This is what I found, after some extensive testing.

If you run other cams, high compression pistons, and so on, you need to run with the lid on. Reason I say this is because the stock carb is not able to flow enough fuel to compensate for the additional airflow.

The stock carb is your limiting factor, and it seems that the stock carb is just not capable of flowing enough fuel to supply a main jet larger than a 195/200 DJ jet.

So, as much as I hate this, to limit air intake, so that the stock carb can keep up with the fuel delivery, you need to run with the lid on.

I don’t know if OMR's emulsion tube he is working on will address this problem, but if you are looking for more power, my only advice at this stage is to upgrade to a bigger carb, that can flow more fuel.

 

Freez,

Because your atmospheric pressure is at 12.5 for 4500 ft elevation.
I would like to make a few recommendations:
1- Drill the front 2(two facing the intake tube) vacuum ports to .140(2 rear still at .125).
2- You need to increase vacuum signal by either running lower octane fuel or ignition with more timing. I have run 87 octane with 30 degree's of timing with no problems.
The Big Gun cdi has 28 degree's. Stock is 26.

By increasing vacuum signal, by increase timing and lower octane, you will gain both bottom and top performance.

Do the ports and lower octane gas first, lid-on and lid-off.
Let us know how the power curve has changed.

OMR

 

OMR, I assume the two vacuum ports you are talking about is the two stock holes in the slide?

Then, I tried running the stock CDI and I also tested an aftermarket CDI (SRP unit). With the aftermarket CDI you don't notice any gains on the dyno, yet people who ride the bike before and after the new CDI was fitted say they feel the difference.

The bike as it is now, is running the SRP CDI.

I am not sure how the additional vacuum is going to aid me in getting more fuel into the motor. Yes, it will suck more, but I still believe there is a fuel restriction flow problem in the stock carb. I tried the size 200 main and the 210, and the air fuel ratio is exactly the same.

I cannot get the A/F ratio lower than 14:1 with any size main jet I tried.

 

Freez...can I get my quad back one day??? kidding really appreciate the time & effort going into it

 

Freez,

The two vaccum ports I am asking you to enlarge are the two new extra ports I recommend adding per the Stock Carb Mods. When done there should of been four(4) vacuum ports.
The stock two are towards the motor and can only be enlarged to .125(lack of space to go larger). The extra two are drilled towards the intake boot. There is more room there to go larger if necessary. If you did not drill the extra two ports, then start at .125 .

What grade of fuel are you running? When we ride in high elevation we run 85 octane.

OMR

 

The slide has 4 ports in it at the moment. Then, we are running 93 to 95 Octane, as we don’t get 83 here. Only 93 or 95.

I don't understand how the 85 Octane will enrich the fuel mixture. The mixture is up fine until the last 1/3 of the RPM range. From there on, it goes a bit leaner to what I personally like to run. This is typical main jet fuel delivery range.

Let me give you an overview of the A/F ratio.

I start all my dyno runs in 4th gear from 2000 RPM onwards. At 2000 RPM, I give it full throttle and let the bike run thru the RPM range. The Air fuel ratio goes rich, around 12 or 11.5:1 for about 1000 RPM, then it goes towards the 13:1 mark at about mid RPM, and then it goes leaner towards 14:1 from there on, all the way to RPM limit.

If I open the slide any faster at low RPM, it will dump even more fuel thru the carb and make it run even richer towards the 10:1 A/F ratio, and it might very likel choke the motor. I need to get more fuel out of the carb towards the higher RPM ranges, and the slide or needle, has very little to do with the fuel delivery at high RPM.

 

Here's a new chapter on the stock carb mods story, I had a spare stock carb and started tinkering with it. I haven't had a riding trip to test the results but I noticed quite a difference on the back yard drag strip.
First, I ported the air filter side of the carb. I have stock and modified pics posted on my page.

A. These are castings are around air bleeds on both sides. I removed metal down to the jets and basically formed it around them into the shape of a hollow point bullet.
B. This is a cast in bump to provide material where the body was drilled for a passageway. I smoothed it but left some as to not go into the passageway.
C. The Biggy. These two passageways with a siamesed casting are useless and are plugged with brass. I removed the casting completely and thought of covering the rest with epoxy but figured I'd improved this area 90-95%. This thing forms a tear drop shaped area of disturbed air around it and is directly in front of the main jet well. It couldn't hurt to remove it.
I also knife edged the throttle plate and smoothed out the throttle shaft.

Progress report-I thought I'd really screwed up, probably the "well" that was around the air bleeds but found my choke stuck on. OOPS!
I did alittle rejetting and upped the main to a 185 Mikuni and Dynojet needle third notch down. The back yard dyno said it was running good or at least as good as before the mods.
I messed with needle positions and found that I could use a small spare washer for a shim to move 1/2 needle notch positions! Things were getting more responsive.
I've always felt that the Dynojet lacked something on the top end. I've swapped back and forth with the stock needle and the Dynojet can always be dailed in for more low and midrange snap. I believe Oldmanracing and Mrhp have stated the stock needle comes out on top on a dyno. I had a spare Dynojet needle and ground the tip down by chucking it into the dremel and spinning it on some sandpaper. I tried to copy the last 1/4 inch taper of the stock needle, which has a sharper point. I also noticed the stockers tip is flatter so I copied that as well. I did this by eye but I've got a good eye for this. I used light pressure and it didn't take much off at a time.
Now I was really getting somewhere, The quad felt like it had a very steady gain in power and my back yard seemed smaller.
I decided to try OMR's recommendation on drilling my slide, I'd always thought my throttle response was snappy but WOW, now I really need to watch the throttle in the back yard, or I'll end up over backwards.

I just thought I'd post this to let others know that stock carbs still have a little extra to be had. The dremel porting could be done in about 2 hrs and back to running.
I'll post an update after my next trip to the dunes and let you know what kind of results I see.

 

To OMR.
Maybe you can post an informative post about the TM42/45 I am still having diffuculty getting my jetting right, and I have tried all the recomended setting's/jets.

 

Hey guys, I am new to this board and got caught up in this awesome thread. So after reading the whole thing. Without hesitation off came my carb.
I just can't help my self. Now I have some questions for the Gurus of the DS .
So far this is what I have. 01 DS650, K&N cut air box lid with a outerwear filter, Trinity stage 4 full system. and every thing else is stock.
OK so I drilled my holes in the slide , Measured my spring and it came out 3 1/8 with 27 coils. Out of a 01 ? Put the filter on my breather tube outlet on the carb(pix).
And will be installing some smooth air hoses. setting my float level to OMR specks. and have already ordered the Dynojet kit.

Ok. I ride mostly at Glamis Ca which is at sea level. What would be a good starting setting with jets main (.165 in now) and (.45 in now)slow,
needle clip position, air screw adj. and what ever else I might need to do.
My thoughts at a stating point was going to be Main .190 slow .45, 3rd clip from the top and 4 turns out?

Do you think that is a good start? If not what would be? I am trying to go off of what I read here but it is a lot to absorb.
Thank you for your help and the valuable information you provide.
(I will have pixs of my progress in my profile)

 

With modified lid you will need more fuel at bottom/mid.

Raise needle to the 5th groove from top. After installing into slide, wiggle needle up and down to be sure that the needle is not hitting the plug retainer. If no movement, grind needle head down to first groove.

Pilot screw should be turned out 5 turns with lid open.


I have been doing some testing with lid off and will be posting an update soon.
Finally figured out how to control fuel at top end.

OMR