Guys, listen here please.

The air screw adjustment only effect idle to 1/4 open throttle. The needle clip position effect power between 1/4 and 3/4 throttle, and the main jet effect 1/2 to full throttle.

Turning the air screw is going to help jack for anything above 1/4 throttle, so leave that alone. If your quad starts and idles fine, then your air screw is good to go.

The needle position effects 1/4 to 3/4 throttle, so if you have a lag or a flat spot in mid range then mess with the needle position. Now, if you have problems under full throttle or heavy load it can only be the main jet.

Do the test with or without the lid. See if it helps with the problem or making it worse. It sounds like the bike is running a bit rich, but removing the lid and causing the bike to run better will prove that. If the problem gets worse with the lid off, then it indicates you are running to lean and the main jet must go up.

Leave the needle and the air screw alone. Stop messing with things that is not causing the problem.

Like I said, the DS's here are running 185 DJ mains, needle in Dynojets recommended clip position and its summer here with an altitude of 5000 ft. All of them have been set on the dyno and with a air to fuel ratio meter, so I know I am right here. These DS here have slip-on or full pipes, they all run similar jets.

If you run it in winter at 600 ft there is no way that main jet of 180 is going to be to large.

 

Freez is right on the money about the jetting. Over here in australia im at sea level and my ds has an endcap only and k+n filter, dynojet 185 main, dynojet needle 4th clip from top, no lid or lid rubber and runs perfect. !!!!!!!!

 

When i did mine it started fine,ihad to feather the gas to higher rpms.Top end it bogged.
So i changed jet and needle one at a time,until i didnt have that.Then i checked my plugs
they were still wet and black.I checked the screw,I have never touched it and it was 5.5 to 6
turns out.I set it at 3 out ,NO more probs and it runs good at 35 degrees.This is with and endcap
mod.

 

Camds650
Freez


Freez[img]i/expressions/face-icon-small-confused.gif[/img][img]i/expressions/face-icon-small-confused.gif[/img][img]i/expressions/face-icon-small-confused.gif[/img][img]i/expressions/face-icon-small-confused.gif[/img][img]i/expressions/face-icon-small-confused.gif[/img][img]i/expressions/face-icon-small-confused.gif[/img]

 

When you coming out of a corner or you are under load (running up a hill and accelerating) your usually have the throttle pinned open. Very few people will have 1/2 throttle riding around corners and going up a hill... what fun is that. This is main jet area, not needle. The fact that he says he can open the throttle slowly and there will not be a problem. This seems to indicate that the needle is fine, since he is only getting the wrong mixture when the throttle is slammed open. Slammed open with problems is main jet, Slow easy open with problems is needle.

Like I said. Between 1/2 and full throttle the main jet plays a part. The needle also play a big part in the 1/4 to 3/4 open throttle range. So, between 1/2 and ¾ throttle both the main jet and the needle produce the right mixture. The two work hand in hand. The problem with main jets is that the 3/4 to max throttle position you cannot feel the loss or gain in power that much. So if it is to rich, the bike is near full RPM and most people cannot tell if you loose a HP here or there. The lower RPM ranges loss of power is more noticeable.

Then, on top of that. I have installed lots and lots of dynojet kits on DS's, Raptors, TLZ400's YFZ450's and 400EX's and not a single one I had to mess with the needle positions. I used what Dynojet recommends. It works period. The trick is to get the main jet right 1st.

Hell dynojet spends lots of hours getting that thing right. My dyno and air:fuel ratio meter agrees with them.

The best way to jet is as follows. 1st get the bike to idle right and run well till 1/4 throttle. This is done with air screw and pilot jets.

You can actually remove the main jet and needle and the bike will start, idle and run with low throttle opening.

Next thing you need to set the main jet right. This can only be done with top end speed runs. It is not that easy without a air:fuel meter. What most people do is keep adding bigger and bigger mains till the quad starts stuttering. Then go back a jet size or two. Once you have the quad set up perfect to run as fast as it can go, the main jet is good to go. The last thing is trying to change the needle, to get the midrange right.

Messing around with the needle you might fix the mid range, but the top end is going to be messed up with the wrong main, costing top speed and bad performance at low RPM with big throttle openings.

 

I hate to disagree Freez, but I had the same mods at one time and the dynojet needle was the problem. I tried every jet they had and nothing worked as well as the 180 which is a hair bigger than the 165 mikuni and the stock needle in the second to the richest setting. Mr. Horsepower helped me with the jetting. The dynojet needle is tapered to much and affects the mixture from 1/4 throttle to full throttle. I don't think enough DS's are out there buying their kits, cause their recommended set up is wrong.

justin

 

I have 4 DS running the Dynojet kits. It works great on all of them. The mixture is near perfect all the way from low to max RPM. One thing that might cause problems is the altitude or the end cap. Like I said I am at 5000 ft here, and have never tested the quad at sea level. The guys with these settings are running either full or slip-ons. These quads have been down to the coast and the guys did not come back and told me it run badly, which will lead me to believe that it will work fine for sea level.

Maybe the end cap is not right for the dynojet needle.

The rest I have tested. Slip-on with lid and without, same for full exhaust systems. Even stock DS, with no mods run fine with the dynojet kit.

I will be testing a end cap on the dyno soon, I might agree with you guys in less than a month.

 

No way if perfect at 5000 ft it ran well at sea level. When I bought the DS I though "HIP HIP HORRAY!!!" a four stroke, I will never have to worry about jetting again. WRONG. If you go more than 3000 ft difference under optimal circumstances you better be moving the needle. (normally 1500-2000ft) You might not notice as much going down as going up in elevation but there will definitely be a power loss. (significant enough that any dude with a good friend who dynos their bikes several hours a week would notice it) Maybee they don't want to argue with you so they didn't say anything.lol

justin

 

my experiance in jetting is more along the lines of crackers, at sea level my bike dynoed at 15% more power than @ 5000 feet where I live. It wheeled way easy, just crack the throttle and up it went, I'm envious of the guys that ride at sea level. You'd be surprised at what a difference 5000 feet will make.

 

Did someone say K&N Power-up Pack with Dynojet Neddle and Jets? [img]i/expressions/face-icon-small-happy.gif[/img] [img]i/expressions/face-icon-small-wink.gif[/img] [img]i/expressions/face-icon-small-blush.gif[/img]