I'm considering one of Eric's overbore kits for my 98 KX250. Looking for recommendations between the 310 and 265 (2mm over). Quite honestly, I'm satisfied with the current power of my 250. To this end, I'm aiming towards the 265 in the pure interest of plating repair. But should I consider the 310? Sounds like it'd be a handful for MX but don't know for sure. Would appreciate any feedback on the pros and cons of these two options.
KX310 or KX265
- Thread starter MXTex
- Start date
I've ridden 250's and my 310 back to back and there's no comparison. Each has there advantages/disadvantages. You know you're riding something different when you're on the 310 and it's probably very similiar to the threads between the KTM 250 and 300. Do a search on those for more related info.
One thing you notice right away is that the 250 feels more like a 125 (after you've hopped off the 310), because it has a distinct powerband and more top end rush than the 310. Plus, at full tilt, it's more manageable than the 310. I would venture to guess that a 265 would be more of everything that the 250 has.
On the 310, the powerband just flat out changes. There's more low end, a lot more midrange, and less top end then the 250. I have the stock gearing on my KX and it pulls each gear very hard. Once I richened up the jetting and retarded the ignition timng, it smoothed out the midrange and gave me more top end, but not as much as a 250. I still have the stock pipe on there, so if I want more top end it'll probably require a pipe change.
Once you adapt you're riding style, however, the 310 is a joy. I find myself going into corners a gear or two higher than a 250 and just feeding the throttle with a slight application of the clutch and carrying good momentum. Although you could be Don Garlits from corner to corner, this motor (much like a mini-open bike) rewards momentum and a workmanlike(ie more sedate) approach.
You've probably seen my other posts on a flywheel weight. I'm thinking of doing this to only enhance the tractability even more.
Tough choice. If you want more of everything your 250 has, I think the 265 with porting is the choice. If you want something totally different, the 310 (which also has porting done to it) is your choice.
One thing you notice right away is that the 250 feels more like a 125 (after you've hopped off the 310), because it has a distinct powerband and more top end rush than the 310. Plus, at full tilt, it's more manageable than the 310. I would venture to guess that a 265 would be more of everything that the 250 has.
On the 310, the powerband just flat out changes. There's more low end, a lot more midrange, and less top end then the 250. I have the stock gearing on my KX and it pulls each gear very hard. Once I richened up the jetting and retarded the ignition timng, it smoothed out the midrange and gave me more top end, but not as much as a 250. I still have the stock pipe on there, so if I want more top end it'll probably require a pipe change.
Once you adapt you're riding style, however, the 310 is a joy. I find myself going into corners a gear or two higher than a 250 and just feeding the throttle with a slight application of the clutch and carrying good momentum. Although you could be Don Garlits from corner to corner, this motor (much like a mini-open bike) rewards momentum and a workmanlike(ie more sedate) approach.
You've probably seen my other posts on a flywheel weight. I'm thinking of doing this to only enhance the tractability even more.
Tough choice. If you want more of everything your 250 has, I think the 265 with porting is the choice. If you want something totally different, the 310 (which also has porting done to it) is your choice.
- Apr 11, 2001
- 559
- 0
I'd have to agree w/Tex. I've got the 267 kit from Eric and I really like it. It's kinda hard to tell the diff. considering that I was off my bike for almost a month and a half. A buddy and I swiched bikes(he's got a '01 YZ250), and he said that mine is deffinately faster. The powerbands are really similar, thou'. The 'band didn't really change much, there's just more of it. I personally thought that there wasn't as much top end as before, but considering what my buddy said and my time off it, I may not be able to accurately tell. It does vibrate more, but not so much as to drive you nuts, but you can tell it's there. The first time I got it on the track, I had a seroius time trying to keep the front end down until I got used to the power. Overall, I'm REALLY happy w/it.
Senior KX Rider
Super Power AssClown
- Nov 9, 1999
- 8,577
- 0
If you are going with an overbore, the 310 is hard to beat. There is more boost everywhere. From off idle to full throttle you will be able to tell a big difference. :cool: :cool:
Keep in mind that if you go with the 310 2mm you have no more capacity
and you cyliender will have to be replaced if worn. I had Eric Gorr do the 265
on my KX and some milling for low to mid power for woods riding, and I'm
very happy with the results. His prices good and quality of work the best
i've seen, just tell him what kind of power you want and you've got it.
and you cyliender will have to be replaced if worn. I had Eric Gorr do the 265
on my KX and some milling for low to mid power for woods riding, and I'm
very happy with the results. His prices good and quality of work the best
i've seen, just tell him what kind of power you want and you've got it.
