Proper Jetting

[Pack]

A friend of mine has an '04 DVX400 with a FMF slip-on exhaust, with a stock air filter. We live in Missouri, with around 1300 ft above sea level.

From what I've read, he needs to go to a 25 pilot, around 145 main, and I'm not sure on how to adjust the fuel screw.

What do you guys suggest?

[cataway]

i would call thet jetting right .
do you know were the screw is ? can you get to it to turn it ?

[Pack]

I have no idea where the screw is, or even how many turns out it should be to compensate for the pipe.

Is the "air screw" the same as the fuel screw?

[cataway]

air screw ??, no this is a 4 cycle http://i44.photobucket.com/albums/f9/cataway/Carb_Labeled.jpg

the screw your looking for is under a brass soft plug that has to be removed to get to it, that is if no body has ever adjusted it .

[cataway]

http://i44.photobucket.com/albums/f9/cataway/671605186_559664-1-1.jpg

[Pack]

I'm guessing the Pilot Jet has something to do with the "Pilot Screw"? lol

I have a YFZ, so it's obviously completely different. Any help on how to change/where they're at/whatever, will be greatly appreciated.

Do you have to adjust your needle on these models?

Or is it just fuel screw, main, and pilot jet?

[cataway]

Originally posted by Pack
I'm guessing the Pilot Jet has something to do with the "Pilot Screw"? lol

I have a YFZ, so it's obviously completely different. Any help on how to change/where they're at/whatever, will be greatly appreciated.

Do you have to adjust your needle on these models?

Or is it just fuel screw, main, and pilot jet?
yes the YFZ carb is different but still is does have the same parts,and all basically in the same place.

the needle on the BSR carb does not come with clip spaces yet washers can be added to make some adjustment ,a after market needles are available.

the YFZ carb is not any more difficult to work with yet it has far more adjustments to tune in than the BSR carb, the AP timing needs to be right ,the amount of squirt needs to be right and there is a leak jet in some fcr carb models, there are different fuel pump coveres different needles and mods that can be done
to improve perfomence

[cataway]

http://www.squadpage.com/pandora/Professor%20RedBeard450%20How-To%20AP%20Mod.pdf

http://www.thumperfaq.com/jetting.htm

[Pack]

Ok, how do you specifically change the pilot and main jet, along with adjusting the fuel screw?

[cataway]

ahhhhhhh ...... if you have never changed jets before i'm going to suggest you remove the carb from the quad, reason being the bowl screws can be very difficult to get out and the soft plug may have to be removed .
drilling a hole in the soft plug to get it out would or could be very difficult with it still on the quad.

on the side of the carb is a cover plate held on with 3 screws ,you ether take them out to get to the cable off the wheel or unhook the cable at the thumb throttle and pull the cable out along with the carb, after you get the screws out go to a store and get 7 allen head screws , trust me if you dont do this then the next time you work on the carb you will wished you had.

if you do get the 3 screws out of the plate there is a rather smallish keeper on the cable ''do not loose it '' its on the end of the cable holding the cable into the wheel. its a pain in the butt to work with .deal with it !

remove & replace the jets you want to try and put it all back together.

the fuel screw should be turned in just till it touches the bottom of the hole , please count the number of turns it takes to bottom the screw and replace to the same number of turns out from the bottom when replacing it.

good luck with getting the screws out , i will all most guarantee you'll mess them up.

[airmobile101]

Originally posted by Pack
Ok, how do you specifically change the pilot and main jet, along with adjusting the fuel screw?
If your interested, Im 35 miles south of St.Louis, I can help yea if you dont get it done.

[Pack]

I appreciate it, but I'm about 3 1/2 hours from Springfield. I just need a walkthrough or something.