Cammer,

Did you do all my recommended mods - spring, slide and disconnect balance tube?

My mods are with the airbox lid on. If you must run with the lid off, then raise the needle to
6th groove from top(richest position).
Do a test run for power and pull plug.
If better and plug is still white, then start to use a larger main (DJ190), etc, till plug has light tan ring on top of porcelain.

 

OMR,
Thanx, I will give it a try. I was going to just change the main jet to 190 because it was only popping above 6,000rpms during acceleration. Every where else it seem to have more power than the stock needle.

 

OMR,

Here's what I have tried so far. My goal is to achieve 80+ mph with the quad studded up for ice racing.

1. Modified the stock end cap with a 1.5" opening, spark arrestor still in place. K&N airfilter. Changed jetting from 165 mikuni to 175 mikuni, moved needle to richest position. Removed air box cover. I gained a ton of bottom end and midrange, enough to gear up to 17/38 with 20" tires. Ambient temperature 60 F (also ran this jetting in 70-75 F without troubles), elevation of 1840' above sea level. Quad ran rich if airbox cover was put back on, bogged in the midrange.

2. Changed the end cap outlet to 2" opening and removed the spark arrestor. With no jetting changes, quad lost acceleration, obviously lean. Put airbox cover back on, quad gained acceleration, but still lean.

3. Checked the carb spring. Looks to be stock, length approximately 3 1/8". Put back in.

I have ordered a DJ jetting kit to try the rest of your modifications, but it still has not arrived. Therefore, I will try your slide mods, starting with drilling out the stock holes to 1/8" and remove the balance tube. I will keep the airbox lid on and cut down the stock snorkels to your recommendations. From other posts, the slide should fully open and therefore richen the jetting. My next step will be to install the DJ needle and rejet the main accordingly.

Sorry if I missed this somewhere, but do your recommended slide mods work both with or without the airbox lid? I still can't get my head around how you can create more power with the lid on and your snorkel mods. Are you trying to develop a ram air system, and is this what allows the slide to open fully? I do not fully understand a cv carb, used to dirt bikes with the slide attached to the cable. I can see why you would want to have the slide open fully, but if all things being equal, with the slide fully open, the engine should recieve more air with the airbox lid off, allowing you to richen the jetting, creating more power. But if the slide will not open fully with the lid off, then I can see how you can lean out the jetting and get more power. I'm willing to try all of your mods to a tee as soon as my jet kit gets here, but will the mods to the slide force me to keep the airbox lid on? I guess it's only a $50.00 part to replace.

 

So I snuck home from work to try a couple of things. I closed the airbox and the thing ran like crap. I took the airbox lid and air filter off (just rained, no dust ) and she goes like snot. I am to assume it is rich and should downsize a jet?
OMR Will you mods work on an open airbox? I need more air based on my little experiment.
BTW I have only cut the spring when I put the end cap on as per MRHP.

 

i have a ds with a w/b e-series exhaust and a uni air filter and i put 22 inch tires on instead of the stock 20's and i dont want to change the gearing i want to keep it the same but gain my low end back do you have any suggestions on what i should do to the carb/airbox should i run with lid on or off? only thing is last time i tried to run with lid off it seemed to cut out

thanks matt

 

ds650iceracer,
When I started this project my goal was to run with the lid off. So the 4 1/8 vacuum ports were originally with lid off. I still recommend this size with lid on.
I thought I had everything figured out, but at this time I have gotten my best results with lid on.
With lid off there is definitely more power at bottom and mid, but upper mid and top just stops pulling.
The only people that seem to have good luck with the lid off, are people who are above 4000 feet elevation. Atmospheric pressure at that elevation causes the cv carb to respond differently.
I haven't given up on trying to run with the air lid off, I just got to get back to testing.
CV Carbs love velocity, inertia, no turbulance and controlled reversion. When all four are working together you get an added benefit called resonance. What you referred to as a ram effect.
With the lid off, at low end you have lots of air volume and thus motor hits really hard.
But as rpm's increase the air starts to tumble going into the airbox and inertia is out of control.
By upper mid and top there is uncontrolled reversion and velocity cannot keep up with motor requirements. Motor revs but not pulling.
I know what the problem is, but how to design a feature into the airbox to control air turbulence,
has got me temporarily on hold. My son has been very patience with me and my experiments.

If you do the Carb Mods as stated, you will be very close. In winter you will need to be in the 3rd groove and jet main to 195. This with DJ needle and jets.

 

Cammer,

Lets again do a review.
First, as I previously asked, did you do the slide mods and balance tube?
Second, what is the length of your spring?
Third, are you going to run with the lid on or off?

If we work with all the facts, I can help you better.

Lets get your quad kicking.

 

05dsrider,

Do the Carb Mods as stated. Lid On
It will add power bottom to top.

If you do not change the gearing, I highly recommend you buy the Big Gun CDI.
The more aggressive ignition curve will add more mid range torque.

Do Carb Mods first, and after riding decide on gearing or cdi.
If you are not a drag racer, Carb Mods will be enough.

 

Thanks OMR. I'll still waiting for my jet kit. I'll post how I make out after I make the changes.

 

Just to throw another wrench into the works, I believe there are 3 or carb springs varying by part #s and spring tension. I don't know if the lengths vary.