Hey i heard on here somewhere that taking off the airbox lid took away power because the carb needed the airbox lid to work properly..well is this true for making good hp you should have it on because i just thought ide take it off for a lil rip the other day and wow it seems to pull like CRAZY through all the gears but it seems to die off at high rpms??? or maybe it just seemed to have all this low end power because of the monster noise it makes when its off?

 

I have been told this before, but cannot remember exactly what it is. The stock carb needs vaccuum pressure for the slide to operate properly, and when the airbox lid is removed, this vaccuum is lost. I'm sure someone here will chime in with a little more detail.

 

The stock carb does need the vacume to open the slide. On a dyno mr hp said it made more power with it on, in my experience you can manipulate the slide by cutting the coils to allow for less vacum and gain the extra response by not running your air box lid. I take them off every bike I tune. Good luck! Jed

 

When I bought my trinity setup, they gave me a 190 main, and required airbox lid removed. Right in around there, I had cut some coils as well, so I have not noticed any loss of power. I have been meaning to jet down a bit and reinstall the lid and see where I stand, but haven't gotten around to it. If I do have more grunt in there hiding, I wouldn't guess it, she pulls hard enough as it is.

 

The carb does work on a vacuum, but the statement that it needs to lid to work correctly is INCORRECT! I dyno tested a couple of DS's and without the lid the quad gains about 1 second quicker acceleration time in 4th gear compared to running it with the lid in place.

It does not increase HP by much but the acceleration times do not lie.

If you don't understand how to fix a carb to make it work better without the lid, you might get the impression that the lid gives more power. Get the combo right without the lid and it will make more HP than the lid on place.

Adding the lid to fix a carb problem is like doing things backwards.

The motor needs air to make power. Restricting it is not the best way to make more power. Fix the carb problem at the carb and don't try and fix it by restricting air intake.

 

getting it right without the lid might be hard for most.

 

No its not. The guys DS650 that showed the gain in acceleration was using a K&N air filter, Dynojet kit, running dynojet recommendations and a modified slider and cut spring.

Can I shed some light why I think these problem of misunderstanding and misinformation come from.

People have limited dyno time. They also pay for this time and therefore have to rush to try and test things.

Now this is the normal process of testing. Take a stocker and get the dyno output. Remove the lid. The result, damn, it is worse, hence it must be a bad thing. So, the lid goes back on and the try and test the next mod. Remember time is limited and its money out of your pocket! To test the slider action and try and find a fix for the slider mismatch might takes hours of dyno time. You will have to try lots of different springs, needles and vacuum hole shapes and sizes. In the process you might also write off some slider which just adds to more money down the drain. Hence people taking shortcuts and making assumptions that might not be correct. If you try something you need to take it to the end before you can comment if this will work or not. If you don’t have the time or the right needle or slider spring to work with, the lid in place, might very well give you more HP. Remember that the slider and spring was designed to work with the lid in place. When you remove the lid you need to change the way the slider moves and the needle to match it. Cutting the spring might not do the trick. You might have to increase the vacuum inside the slider. To do this you need to play with the holes in the slider.

If you think about it. With the lid in place, there is a partial vacuum inside the airbox. The intakes to the airbox do not supply enough airflow for the motor. Removing the lid will solve this partial vacuum and there WILL be more airflow. If you loose HP with more airflow, you are NOT addressing the problem inside the carb. More airflow and the right fuel mixture MUST give you more power. It’s that simple.

I will test this setup early next year to make sure what the best combo is and give feedback.

 

Thanks Freez, you said whats on my mind but saved me from typing it out. Simple truths, engines are air pumps, the more you get in it, the more you get out of it. Jed

 

I removed the whole air box and use only the tube to an K&N It runs like a striped a$$ zibra and thats no lie so vacuum Naahhh your fine removing it. What lid?

 

JMO all my dyno time is seat of the pants like 90% of the guys here. I have posted this B4 but Im here to help. I jetted and rejetted and came up w/ the same results. It still ran like a raped ape w/ or w/ out the lid. but in a drag race I lost every time against a similar set up Ds w/ my lid off his on. but a heads up on drilling your slide, do some research ask some that have done it. JM2C "Seat of the pants "

if you ride w/ some one that your neck n- neck in a race, try w/ on and off, jetting to your best.

Sam