Has anyone here "big-bored" their 250?

[mxPro738]

I was wondering if anyone on this forum has turned their CR/YZ/RM/KX 250 into a big bore (for example 275cc or 285cc).

I would like to know the results of that operation? I am an expert level rider and have an '01 CR250 that I am considering doing this to. It is already built and very fast on top, so my goal us to beef up the low end, add some to the mid-range, and just a touch to the top end, thus broadening the powerband. I think anything more might actually make the bike too much to handle on the MX track.

If you have done this, please share you experiences, likes, and dislikes.

Thanks & regards!

 

[reynome]

I just had Gorr do a 275 kit on my 00 cr 250. I have had to do some serious rejetting and cant give a report on the performance yet. I did get the mid and top dialed in a little and I could tell that the mid was like my old 94 but even more powerful! I am trying to get the low end jetted correctly, I didnt have my powervavle adjusted correctly eithor. It was flapping a little at idle and slightly above, I adjusted it for a little tension and it seems to be working much better now. Eric was dead on when he suggested that could be a source of the lack of low end. Everything he did seems top notch, got the cylendar back pretty quick and am looking forward to dialing it in this sat. I will give you a better update after that.

 

[mxPro738]

Thanks 'reynome'. Your offer to follow up is appreciated!

 

[smarttoys]

I had a 275 kit on my 2000 CR250, it was not done by Eric. I really liked it for MX. It had good low end and midrange but it fell flat on top fairly fast. I did some porting changes and head mods and got it working really well. I would recommend it, I personally liked it better than the 265 kit but that works really well too. Whatever you decide on, I would suggest that you have Eric Gorr do the modifications for you. You can tell him what you are looking for in power delivery and he will get it set up fairly close to how you want it and it will save you time and money in the long run.