Power up kits for the 400ex

[QuadJunkies]

I have a 2002 400ex and Im wanting to get more power and speed out of it,...what power kit is the best to go with for the $$$?416,426,440...Is a rev kit involved???I need all the ins and outs on a full kit and what brands are best..Basically all the info you can give me... the better..Thanks

[Ex'r Marlin]

Kit usually comes with just the piston, piston rings, piston clips, new head gasket, and instructions.

Some riders recommend getting a cam along with your order for two reasons... More performance, and because you are already going into your engine.

You still need to ask yourself some questions, like wanting to continue running "pump" gas or if you get a high compression piston, you may need to start running "race" gas that may not be at a local gas station.

For the money... Due to your machine being a 2002, the best kit to me is the stock bore piston with a higer compression piston. This way you would not have to spend money on boring out your cylinder, but this may not give you the "power" and "speed" you are looking for.

Note: Some performance kit packages may come with a new CDI box. (Like TC Racing for example). The performance kits can include, and not limited to, new exhaust, cam, piston, hardened rockers, titanium valve springs, port and polish, boring of cylinder, gaskets, CDI box, Angle job. This obviously can get into the thousands of dollars.

Good luck shopping!:)

[QuadJunkies]

Thanks for your reply..I forgot to mention,pricing,(thats a HUGE part )Ive heard a huge range from 300.00-4000.00 this is where im a little confused...Why such a big range in pricing.Is ther is BIg difference between the 416,426 or the 440 in performance?

[Dave400ex]

Well there is a big Price change because there is many different ways to do each Kit. You could build a Marcum`s 416 for around $500, but TC`s 416 Motor is $1,500 because it has more Stuff. Heck Sparks 416 is $3,000 I think. There are many different things you can do with each kit. Go to www.sparksracing.com and then check out some other 416 kits and you will know what I`m talking about.

[QuadJunkies]

Ok...So besides Sparks racing..Where else do I go to get info and prices on power kits,Is there a big difference between 416,426,440..Sorry ..new to all of this.If I was to try doing it myself,how diffiult is it to do?Im not going with anything too extreme,because $$$ is an issue.Im not going to spend more than 1000.00 on it all

[Ex'r Marlin]

Originally posted by QuadJunkies
Im not going with anything too extreme,because $$$ is an issue.Im not going to spend more than 1000.00 on it all What kind of riding do you want the speed and power for? For the choices you have listed, they will require some sort of machine work. The 440 kit comes with a sleeve that needs to replace the existing sleeve in the engine. All the other kits require a machinist to bore the cylinder out for the diameter piston you chose. My recommendation is to call some of the places we stated and ask their advise as to what modifications to go with... They will ask you what kind of riding you do, and they will be able to quote you a price, or you can tell them your limit.:cool:

You asked the question if there is a big difference between each of the sizes.... I don't know first hand, but I do now that going from stock to a 416 10.8 to 1 compression piston made a very noticeable difference.:cool:

As for these kits being something that you can do.... If you are mechanically inclined, and have the tools to do it... then I think that would be in your favor... Otherwise, I would recommend putting it in the hands of someone knowledgeable of what is all involved.... I did!

(Sounds to me that for $1000, you will notice a big difference in both speed and power.... But you still need to decide if you are going to use pump gas or not to dictate your compression, which will make an impact of your goal).

[TravEX]

i'm glad quadjunkies started this thread, cause i have been thinking about the same thing for my 02 400,,,if i go with a stock bore higher compression piston and a cam (what brands and type of cam do ya'll recommend), what is the highest compression you can use on 93 octane pump gas?

quadjunkie, i think what they mean about staying with the stock bore on the piston on a new machine is that, don't bore it till you have to, when the motor gets a little older and starts using oil and needed cylinder work, then that is the time to slap a 416 to it :cool:

thanks for all the helpful info so far,,,later

[Tommy 17]

my motor kit is right around 850$ for everything i did and its awesome in power... i did have to buy new rockers though bc my one had a chip in it so figure about 750$ with out it... that was for some guy to do my motor for me becuase i had no idea what i as doin...


i run 10.8:1 compression on my 406 and my friend has 10.8:1 on a 400 bore and they run perfectly fine on 94 octane...


the one thing i will tell u is to buy the more agressive cams they are worth the money i found that out from my friends stock bored xr 400 based machine...

