Thinking aboout a big bore for a 250 2 smoker.

[eprovenzano]

Recently my 17 year old son son took over my KX250 2 smoker. His YZ125 just doesn't have the arse (5"10" 225-230 lbs) to get him through our tight trails. He tried my two fiddy, and said its mine now... :yikes: He likes the way I set up the KX with, gearing changes, and a flywheel weight. So I am going to sell the 125, and get me another two fiddy 2 smoker.

I was tinkering with the idea of getting something that needs a major engine overhaul. When I look for a new bike, I'll probably look at the 99-01 years (its all about the lack of money). If I'm going to rebuild one, I may as well build it to my specs... I was thinking of going with a big bore. I was wondering what's included with the big bore kits. Do I need to have the cases machined to accept the larger bore, does it require a different crank, etc... I'm also wondering about the durability after its been reworked. I'd like to do the rebuild myself, that way I would know exactly whats been done to the bike.

Any thoughts would be appreciated.

 

[splatt]

What comes with a big bore kit all depends on the bike model and how big. My YZ250 has a 265 kit that came with a piston and rings and a gasket kit. All the machine work was on the cylinder itself as no mods to the the case were required. If you go ahead with this I along with many others on this site recommend Eric Gorr.

Steve

 

[robwbright]

Eric will do an all inclusive kit. If the cases need worked on, you can send him the whole motor and he will do the bore, replate, port, head work, case work and send you back a completely re-assembled motor.

I haven't really noticed any wear difference on my RM144, but I only got about half a season in before breaking my wrist.

Try running a search on here for "265" and "310" - two of the overbore sizes.

Here's a link to get you started:

http://www.dirtrider.net/forums3/printthread.php?t=60151&pp=40