Big Bore y? n?

[400exracing]

i have a 2001 400ex i was wondering if it will take away the life of the engine? What is the more reliable big bore kit? 408, 416 426, 440 who sells the best kit(comes with all the parts needed)

[desertrats]

yes, it will take away the life of your engine, depending on bore size. the bigger the bore the less reliability. as far as the best kit, that is all personal preference, IMO. I like ct racing, and duncan is pretty good too. but it would be a lot cheaper to buy a 440 kit from say wiseco, pro-x, someone like that, and then just send it off to get bored, ported and polished and the heads shaved, then buy your own pipe setup for it. If you buy a kit get a 440 kit, because you are losing reliability anyway and you will still be pretty reliable with the 440 and that is also the most powerful kit. If you do decide to get a kit for it, I would look into a bigger oil cooler, deserttoyzatv makes an oil cooler that is 40% bigger than stock and mounts in the same place as the stock one. Do everything you can afford to to keep your quad cooler. Heat is the enemy. A bigger oil tank might be a good idea too, not sure how much cooler it will keep it but it should cool it down some, UM Performance is a good company for the oul tank, but there are others out there id you prefer someone else. Air Scoops are a good idea too, not a whole heap of cooling power but it will still make a noticable difference. Now, you dont have to get all the stuff mentioned to keep it cool, you can still run a 440 kit with out the stuff I mentioned but if you can afford that stuff or even some of it than get it because you will have much more reliability that way. Also to get the most power out of your 440 kit, get a new cam for it, if the kit doesnt come with one, stage 3 will improve all around power, stage 2 is mid to top end, and stage one is low to mid, getting a new cam is all personal preference IMO. Also think about a new carb or take the choke out assembly out of the stock carb (dont worry you can still start in cold weather), just put a bigger pilot jet on so that you can start easy in cold weather. Just pupm the throttle 2-3 times and she will fire right up if you have a bigger pilot jet in. Well thats all I can htink of at the moment. If I think of anything I will post on here. Man I wrote a lot, lol :eek2:

[RiderTRX400ex]

the 416 kit with a JE 10.8:1 piston is really popular

[wheeltrax]

I have a 440 wiseco in my 400 and love it. I have yet to have any problems what so ever. It is a torque monster. I would recommend it to anyone.