What jetting for removing the airbox lid???

[ryder_trig]

I've read all the other threads but couldn't find exactly what I was looking for. What jetting should I use for removing the air box lid on a completely stock '04 400ex?? My wife is the original owner and no one else has touched the quad so I know that the stock jetting is still in place.

[rcatvrider]

With a stock filter it doesn't do all that much. Maybe go up one size on the main and possibly one on the pilot if you find it to be running lean.

[ryder_trig]

I plan on using a K&N filter along with the sparks 6 degree advance timing key.

With a K&N and open airbox lid try a 150 or 152 main.

[ryder_trig]

foxhondarider, did grinding down the exhaust welds and removing the choke show any noticeable gains? What about the sparks ignition upgrade, did that increase all the power that it claims to?

Originally posted by ryder_trig
foxhondarider, did grinding down the exhaust welds and removing the choke show any noticeable gains? What about the sparks ignition upgrade, did that increase all the power that it claims to?

The choke removed was felt, the timing key was really felt but grinding down the exhaust header welds was not felt but my welds werent bad. There was hardly anything to grind down almost like it was done before but that goes to show how different each quad is. If anything Grinding down those welds gave .1HP if your lucky but I like the thought knowing i've done everything possbile thats free to get power from it. My quad will pull away so hard from my brothers and he is getting more traction cause he has Razrs. 1st or 2nd were even him with more traction will usually pull a half length. As soon as we hit 3rd gear I rip past him like its nothing then 4th oh man he's gone. I assume my quad running that much stronger is just a combination of everything. Every bit counts. If its free why not do it? I rather do everything possible thats free to gain even the slightest power just to know I have done everything possbile to get the most out of the motor. I would like to try carb porting and a port and polish more of a casting cleanup in the head but thats why there are professionals I would hate to screw up the head even though theres another complete 400ex motor chillin in the garage

[ryder_trig]

Awsome feedback. I think I'll start with the sparks and the k&n with prefilter and the lid removed. I'll try a 150 on the main jet and see where it puts me.
Another thing I noticed is that when I start it with the air box lid off (keep in mind it's bone stock) it back fires through the carb at idle. Should I go up one size on the pilot?

[rcatvrider]

Originally posted by ryder_trig
Awsome feedback. I think I'll start with the sparks and the k&n with prefilter and the lid removed. I'll try a 150 on the main jet and see where it puts me.
Another thing I noticed is that when I start it with the air box lid off (keep in mind it's bone stock) it back fires through the carb at idle. Should I go up one size on the pilot?
A 150 main will be too lean. The smallest main I have seen with those upgrades is a 152 main but I'm guessing it will be 155-158. With those mods you can also go up one or two sizes on the pilot jet.

[soyo]

i have a 45 pilot and 170 main with lid off, k&n, and slip on. around 800 feet if this helps