[Ex'r Marlin]

Originally posted by mrtunes
if i go with a stock bore higher compression piston and a cam (what brands and type of cam do ya'll recommend), what is the highest compression you can use on 93 octane pump gas?I have heard great stories of the Honda XR400 drop in cam. You may want to take the recommendation of dealer/engine builder that you are getting the kit from.

Note: There is a new cam out called Hot Cams.... They have a stage 1 and a stage 2, and I hear the stage 2 is very impressive. They too are drop in cams. Like 400ex21 says, I too recommend going with an aggressive cam. Just beware that some aggressive cams require hardened rockers and stiffer valve springs.

From reading the threads and responses of fellow exriders.comr's, the rule of thumb for the 400ex is..... You can run pump gas of 93 or 94 octane with a 10.8 to 1 compression piston. Once you go to a 11 to 1, you may need to either run straight race gas, or do a 50/50 mix. I personally run 94 Sunoco pump gas in my 10.8 to 1 with no problems.... But some riders with the 10.8 to 1 say they notice an improvement when they add race gas to the pump gas. Note: They also make a 10.5 to 1 compression piston, which maybe a wiser choice for some to make sure that the 93 octane pump gas works fine.

Good luck!

[Dave400ex]

I think your Best bet for $1,000 would be a 416 Piston, Cam, and Carb. I know Sparks JE Pistons are $189, I would get their normal Cam that is not a Drop-In so Rockers and Valve Springs are needed. So Cam would be $209, Rockers $200, and Valve Springs $110. With all that you are at $708. Depending on your Compression Ratio you may want a stronger Rod $239, and look real close at a new Cam Chain $100. So now you could be up to $1,047. If you had a limit of $1,500 bucks the only thing left you need is a 39mm FCR Carb and you would have one heck of a built Motor. The Carb would be $450. So your Total would be $1,497. So then it`s just the Labor. That would be a Great motor and worth the extra Cash. TC will also build you a Motor like that and it would be cheaper.

[QuadJunkies]

SO ...approx. how log does a project like this take?It would be a wk. end job and a few hours during the wk after work..You mentioned that TC could do it a little cheaper, were you basing this compared to who? we were going to try and do it ourselves,but if it becomes too complicating , i will have to send it to someone I guess.Any ideas how much for labor??

[QuadJunkies]

oh...And I havent got a reply on how different all the kits are,I mean I know they are all different, butis it worth all that$$ to go with a 416 vs.440 ect.???

oh...And I havent got a reply on how different all the kits are,I mean I know they are all different, butis it worth all that$$ to go with a 416 vs.440 ect.???

To be wiser and get the info a lot faster click below and type in your question, it works like magic.................................

http://209.120.142.52/search.php?s= (http://)


And if you need detailed answers better be posting some detailed questions. How it will be used. what do you expect to get in return for the amnount of money spent. what other mods are you doing. Theres no sense in taking the time ot explain in detail what or why a big bore enginge is going to do for you if you dont have the $$$ or the other mods that will make it work properly.

Just do something even if its wrong:cool:

[Dave400ex]

I was saying TC would be cheaper then Sparks.

[QuadJunkies]

Thanks for all the info..i will be calling a few places this wk. to get prices and help narrow down what i should get.440EX4ME~~As for me needing to be more specific,I didnt think my questions were too dificult ,as you know im new to all of this,or I wouldnt be asking questions and advice from all of you.I am smart enough to know that 1000.00 should get me going well,i just want to make sure what I get I will not regret later...

