My 2007 KLX-250S needs a good thorough service so, I'm debating doing a 351cc upgrade along with a possible carb swap. Having my shoulder rebuilt makes this type of service really difficult for me so, I'm wondering if I can find an under-employed tech that can fix me up without breaking the bank. What sort of cost should I be looking at? I'm not looking for anything crazy but, I want more grunt (torque) for lower RPM running while also being able to breathe a bit more fire on the top end for hill climbs or fast highway sprints between trails. I should note that I also do a lot of ~45MPH rural road cruising so, a reasonable gas range and a less than obnoxious exhaust note are desired. Currently, it has the 'free mods' and a KLX-300 exhaust with stock 250cc jug.

I'm in East Texas FWIW but, Dallas, Shreveport, OKC are all easy drives for me with family and friends in those areas. I don't want some ham-fisted storefront mechanic who will bugger up screws and bolts like some of the guys I have used in the past for warranty related service.

TIA,
Sid

 

I don't have a mech for you, but your 300 muffler is too loud? ... I'm with u, I run a stock 250 exhaust, it is loud enough!!!!! .... I like to sneak up on wild life and other critters.
I would just put a slide carb on it and give it a go for more torque, you can always put the 351 in later. ... drop the countershaft sprocket to a 13.

 

I'm already running a larger rear sprocket with the free mods. The KLX-300 muffler isn't really louder to my ear than the stock one but, it breathes better so my little 250cc engine runs a bit better and is jetted for the better airbox and exhaust flow.

I don't really want it geared any lower for street use so, upping the power is what I really need. A full exhaust swap by itself doesn't seem to be worth the expense compared to what I would get with a 351cc upgrade. Plus, I don't want to go to something that will hurt the ears of anyone around me so, more torque at modest revs with a quiet'ish exhaust is what I'm really after. I don't need exhaust stealth mode nor a fire breathing high revving option either so, a subdued high torque 351cc engine seems to be a good option for me.

I have been considering a DRZ-400S though as a compromise. I'm not sure I will like the additional weight and the higher seat height though.

 

Based on my experience, displacement makes the biggest impact on performance.
The 351 produces quite a bit more low-end torque than the 250, so plonking over obstacles is easier.
The stock CVK carb works well after dialing the jetting, but a pumper carb also helps with throttle response.
The exhaust is more sound and weight than power gains.

 

With stock 2007 exhaust, my KLX-250S seemed pretty stuffed up and restricted. The KLX-300 retrofit didn't really affect weight but, in my case it did help open things up more. I did the free mods on a stock motorcycle and it helped some but, not a whole lot. When I put the reclaimed KLX-300 exhaust on, it ran better for me once jetted correctly. I think less back-pressure on the exhaust helped the carb and airbox get a bit more fresh air into the system for a better fuel burn. Nothing earth shattering but, it did help in the low and mid-range engine performance which is where I liked to run the engine for most of my travels.

 

As I said, I'd just put a pumper carb on it and give it a go.
If I was going to update to another bike, I would get a new Honda 250. I don't see any reason to go the DR400 route with their wt. & suspension which would have to be completely redone.

 

Sid,

I'm just curious if your already completed free mods include the MCM cam timing adjustment?

 

No, I haven't updated the cam timing.

 

Yeah, me neither. But if you're after low to mid grunt, I understand that's a good free option to pursue. I acknowledge that, in your shoulder rebuild condition, it likely will be a bit of a chore.