I just changed the main jet in my DS from a 180 to a 175 because the plugs were still black, the clip is in the second position and I ride at 5500 ft. After I put in the 175 and changed the air/fuel screw to 2 I started it up and black exhuast was coming out. I let it run for awhile and now it's just doing it when I rev the engine a little, what could have caused this my elevation here is about 2000 ft. Any help would be greatly appreciated!

 

What modifications do you have? Pipe? K&N? Is your air box lid on or off?

Are you running Mikuni or Dyno Jets?

Try dropping your needle a notch and leave the jet where it is.

What year is your quad? How many hours do you have on it?

If you have been running like this for a while, your spark arrestor screen may be sooted up which compunds the problem.

Sooting means you are running rich. Look at Buttfungus' web site to get an idea of what others have set-up for their quads based on the same modifications (i.e. pipe, filter, etc.)

I think I run a 170 or 175 Dynojet when I am at Sand Mt. (4000 ft.) and I have a Pro-Circuit pipe and K&N filter with OuterWare. Buttfungus also has the Mikuni to Dynojet cross ref. chart and instructions for installation of the dynojet. I think my needle is on the third clip (whatever the Dynojet instructions say.)

Your idle adjustment is just for the first 25% (approx.) of throttle so if you are sooting when you rev a bit it is a needle / jet adjustment that needs to be made. Once past 1/4 throttle the adjustment screw isn't doing a thing for your tuning.

 

I have a 2000 DS with a white bros. pipe, K&N filter, lid removed, and I have the needle and jet exactly as Dynojet says. What do I do if it is "sooting" I've got over 40 hours on it.

 

reignman78,

did you plug your snorkle holes since you removed the lid? I had a problem with mine running rich after doing that because my seat was vaccuming to the airbox opening...just a thought. Try running without your seat and see if your exhaust cleans up...

jim

 

Try the needle at the 3rd notch.

If still sooting, check your spark arrestor screen to be sure it isn't sooted up (not sure how the White Bros. is built.)

 

jiminok, if I were to remove the snorkels what do I do with the tubing that is inserted in the left snorkel, and what did you use to plug them?

 

The WB pipe is disked, no screen.
With the lid off, you should follow the stage 3 instructions, rather than stage 1. Only thing is that this will get you even richer. Purhaps there is a problem, like a stuck choke or float bowl needle valve, or mal-adjusted float level. If the bike runs great, just a little rich, then its probably not the choke valve sticking. A stuck or mal-adjusted needle valve/float height can cuse a rich situation. There's always the slim possibility that you are burning some oil too, either from bad rings or valve seals. Not trying to scare, just covering some more possibilities....

If you remove the snorkels, the tube you're asking about is the crankcase breather and should have a filter installed on the end of it. You can get a little pleated filter with the same inside diameter and stick it on with a barb.

 

Just a quick doube check, if you rotate the air/fuel mix screw clockwise you are richining it and counterclockwise you are leaning it? by this I mean it as if you were laying on the floor looking streight at it.

 

idle mixture screw - clockwise to richen (towards the seat), counterclockwise to lean (away from the seat).
This effects fuel/air mixture at idle. Pilot jet takes over from there to 1/4 throttle, needle from 1/4 to 3/4, main at full throttle.

 

Along the lines of what Hightower is saying, Stage Three Instructions for Dynojet call for the needle on groove #3 from the top, using all stock spacers. It also calls for a 180 main jet from 3000 to 6000 feet elevation. Mixture screw 2 1/4 turns out.

I left my snorkel tubes in place and have not noticed any issues.

You can simulate a little altitude by putting your air box lid on your quad when you are at home and taking it off when you go up in altitude to ride. This may make it easier to adjust the jetting once you get to your riding area.
Let us know how it turns out.