Big bore kit

[HondaRider250]

I was thinkin about gettin a wiseco 440 kit for my kfx, what do u have to do as far as tuning when u get a big bore kit? ive never installed one. thanks for any help

[400exrider_ed]

Go with a ATHENA kit easy bolt on install. Inlcudes all new cylinder parts as needed. To make a big bore worth the money get some cams and a FCR carb first. The cams and carb will add more power then the big bore alone would.

[HondaRider250]

how big of a carb should i use? and what jetting has anyone used on a 450 kit?

[HondaRider250]

440 kit my bad

[was123]

there are some wisco 440 bolt on kits out there but the athena is good also... and i would do the cams and head but if cash is tight you could wait on the carb you do the head and add cams to a big bore you will feel the diffrence without a carb... and i plan on a 39 or 40mm fcr...someday...

[Defiant1585]

i love my wiseco big bore. only thing i regret is buyin the cams with the kit (ebay special) because now i dont know how much difffrence the big bore made itself. also i think the cams suck to much top end and not enough bottom for tight woods riding. my oppinion get the big bore skipp the cams

[zeus54]

for optimum performance in the woods i use just the intake cam from hotcams,but if its track time they both go in. i have a wiseco kit installed and i think it is a better kit than some of the other kits but i also have an athena 435 kit sitting in a box just in case my 440 decides to crap out on me. i purchased a 41mm fcr from eddie sanders racing the carb is already set up to run with a stock motor i had to increase main jet sizes and needle height adjustment's. before i put the 440 kit in i had just cams with high compression piston it was pretty strong for the woods but not a great track contender with yamadawg's and hyundai's i meen honda's :p so if you can afford the pieces it will turn out awesome

[400exrider_ed]

Just use a FCR 39MM the cheapest way is to grab a used stock YFZ450 carb from ebay. They are very easy to jet and add more power than a big bore would. Plus when you go big bore it would be worthless without the bigger carb and higher cams to feed more air/fuel in and out of the bigger jug. Porting a head on a Z400 is not worth the money you would have to be a Hardcore pro racer or have a monster stroked motor to actually feel any power gains the z's have a pretty well factory head and the valves are already big for a 400. Also if you go big bore and dont use a Athena make sure a good shop sleeves your stock jug, inproper machining is very commen and lead to headgasket headaches, plus a sleeved jug will run much hotter than the Athena's and required a little fatter jetting to help cool it down. I have been messing with these z motor's since they came out and found what's hot and not at my own expense and am looking to help others not have to spend tons to find for themselves what works. I am no brand loyalist or salesmen so I won't feed you a line of bs.

[HondaRider250]

so ur saying i should go athena so i wont have to have my cylinder sleeved and it will run cooler? thanks alot for all the info

[400exrider_ed]

Yes the athena runs cooler and is a new cylinder, and can be bought for about the same price as having a cylinder sleeved. The best price is advantage cycle. BUT BUT I am saying without some good cams and a bigger carb you will be totally disaponted in the power gain from just the big bore alone. The cams and carb are a MUCH bigger power gain. Trust me on this one, I have built these motors both ways first and the cam and carb are the big gain.

[HondaRider250]

thanks a lot for all the info! one last ?, im lookin for more top end power, should i get an intake or exhaust cam, or both? if im lookin for more low end power which should i get?

[was123]

and im sorry but a good port job on a ltz head makes a diffrence..
i installed hotcams,springs and ported my head.with my stock bore and could beat quads with no porting and 434 bore kit...
now i also run the big bore but the porting and cams made a big diffrence in the beginning...

[400exrider_ed]

A port job will only yeild minimal power per dollar spent for what he's looking for. I have a had a few different head configurations and tried them on various engine combos from stock to full on modded motors. It's not worth the kind of money for a z engine, not only by feel also by wheel dyno's. You ported and camed together so the cams are more what you felt. And yes a camed and carbed 400cc is just as fast and sometimes faster in certian power curves than a 434 or 450stroked big bore motor. Thats why I am suggesting that he goes with cams and carbs first. And for the other question yes both hot cams will add more top end compared to a single cam. If you want big top end and dont mind a flatter bottom you could even go with a FCR40 over 39, but the 39 performs better on a stock bore. Also a good QUALITY CDI system like a Dyna Fs or Vortex X-10 will aid the overall performance and boost power where you prefer it by using different timing curves they have programmed in them. But if you go with a CDI add some DRZ-E valve springs to your head to prevent valve floating, they are only 38 bucks new from Suzuki. Also a small mod that is effective and gets more effective when you add more performance parts is to open up your air-flow system from the air box. Get a 400ex 01 year box-to-carb boot and either a Pro-Designs Pro-flow or a CFM Aluminum air box to allow a bigger filter to flow more air. The oem design filter is to restricted and the stock boot is very restrictive.

[400exrider707]

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