2002 CR250-Do I port or just go with the Big Bore?

if you like to ride the bike at lower rpms mid-low get the big bore if you like to ride it like a 125 just get the porting

Aloha Tracy, do it...it is worth every penny! :cool:

From what I've gathered, the Mo Betta on a stock bore will fill in the bottom hole and then add a bit of power all over.

The same port job on a 265 bore job will also fill in the bottom end hole and add holy crap power into the top end.

:think: I have an 02 CR250 and sent the cylinder to Eric G for the 265 kit and I know he did some porting. He also cuts the cylinder head to up the compression. When I got it back WOW, :yikes: the thing moves now! Unfortunately it's very high strung and prone to pinging and detonation. Race gas is absolutely mandatory which is a pain for me to find in my rural area. I tried to use octane booster but I don't think that was good enough and blew the thing up in a high speed wash one day. I had him make me a new cylinder head-relieved for the 265 piston but basically stock compression. This seems to be a decent compromise. It's not as strong as with the hi-comp head but a significant improvement over stock and just the slightest bit of detonation running octane booster and it has been staying together. My bike is also set up similar to yours : Doma pipe, V-force reeds, stock silencer, I'm also running taller gears-14/47 so the mid-range power is more important for me.

My ported & raised compression '03 has 'holy crap' power through the midrange, with a healthy improvement on the bottom and improved overrev on top.

Bedell and I run near identical setups including porting, with the sole exception that his '02 was running the stock reeds and Mikuni carb when I rode it. We traded off for a few laps, and it became evident that the power advantage of my '03 was profound (I'd guess 4-5HP through the midrange). It had us scratching our heads. I believe he has since changed out his reeds for the V-force setup (I run Boyesen) and he reports a marked improvement. I'm still somewhat skeptical that reeds and carb alone could account for such a difference, and have wondered if differences in the CDi unit between '02 and '03 could also contribute.

So this is somewhat off-topic, but my point was that there can be considerable variance in the performance of any machine, even identical models with very close setups. Don't underestimate the effect that supporting mods and good jetting can have on the way your ported bike runs.

who makes the 277??? is that a bore and stroker??? if so, i would just stick with the big bore since the strokers are spendy, and can open up a can of worms with ignition pipes, etc etc.