When you run with the lid off,
is it better to remove the snorkel tubes and plug box;
or leave tubes attached and open?

My gut says that there may be too much air turbulence!

 

ide plug them

 

Depending on what carb/pipe your running. I know mine ran optimum with the air box lid on with the 2 vent tubes removed. Of course, I was running the stock carb/drag pipe combination.

 

This is with the stock carb. I have gone a different road.
Balance tube disconnected with filter.
Modified spring.
Modified slider.
Modifed emulsion tube.
Different needle.
The carb does not need the negative pressure of the airbox to open.
And when I say open, I do not mean at high rpm's only.

Now I have to learn how to get more air - good none tubulant air.

 

Guys, please note that the CV carb on the DS, DOES NOT, require a vacuum in the airbox to open the slider. I have no idea where people get this stupid idea from. The vacuum to open the slider is generated by air flowing underneath the slider. The air flowing past the holes in the slider causes the vacuum to suck the slider up and open the carb, not the vacuum in the carb breather hose.

Now, please take a look at where this "vacuum hose" as some people call it connects to. It connects to a opening underneath the slider diagram. The vacuum to open the slider is at the top of the diaphragm and the passage underneath it is actually a breather passage, to let the diaphragm “breathe”.

Now do yourself another favour and blow into the pipe. What happens? The diaphragm moves up! It opens the carb when you blow on this pipe. Now suck on that pipe and see what happens… yes.. it stays closed! So, now ask yourself how is it possible to do this when those other guys are telling you it needs a vacuum to open the carb, when air pressure opens it, NOT a vacuum? THEY ARE WRONG and have been feeding you the wrong info for ages. Like I said, you need the vacuum ON TOP of the diagram and by blowing on the breather passage, you are pressurising the bottom part of the diaphragm and pushing the slider up. If a vacuum was here, it will suck the slider down or keep in closed.

Now, here is a little tip to open the slider a bit quicker. Some people cut the spring. Yes that works, but the spring tension is critical to keep the slider stable at lower RPM. Cutting the spring might mess the slider stability up and cause it to flutter. There is a better way of opening the slider quicker without changing the spring tension. The breather pipe from the carb connects to the intake tube between the carb and airbox. With an air cleaner installed, the pressure in the intake tube will cause a vacuum between the air cleaner and the cylinder. This vacuum is then fed to the breather pipe, then to the carb breather passage, where it competes with the vacuum on top of the slider diaphragm. The two vacuums are competing with each other, causing the slider to open slower and smaller. Now, remove the breather pipe, block the hole in the intake tube with a plug and install a small K&N breather filter on the carb breather pipe. Now you will not have a vacuum underneath the slider and free flowing air can move in there when the slider moves up. This means a smaller vacuum is needed to open the slider and it helps it to move quicker and open larger with less vacuum.

I have tested this on DS's, raptors and other bikes and they all show better throttle response and quicker/larger carb openings, causing better power at low to medium RPM range. The dyno shows this time after time.

One last little point. The predator 500 uses the exact same carb as the DS650. Polaris has this little air cleaner on the breather pipe as standard on the bike. So, it is not just me that uses this trick, Polaris also understands how this carb actually works.

So guys do yourself a favour, loose the damn lid and let the motor breath, do this little breather mod and stop messing about with cut springs and trying to tie down the intake tube to prevent it from being sucked closed. If the airbox is flowing correctly, it will not suck that intake pipe closed. The pipe being sucked closed is a sign of poor airflow and a massive vacuum on the intake system. The bigger the vacuum on the intake the less power you will have. This is so easy, yet some peopel don't see the light.

The more you close the airbox, to try and fix the carb opening, as some recommend you do, the less air will flow to the motor and the less power it will make.

Understand how the carb really works and then you will be able to make that DS breath properly. Jet it correctly and you will get the power. It is that simple.

Then I would leave those holes open, or even better yet, loose the whole box and run with an open filter if you can.

The problem with the stock airbox is that the seat closes a big part of the intake to the airbox. When you sit on it, it even closes it further. Closing the intake holes will leave you with a small opening between the seat and airbox, plus, the airflow will be one directional. This means that the bottom part of the filter will not flow the same amount of air as the top part of the filter. The more holes you can make around the air filter, the less the air needs to flow around to get access to the whole surface area of the filter.

Turbulence at the speed quads run, is minimal, so don't let the bother you much. Give it lots of air!

 

I agree, RWR has been selling carb mount air filters and little breathers for the carb breather tube since day one, many people have ran lidless or carb mount filters on these carbs for many years. over the past year there has been much controversy come up to challenge this, but your explanation is pretty simple and to the point.

the seat is very close to the airbox opening, even after also removing the gasket around the top. the holes in the front of the airbox need to remain open even after removing the lid. to keep splashes out 90 degree PVC elbows from the hardware store are ideal. i run lidless and 90 degree elbows in the front holes, and hit creek crossing ***** to the wall with no water getting in. leave the drain cap off so any small amount that may come in can run right out.

no matter what carb you run, cv or flatslide, airbox or no airbox at all, the old model intake boots will collapse at high rpm, I can see it when I rev with the seat off, there must just be enough resistance on even a clean K&N to allow enough vacuum inside the boot for this to happen. but the new model boots are much more rigid and do not. I ditched my old '01 model boot for the new and the collapsing is gone. when I say collapsing, it is very minimal, and only at rpm's beyond my peek HP producing rpm, so it is not much of a performance robber since I should be in another gear by the time it occurs anyway, but some circumstances get you into situations of overeving for one reason or another sometimes, and its nice to just have the issue gone for a mere $20 spent on the upgraded boot.

 

No lid here, pulled the snorkles and capped the holes. Amen guys to the hole"leave the lid on", it needs the vacuum

 

w1ngnut, please explain to us what you mean? Do you like the lid off or on. Do you agree that you need a vacuume or not, to open the slider?

 

Hightower/Freez,

Over the last 1 1/2 years we have shared a few discussions on the stock carb mods.
I think the direct mount filter proved to us all that with more air came more power.
It is just too tight of an area, I raised the seat and for long rides it was not comfortable.

The clear vacuum or balance tube did have its place.
As a stock machine, lid on and different exhaust,
it was a balance tube to controll bottom flutter.
The old spring cut 4 coils is identical to the new 05 spring.
3 1/8 " long and when installed, an at rest pressure of 35 grams.
This very low pressure gave good throttle response,
but with the spring being very aggressive, the slider bounced back easily.
The balance tube did a good job.

The moment you take the lid off the balance tube becomes useless.
Like Freez says, it now hurts performance. Plug the fitting going into the
airbox and add a filter to the clear tube.

The slider is modified per Freez's recommendations.

The spring I am using is 100% stiffer at rest and only 50% load of stock when open.
Throttle response is too agressive for the stock needle to add the needed fuel at bottom.
The needle I am using gets .011 thinner than stock and then returns to stock size at end.

I have great throttle response, good needle, but now I need more fuel.
The stock emulsion tube can't keep up. I have a new emulsion tube with more holes.

I just installed a new Big Gun CDI.
Wednesday, my son and I did some testing.
After a year of trial and error, it finally has come together.
The grin on my sons face tells it all.

We will tests more over Labor Day holiday.
In Wisconsin we cannot remove the airbox to run in stock class.
So I will remove the snorkels to add more air to lower part of filter.

Thanks for always good advice.

 

I would like to know if the slider mods we talked about help in any way? Could you notice any thing before and after the slider mods?

Did you have the needle specially made or was it one you got over the counter.

I know you did some special work in the emulation tube. You still need to enlighten us on that peace of work.