Big bore question

Hey guys with the winter approaching I'm planning what I'm going to do to my bike.

I'm thinking about putting on a big bore kit either a 270 or a 290 on my 09 kx250f, just have some questions.

---First is unrelated to big bore. My bike has 127 hrs on it and probably won't reach 175 by next winter because I have a practice bike. is it safe to run the bottom end until next winter? I've heard they can last 150-200hrs??

---Second is if I don't need a bottom end til end of 2014 then I'm looking to get a big bore kit. If I get a 270 or 290 kit will my other engine parts wear more quickly??

---Third is I'm looking to increase low to mid because I race a lot of local supercross and obviously u barely ever run the limiter in SX so Im thinking a big bore will really make my kx amazing for SX, so my question is the cheaper 270 do the trick or dish out for that Athena 290? Ill be putting aftermarket exhaust on so that may influence the answer? And I don't want to do cam or valve work either

Also if u think big bore isn't the way to go tell me I'm looking to move up to B and to compensate for skill and speed I'm trying to get something very easy to ride

running a bbk will put added stress on your crank - not saying your crank will let go but it could. - I have a 270 kit and like it but put in a new crank assembly - and honestly all the motor mods in the world wont really make a difference on the track you you can take the top running guys and put them on stock bikes and they will prob still place the same.

running a bbk will put added stress on your crank - not saying your crank will let go but it could. - I have a 270 kit and like it but put in a new crank assembly - and honestly all the motor mods in the world wont really make a difference on the track you you can take the top running guys and put them on stock bikes and they will prob still place the same.

When do u recommend changing out the crank assembly?? because like I said I have another bike I got this year (2 smoker!!!!) and if I could stretch it to next year it'd be much better, because my 125 is used and needs to be gone through this year..

And I understand the motor mod thing, I don't expect to run with top guys in my class at all, Im just looking for something wicked easy to ride, to help bring my confidence up and make my bike feel perfect, because there's no better feeling than riding an amazing bike. Ive always considered getting a 450 but never actually looked into buying one, and with the 250f being lighter and not a fire breathing monster I'd rather just add some more power down low and some to the mid

If I was rich I think I'd go out and get a 350sxf I'm really just looking for something in between 250 and 450

Thanks for the response!

think you would be better off with a pipe and a cam for bottom end BBK kind of brings power up everywhere..... and cranks can go at any time you can at least replace the piston and while your there measure your connecting rod play per the manual

Yea probably a cheaper route also, and then ill go play around with gearing.

And as for replacing the piston I'll do that, I don't like having a piston in there over 50 hours, it currently has 25 hrs and actually what sparked this whole big bore idea is according to everyone who touches the kickstart my bike has low compression, although its always been easy starting and ran great. I was like maybe it's time for a new cylinder?? then I saw the BBKs and looked into them

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