Jetting - plug looks good, thought it would have more low/mid

[qc dsm tsi]

I have an 06 400ex that I just rebuilt over the winter. Before this it was bone stock with stock jetting.

Installed JE 10.6:1, Motoworks slip on, open airbox, Hotcams stage 2.

I went off this post (http://www.exriders.com/vbb/showthread.php?s=&threadid=445695&highlight=jetting+placement) closest I could find was 42 pilot 170 main.

Was able to break it in with this, it was close. Since the needle is non adjustable, I have a washer under it, richen it up. Then swapped out 170 for 175. Seems to run and pull great top end. Honestly it pulls miles better than stock obviously. It just seems like it should have a little more low/mid. The plug looks good. I am at 700ft elevation.

Should I try a 40 pilot?

Thanks

[Zakradu398]

I have a 87mm bore (407), 11:1 wiseco, powerbomb header, Yoshi slip on shorty, hotcam stage 2 and 1200' MSL. I got a 170 main and 42 pilot

[bcleveland]

Almost all engines will pull better on the low side when they are a tad rich. And pull better on top when they are slightly lean. I finally set mine up to where when I first stab it or lug it hard it blows a puff of black smoke out. I had tried it with a leaner jet and the plug was some cleaner but hurt my low end. Maybe this will help you some.

[JOHNDOE83]

Just so you know, Those jetting charts in the link are "good" \but they dont have the correct information on how to check a plug, they also do not tell you the correct way to jet for main jet.

It will not pull harder on the low end a tad rich and it will not pull harder a tad lean on the top. It will pull the best and be the fastest with the correct amount of fuel.

Please read the jetting info with video thread a few down from this one.

This thread. use the links provided. its a long read but read the whole thing. http://www.exriders.com/vbb/showthread.php?s=&threadid=500430

[bcleveland]

My friend with all due respect you are flat wrong. Now if its a stock trail rider that all you want is smooth factory power I agree with you. But if your wanting to tune for performance then I am 100 % rite. If you have ever spent much time a round a dirt track or a mild drag car then you will see every single one of them load up on idle. Why? To get the full amount of torque and pull off the bottom. Always tune for torque and a strong smooth curve. The only people that will be impressed by big hp numbers and bad torque or torque curve is friends and the un educated. Ok another example and here's one you can see although it is dealing with alcohol you can see this example better. Take a top fuel or funny car or any other higher end drag car do you see that white mist coming from the exhaust that's not smoke it's unburnt fuel. Now if engines run better when they are tuned to be stoichiometric ( chemically correct) then every one of those guys and all other forms of motorsports are doing it wrong. And when I say lean on top that's a fine line but as engine rpm increases volumetric efficiency drops . Air speed goes down so which means your carb has to lean its self out to match this. So at the very least a tad lean carb will be better than a tad rich. When your tuning for true performance not ripping the backyard .

[JOHNDOE83]

I highly doubt the biggest jet supplier in the world is wrong.

Anyone willing to try it for themselves would see it with their own eyes.

You said I havent been around a drag car? or havent had much time at a dirt track? You need to double check because well.....I do it all the time.

Please read the FAQ section here www.jetsrus.com read the WHOLE thing and actually try it.

[bcleveland]

No bud I asked. I don't know you or your life by any means. They may be the biggest jet supplier but there are tons of carbs sent out everyday to be made better by a specialized machinist. If I look at it the way your saying then there would be no need for a specialist of any kind. The manufacture already has it the best it's gonna be. Hey don't take my advice it's ok I'm a big boy. Just keep tinkering till you get it then ride the crap out of it.

[JOHNDOE83]

Yes sir, but no machinist can machine a carb to have correct jetting, No flow machine can predict the actual jett number.

Tinkering till you get it right is not the right thing to do at all and going up in small incriments isnt right either. If you havent tried to jet a ATV with the correct method "in the links I provided" then youll never know your ATVs true potential.