[QuadJunkies]

Warrior Man~~ I was wondering ,Do you have phone numbers for TC and Sparks? I think I used to have TC but I cant find it.Thanks again :)

[Dave400ex]

TC 814-723-3514
Sparks 661-872-4343

440EX4ME~~As for me needing to be more specific,I didnt think my questions were too dificult ,as you know im new to all of this,or I wouldnt be asking questions and advice from all of you.I am smart enough to know that 1000.00 should get me going well,i just want to make sure what I get I will not regret later...

Well this is the condensed version since the server keeps shutting down my browser every damn time I submit it.

I am not bustin on you here but trying to help you out. There are some great old threads on the info your looking for. I wouldnt suggest it if it wasnt true. If you even slightly thinking of a 440 better search out "have you decked the cylinder" and look into the mickey dunlap Q&A tech articles. This stuff is will answer (and create) most of the tuff questions and even some you dont know you have yet.

There are even some great threads on cams and the 416 v/s 440 thing as well. So just go do it and you wont regret it.

Problem is everyone here has diff opinions and though I am not the one to say who's is right or not they all cant be right, so do your home work and save yourself a lot of $$$ and headaches.

The reason I had asked you for more spefics is that it would get you better answers.

If your thinking of just giving your quad a better punch and making it more fun to ride you will need diff things than if you are looking for it to be a competitive racer.

A $1000.00 is a lot of money (well not really but it aint fifty bucks either) but its also going to dissapear fast if you need a lot of mods. Is your quad currently stock? Or do you have a silencer and intake allready? This stuff makes a diff in how things will work and how fast the cash will disapear..

Some suggestions. You will get the most bang for your buck by going with a high comp piston, cam, silencer and intake. You will not think its the same quad with just this stuff, it makes that much of a difference.

If your able to do the work yourself you will save a bundle of cash, but if your not and try it anyhow it will end up being more than if you just had it done in the first place.

An example of how to save a few bucks, well a lot of $$$. Warriorman is normally spot on with prices and look at this:


I think your Best bet for $1,000 would be a 416 Piston, Cam, and Carb. I know Sparks JE Pistons are $189, I would get their normal Cam that is not a Drop-In so Rockers and Valve Springs are needed. So Cam would be $209, Rockers $200, and Valve Springs $110. With all that you are at $708. Depending on your Compression Ratio you may want a stronger Rod $239, and look real close at a new Cam Chain $100. So now you could be up to $1,047. If you had a limit of $1,500 bucks the only thing left you need is a 39mm FCR Carb and you would have one heck of a built Motor. The Carb would be $450. So your Total would be $1,497. So then it`s just the Labor.

Lets look at this if you purchased this stuff from say the quad shop or who ever. J&E piston kit $110.00 - hot cam $130.00 - gaskets $40.00 total= $280.00 you save $1217.00. Now this is not the same set up but driver ability would be more an issue than the difference in power between the two set ups. You would need to add some $$ for machine work around 30.00 for a cleanup crosshatch of the cyl, about 60.00 to bore for a 416 or 425 etc. around 140.00 to install the sleeve for the 440 (this varies wildly so shop it) If you run the hot cams they claim its a drop in so no need for the extra 300.00+ for rockers and springs. Cam chain is more of a maintenence item to me and I would not change it unless it was worn/streched etc. No matter how you add it up if your able to do the work yourself you could be into stk bore to a 426 (11:1) with a cam for under 400.00 with machine work.

I have heard good and bad things about the various carbs available but I myself am waiting for some "proof" that the stocker is leaning out before I drop the 500.00 into a carb.

Hope that helps and let us know which way your leaning towards.

[Dave400ex]

440EX4me is right. That setup with the Piston and Cam would be awesome. For the money you are saving the power increase won`t drop as much as the price will. Go for it.

[QuadJunkies]

Ok...Ill definately check into this..THis gives me more to go on Thank you 400EX4ME and Warriorman..Ill let you know what I get :)