pro circuit t4 jetting?

[copracer522]

here is what I have 03 400ex, and I just added a t4 pipe. My question is do I need to change the main jet , and if I do what size should it be? my airbox/filter is stock. I road it for about 5 minutes after installing the pipe, seemed like it pulled alot harder, but I dont want to mess the motor up and wont ride until i get the jet if thats what is needed, also where besides the honda dealer can i get the jets from?

[lars]

where do u live whats your elevation is the carb all stock now with no air box mods and stock airfilter

[copracer522]

I live in jacksonville florida, at sea level and the bike is all stock except pipe

[lars]

heres my experience with the T4 i tried one was to load for me me but my buddies have em i went from a 148 stock main jet up one size 150 or try a 155 one of these should work with stock air box and filter just do a plug check good luck your local honda dealer should hook u up my dealer told me how to jet it and what size to start out with

[Braff1]

500 ft elevation

152 summer

155 winter

plug sandy brown.

[Desert Rat]

The T-4 will make your exhaust flow better not lean you mixture. You probably don't need to do anything. If you add an after market filter and open up your air box or run it without a lid you will be pumping more air and that will lean you system out. That is when you need to go to a larger main jet and possibly change your needle clip setting and/or go to a different taper. Do a plug check and if it is light brown you should be fine. Remember the pilot effects up to 1/4 throttle, the needle from 1/4 to 3/4 and the main the top end. If you go to a K&N filter get their power kit. Has the filter, outer wear, cleaner, oil, dino-jet kit (that they have fully tested and includes several jets and a different taper needle), instruction etc. for around $100. Good deal, especially if you are new to jetting. I run a 440ex with several modes and got a power kit with instructions when I did the engine and air box modes and it worked out great. My new Predator didn't need any jet changes with a new pipe but needed to be bumped up a couple sizes along with some other changes as soon as I put the K&N on it and opened up the air box. Took a lot of trial and error because there weren't any tested kits out yet. The pipe makes a bigger power difference than the filter, airbox and jetting changes will make. Good luck.

[400exInMI]

Originally posted by Desert Rat
The T-4 will make your exhaust flow better not lean you mixture. You probably don't need to do anything.
Actually you’re wrong .......if your exhaust flows more freely, that means less, much less back pressure in the exhaust. The less BP, the more airflow into the combustion chamber....the exhaust will leave the combustion chamber more quickly and more completely.....I changed only my pipe to the slip on, (PC T-4) rode it and my plug was snow white......before the plug changed it was a light to dark brown.....no other mods......Think about it.....

[lars]

how fast is that baby on the speedo jeremy

[400exInMI]

175mph

[cals400ex]

if it is the slip on, i would put the 152 in. you live in florida so it is pretty hot there. however, a 155 would probally work too. also, it WILL run a little better when you rejet a bike. putting a pipe on leans out the A/F ratio. to compensate for the quicker exiting air, you need to increase the fuel a bit. good luck