Installed 42 pilot and new main jet

[clemsonteg]

So I installed my 42 pilot and 158 main jet today that I got from RMATV (Pro-X is the brand I think). I have an FMF Powercore 4 slip on, uni filter, and the lid on. I put in the 42 pilot and turned the air fuel screw to 2 1/2 turns (it was at 3 1/4 with the 38 pilot). I took out the dynojet 150 (a 165 keihn acording to jetsrus) and installed the Pro-X 158. I ran around for a few minutes on a new NGK plug but when I pulled it out it still looked new so I guess I need to put some time on it maybe to get a good idea of how its doing. I also have a dynojet needle on the 3rd clip.

The old plug was good and black so I know it was rich. I feel good on the pilot circuit, the quad starts easier and without the choke and it doesn't stumble or surge when I ride around and I didn't see the pipes glowing :D so it must be pretty close. The main jet I will try to put some good time in tomorrow to see where I am at, but looking at what most people run on here with a slip on (stock up to 160) I think a 158 should be more than enough and its better than before because when I hit second gear with the new one the front wheels gave me a nice pop that I didn't have before. So what do you guys think?

[f4iracer]

dude you have a huge main jet in there for those minor modifications. I'm running a slip on with a uni air filter just like you and i'm only at a 152 main jet. I can't believe you're running a 158 and you're not rich.

Also, 9 times out of 10, if you take an old plug out it will be black that's totally normal. The key is to have the engine warm and check the plug after running a certain circuit. My plug is always brown or black when i take it out and i've got my quad running perfect.

If you're rich it's black and if yo'ure lean it's white. It sounds like if you're plug still looked brand new that you're probably running lean, because you should definetly have some brown or dark coloring on the plug.

there is no way you're running lean with those jets.

I'm interested to know, did you have to change the needle? I had to change my needle because my quad was falling on it's face anywhere in the mid throttle range. My main is a 152 keihen and it's perfect. My pilot is a 40 and it's also perfect. I"m running 3 1/2 turns out.

[clemsonteg]

I didn't change the needle, it was already on the third clip. The point to me rejetting was to get rid of the dynojets. I will run it some today and pull the plug out and see where its at.

[clemsonteg]

BTW this is the thread I used when I estimated where to start

http://www.exriders.com/vbb/showthread.php?s=&threadid=427686&perpage=10&highlight=jetting&pagenumber=1

And I wanted to see how it would start after it cooled off and sat overnight, all I did was put the bike in neutral and hit the button and it turned right over and started idling.

[aDviSol2y]

Just to let you know, two people could run the exact same set up, but need to run dif. jets. Alot has to do with climate, altitude and sometimes even when those are the same, some bikes just run on dif. jets. Remember, even from the factory, no two bikes are the same.

[honda400ex2003]

I still think you will be close with that 158 but if you only bought 1 jet you may be getting some more lol. I am not sure how the pro x stuff is compared to the rest though. He is pretty low and the filter does make a bit of difference. I ran a 155 in mine with just my t-4 and k&n. He is closer to sea level so he should be right around that unless his fmf or uni does not flow quite as well as i thought. steve

[clemsonteg]

I bought a 152, 155, and 158. I put the 155 in first and it was a definite improvement, I hit second gear and the front end came up on me. Then I put in the 158 and I could tell I lost a little bit so I think its pretty close, I am waiting for it to stop raining so I can go out there and run it around and check it. I think maybe it was close because I am not used to checking plugs but when I checked mine last night it wasn't too far off from the normal picture seen below. Plus most of my running around was in second gear.

http://www.atvriders.com/images/articles/sparkplug/sparkcolors.jpg

[clemsonteg]

Looks like Im gonna break into mine before I do some testing. I was reading some other threads since its raining out and I came across the pic below. When I removed the needle to check its position the washer was underneath, so thats where I left it when I re-installed it, so it looks like I get to pull off the seat and see if I can get to everything to swap it to the top position.

[honda400ex2003]

I dont have a washer on mine at all lol. if it is under it, it will make the needle area richer since it is lifting the needle. steve

[clemsonteg]

Originally posted by honda400ex2003
I dont have a washer on mine at all lol. if it is under it, it will make the needle area richer since it is lifting the needle. steve

I guess I didn't think about it that way, maybe I will just leave it as is and test it out real good then. This is my first carbureted anything so I don't want to mess anything up. It feels really strong and was accelerating super smooth yesterday with no hesitation and no popping on decel so I will play tomorrow and pull the plug and see how it does. I don't have much room but I will try and run it in 3rd as much as possible to get an accurate reading.

[honda400ex2003]

I would def make the call after riding it and checking out the plug a bit. The washers are pretty thin and do not make a huge difference anyway when comparing them to moving a position on the clip. it would only be about half of a clip position move since the washers are .030" i think. At least that is what the ones are on my sled, i have never actually measured these lol. steve

[clemsonteg]

I got out and ran it today in 3rd gear wide open and I got a nice gray/brown insulator so I am happy with it. I may have to knock it down to a 155 when the summer hits and its 100 out, right now its only 65 or 70.

[honda400ex2003]

Great to hear that you got it. What did you come out with for final settings again and how close was I? 158, 3rd position, 42 pilot, and 2.5 turns out on f/a? I like to have an idea of what i said and how it came out, thanks steve

[clemsonteg]

Yeah it was 158, 42 pilot 2.5 turns out and a dynojet needle on the 3rd notch with the washer underneath. I don't have any stumbling anywhere and I think I could probably get away with a 155, but running a little rich is better for me I like to keep things cool and I don't do any racing or anything just playing in the field around the house.

On a side note I also installed my Pro Armor Tether Kill switch and my PRM scoops which completes my upgrade list from my other thread. I will have to snap some pics of it all finished up after I give it a good washing one of these days.