on your pilot circut if it makes it worse then you are running too lean.