Got a few questions...

[08Honda400EX]

I just ordered some new keihin jets. I hear that quads come stock a little lean, which for me is a #148 main jet, so I bought a #152. I also ordered a #42 pilot jet, which I hear will ease cold starts and make it where you don't even need the choke (which I have considered removing for better airflow but that's another day). Stock pilot jet was a #38. Am I on the right track? Also keep in mind I've never even taken apart a carb before so I could use some tips and advice.

One last thing. I ordered a 13 tooth front sprocket. Stock gearing is 14/39 on 20" tires. I know this will improve low end grunt at the loss of high end speed. I figure this would be better for trail riding, but I want to know if it will also make slow riding easier, like when riding with my wife on her 250 utility? Also I know it's reccommended but must I change both sprockets and the chain at the same time or is it ok to swap just the front sprocket? Not sure how hard this install is either, I figure I'll have to remove the chain but not sure how?

[patches206]

The jets are easy to change, take the carb off, remove the fuel bowl and there right their.  If your going bigger on the jets what about the exhaust, you will need to open it up.   I run a DS650 the stock jet was a main 165 and pilot 40.   I went to a 185 and 42.5 pilot, but I also replaced the stock exhaust with an HMF pipe.  I still need that choke when its gets cold during the winter.  You need to open your air box up as well. More fuel means you will need more air. I leave my air box lid off, with a K&N filter and a pre-filter its worth the extra bucks for that pre filter. You may also have to do a trial and error to find a jet combo which works.  I was lucky I got mine on the first shot with some help off the internet, Good luck.

Oh the 13 tooth should work well.

[svtbolt04]

Removing the choke wont show you ANY noticeable gains.

Also, by removing the choke, you are taking away the bikes ability to properly warm up. Not a good idea.

Gearing

Removing and replacing one or the other just means they will wear unevenly. That is why it is recommended. A newer sprocket might bite harder with more leverage, putting more stress on the existing one (in theory) but it also comes down to how much do you maintain your quad. Do you pre-ride check it all the time? I know I don't all the time, but piece of mind is always there with new components.. thats why you jump on it and say it runs...it runs, and go. As for trail riding, lowering one tooth is going to make some change to the bottom end. It will make the bike deliver torque in a new way. Might make the front end come up a little easier than now, but top end wise, you may only lose 2-5mph.

Invest into a K&N outerwear or a quality foam filter if you decide to run your airbox with the lid off. I do recommend taking it off if you are changing all of these other things.

[mrbones]

Yes, it sounds like you are on track. I remember doing all those same mods when I had my 400ex. Removing the choke is fine. The idea there is to remove a center obstruction that runs right through the middle of the intake side of the carb and increase flow. Unless you want to ride when it's colder than 50 degrees, the larger pilot jet compensates for it and won't cause any problems. Is it worth it? Probably not by the seat of your pants. You'll have to keep an eye on the rubber plug that you use to cover up the hole left behind when removing the choke. It could fall off or crack over time. In retrospect, I think it's better to just leave it alone.

I also did the same gear change. Yes is will make riding slower easier at a slightly higher RPM. It's better for trail riding.

I used a White Brothers pipe when I did mine. It had more power, but it was too loud. As I look back on it all, I enjoyed my 400ex the most when it was in stock form (except the front shocks and front sprocket). It always worked the same every ride with no problems.

[08Honda400EX]

Got the choke idea here: http://www.atvriders.com/articles/choke400ex.html

I currently run a K&N with prefilter, but might soon upgrade to the Pro flow intake, basically the same thing but clamp on style.  I use the stock pipe and I'm hesitant about putting anything aftermarket on it because I don't want it super loud.

Thank you for the responces.  Also looking for a set of stock Honda 450r shock to upgrade mine too.

[eldiablo64]

I don't know how the muffler on the 400 is but on some you can remove the baffle and it won't be all that loud.but you should still use the spark arrester.