The manufacturer DOES NOT have the atv jetted correctly, It is mass produced and jetted so it can be sold in Florida at sea level or sold in a snowing mountain town and still start and run halfway decent.

Please read the jetting with video thread a few down from this one "also in the link I provided" to try and better understand what is actually happening.

And FYI on the plug, if you havent physically cut the threads off you cant see the main jet on your plug. "true story"

[JOHNDOE83]

And BC, just so you know.

I personally built this by hand and its built strictly for drag racing.

My cr250/400ex hybrid drag bike.
http://i953.photobucket.com/albums/ae15/johndoe83_2010/CAM00257_zpsc165e216.jpg (http://s953.photobucket.com/user/johndoe83_2010/media/CAM00257_zpsc165e216.jpg.html)

[bcleveland]

That's nice I don't doubt you I just don't agree and that's ok. My 2 stroke knowledge is crap I will be the first to say. But don't typically 2 strokes twist up harder on top side and absolutely scream when slightly lean. And that's why so many people stick them or burn them up. I have done 2 like that myself run o so good then blah and it was stuck

[qc dsm tsi]

Back on topic please.

[ben300]

Have you adjusted the clip on the needle?

It may need moved down a notch

[qc dsm tsi]

Originally posted by ben300
Have you adjusted the clip on the needle?

It may need moved down a notch

Apparently 05+ has a non adjustable needle. I did put a washer under it to richer it up, I did not notice any difference.

[JOHNDOE83]

Originally posted by qc dsm tsi
Back on topic please.

in the links I posted there is detailed instructions on how to tune your jetts.

For the main jet you have to start large like 200 instead of 170-175. You go large on jet sizes until the topend stutters instead of fully revving out, then you go back down in incriments of 5 until it fully revs out.

You simply cannot just throw a 170 in and say its jetted.

The 42 pilot is what you need, not the 40. Turn your a/f screw out to 3 turns and see if there is improvement in the low end.

The motor will only be to rich when it stutters and doesnt fully rev out.

If you wanna check the plug you HAVE TO use a brand new plug, from a dead stop go to max RPM in 4th or 5th gear, then pull the clutch and kill the motor while coasting to a stop.

You then have to cut the threads off the plug and check for the carbon ring inside the plug, you CANNOT just pull it out and say the color looks good.

If there is no popping or backfiring on decel your pilot jet is fine and almost perfect.

If there is no hesitation or bog or stumble in the middle of the rpm you needle is fine if not perfect.

The main jet can only be tuned with the above mentioned procedures, in many cases even a stock bore 400ex needs a 180 main jet.

[qc dsm tsi]

Originally posted by JOHNDOE83
in the links I posted there is detailed instructions on how to tune your jetts.

For the main jet you have to start large like 200 instead of 170-175. You go large on jet sizes until the topend stutters instead of fully revving out, then you go back down in incriments of 5 until it fully revs out.

You simply cannot just throw a 170 in and say its jetted.

The 42 pilot is what you need, not the 40. Turn your a/f screw out to 3 turns and see if there is improvement in the low end.

The motor will only be to rich when it stutters and doesnt fully rev out.

If you wanna check the plug you HAVE TO use a brand new plug, from a dead stop go to max RPM in 4th or 5th gear, then pull the clutch and kill the motor while coasting to a stop.

You then have to cut the threads off the plug and check for the carbon ring inside the plug, you CANNOT just pull it out and say the color looks good.

If there is no popping or backfiring on decel your pilot jet is fine and almost perfect.

If there is no hesitation or bog or stumble in the middle of the rpm you needle is fine if not perfect.

The main jet can only be tuned with the above mentioned procedures, in many cases even a stock bore 400ex needs a 180 main jet.

Thank you, this is good information. My "back on topic please" was directed at the argument above...

[JOHNDOE83]

We werent arguing, we were just discussing Obama's healthcare plan:chinese:

In our discussion we seemed to have left out the jetting details, when I read the "back on topic" I noticed we didnt really answer anything. :rolleyes: