400EX Mods??

[ride red]

I have a 2000 400EX with a cam, piston, and rev box on it. I have a Yoshi slip on, on it now but I want to change to a full system and I think I'm gonna go with the Curtis Sparks X-6, is this a good choice? Also for someone that has never jetted a quad before is it very hard to do because I would say I will have to rejet when I put the full system on, even though it's already jetted. I don't have anything done to the airbox either, by putting vents in the top is that good to do or should I just run without it on it? Any help would be appreciated!!!!!

No, re-jetting is not difficult at all. The directions with the kit are pretty good. If you have any kind of mechanical ability at all, you should be able to do it without any problems.

i would go with the x-4 since you haven't done a big bore

[kabd69667]

You can go w/ either one. Both are great. if i was you i would get the x-6 because if you decide to go w/ a 440 or 416, if you don't already have one, you have the pipe to go w/ it. The x 6 also gives more top end than the x 4 on a basically stock bike, but the x 4 gives better bottom end

running a big bore pipe on a stock bore will kill the bottom end power

[kabd69667]

well it depends on what bore his piston is

[ride red]

I have a White Brothers cam and rev box on it with a JE 11:1 piston in it. I never thought about it slowing me down. Should I go with the X-4 or X-6 or is there another pipe that would better to buy?

[kabd69667]

Is it a stock bore piston or is it .80 over or .120 or what??? thats what we need to know

[ride red]

Yeah it's not bored out just stock bore piston but if I would decide to bore it out later and I would go with the X-4 would I have to change pipes again? It has alot of bottom end right now.

[kabd69667]

You wouldn't have to change, you would just get more power out of the x 6 if you bored it

[400exJOE]

IF HE'S WILLING TO DISH OUT $500+ ON AN EXHAUST SYSTEM WHEN HE ALREADY AS A FINE ONE, WHY NOT SPEND TO MONEY ON A NEW CARB? FCR OR EDELBROCK OR LECTRON. THAT WOULD MAKE A HUGE DIFFERENCE.

[Dave400ex]

When I emailed Sparks about his pipe I told him that I had a stock motor, but some day I wanted to do motor mods. He told me to just get the X-6. On his site it now says that they found out that the X-6 works just as good on a stock motor as on a modified motor. I would get the X-6. Getting a different Carb isn`t a bad idea either. I would get a FCR carb if you did that.

[ride red]

I never really thought about going with a different carb. Would that make more of a difference than putting a full system pipe on it? I thought maybe with all the comprssion my 400EX had now that it would be better to go with the full system so my headpipe is bigger than the stock one or wont this hurt anything?

[400exJOE]

I dont think you should buy a full exhaust and heres why. On a 400ex, the stock headers work fine. Some race quads even use the stock ones even on 440s. I think headers are only necessary on a big bore 400ex. A yoshi slip-on should make a big difference over stock, but between that and a full system, you probably wouldn't notice a big difference. I saw a dyno that showed that an FMF powerbomb gives a 0.2hp increase. That shows how little you gain. It was in Dirtwheels. A carb will add probably around 5hp. In the Jan. Atv action, there is a carb shootout. I havent seen it yet but i guess the winner is the Kehin FCR. Go for the carb.;)

I just bought the Curtis Sparks X-6 pipe. My motor is all stock, except the CDI. I promise you won't go wrong with buying the X-6. You can gain it back by getting the timing advancement key for $15.00.

[ride red]

Thanks for all your help so far on this subject. I'm not sure whether to go with the carb or curtis sparks pipe know. I've heard alot of goodthings about the Kehin FCR Carb. Would this be the best one to go with or is there another one that would be better? I'm still not sure what to do if anyone else has an opinion on the pipe or the carb please let me know. I do alot of drag racing and am thinking about runing mx also if I can get the nerve to do that so I want the best set up as possible espically when I drag race.

It's an excellent carb. But there is an alternative solution. Curtis Sparks Racing will bore your stock carb for about $175.00. I plan on having mine done, and save the extra money for other mods. Something to think about.

[400exJOE]

do the carb! The pipe you have is a very good one. You will notice a much greater preformance gain with a carb. FCRs are very good. Edelbrock should also be good along with Lectron. In the ATV Action Jan. 01 there is a carb shootout for the 400. If anyone reads it, let me know the results. Thanks