Newb here, just had a question. I bought a 2005 400ex and it came with a pro circuit T-4 pipe and is not jetted according to the old owner. Do I need to rejet it? once it is warmed up seems to run fine but, seems to be really cold blooded. Also the tip of the pipe is gone from him doing wheelies just a plate now. My old z400 would always start right away and stay idling. Can anyone help!
Thanks

400ex

 

Better do a plug check. Honda jets lean at the factory.......you add a pipe without a rejet and it will be even worse. If you are running lean, you can severely damage your engine!

 

yes you will want to rejet and put the endcap back on or order one for the procircuit

 

i've got a 2002 400ex and i also have the pro circut t-4 pipe, i bought the k&n filter, jets and pipe all at the same time with 20 hrs on the quad. i put the filter and the pipe on and took it for a quick spin to see what kind of inprovements it made, a differenct but barely. i brought it back after about 10 min, she was running way lean by the looks of the spark plug, i rejeted it, can't rember which one it was, but then took it back out. WOW the jet made a huge diff! it runs a little rich right now. my 400 has always been cold blooded sence i had its first hr on the eng. i havn't seen one that isn't. also a reason for it being a hard start is your valve lash is off, i know after i adjusted mine for the first time it would run much better at lower rpms when the eng wasn't quite warmed up. well best of luck to ya. keep us posted on how things go. bowz

 

thank you all for you helpful replies, I think I will rejet before I ride it at all, the previous owner didn't ride it much and I am hoping since the airfilter had never been cleaned not much air was getting through to make it run rich, very dirty, if that makes any sence?when I checked the plug it seemed to be black, then I cleaned the filter and changed the plug to an NGK and took her for a spin running the gears at top speed, shutting it off after pulling the clutch in and stopping that way, checked the plug and the plug is light white greyish, so now seems to be running lean. A guy at the shop recommended a 150 main and 40 pilot 2 up is a great start he said. well see thanks again!

 

ok some of the things you said don't make sense....

"I am hoping since the air filter had never been cleaned not much air was getting through to make it run to lean, very dirty"
that would make it rich. so then your next statement

" also did check the plug and it seems to be black"
would be a sign of a rich mixture. not lean. i would ride with the clean air filter and see how your plug looks after say and hour or two. before i re jet it. and fix your end cap.

HR

 

Sorry meant to say I put a new plug in then checked it and it was white after I cleaned the air filter. so yes it seemed to run rich at first, assuming because the filter was dirty not letting much air in. Now that the filter is clean air flow is making it lean. Whats the effect of not getting a end cap on there?

 

well I would def clean the airfilter making sure none of that dirt will get into your engine...with a plug having a white tip on the electrode that means you are running a lean condition and if you did decide to ride it then that could cause harm to your engine that could be fatal...go buy a good jet kit with a needle and rejet and then you won't have any problems make sure you buy a few extra main jets in different sizes just incase you need them for something at a later date

 

for your end cap, in 02 when i bought my t-4 u could get 3 caps, i can't rember what sizes they wher 1 1/4, 1 1/2 and 2in i THINK yeah ha i have no idea now, well i got the biggest one, thinking it was the best and prob the loudest, mostly the loudest "i thought" . the diffrent sizes they said were for giving ya top power at different rpms. as for one not being on there, i know if you dont' have any back pressure in your exhaust (end cap, packing, baffels, or even exhaust itself) you will burn out your valves, but u say you have a plate on it? with a hole cut? i can't see it doing any damage, but i know for sure you can pick up diffrent tips and trade them out, i'll see if i can find them for ya. let us know what happens. bowz

 

http://www.denniskirk.com/jsp/produc...0903&brand=592

there is a quiet tip for your exhaust.

here this one is better, see if this helps

http://procircuit.rideshop.com/catal...Path=5_166_183