So I'm riding to work today in the right-hand lane about to switch to the left lane to make a turn. I'm going about 58-60 in a 55 zone. This car comes up behind me in the left lane going about 80 mph. I tried to accelerate so I could switch lanes and make the turn but in the end just couldn't make it and I had to slow waay down (dangerous with cars behind me in right lane) and let him pass before getting over in left lane to turn.

I've got the powerbomb header and q4 exhaust that the previous owner had the dealership install. Is there one thing in particular I should look at to get more acceleration at that speed? Nothing short of a big bore kit or would that even matter?

Edit: klx250sf 2009

 

13 tooth front sprocket, puts her right in the sweet spot at 6th gear 60mph, full throttle gets to 80 pretty quick (no hill of course)

 

one word... nitrous

 

Too much to ask form a 250, probabaly even a 350 for that matter as these small singles aren't sport bikes.

 

I totally agree.
Some KLXers will claim they can cruise all day long at 85mph. Perhaps they live below sea level, or they just ended up with a much stronger bike from the factory, or they've never been on a bigger bike to compare it to, but mine really didn't excel at speeds over 100kmh (60mph).

Ultimately the anemic highway capability was the deal-breaker for me and the reason I sold the little KLX. Though I must say that around town and on trails the KLX was unbeatable!!!

 

I have to agree-the best GPS verified level speed i've seen is about 80 mph. When I ride the KLX on the street I have to keep reminding myself which bike I'm on when it comes to traffic. What would be an effortless pass on my other bikes had damn well better be thought out on the little kawi. The 351 kit added quite a bit of top-end punch but it's not a rocket. As Cytocis said, this bikes forte is on the trail, not the street.

 

butchersong: I'm not sure a bigger bike would have helped you. What did work was your response to a bad situation. Our KLX250's have weaknesses and strengths. This kind of freeway excitement is more common than I like. I just keep working on the bike's shortcomings. It's getting there. Stay safe, please.

 

One of the limiting factors in WOT on the KLX is the carb. The OEM carb just doesn't limit throttle response. It limits top end also. While my '06 model only has the OEM KLX300 kit...292cc actually...the 36mm pumper carb really pumped up the throttle response. But it did something else. It awakened the top end also. As long as jetting, exhaust, and intake are capable of maximum performance, the 2 extra mm of carb opening coupled with the no obstruction design of the Mikuni's carb throat "can" yield better performance throughout the rpm range and throttle position. I have a full Muzzy exhaust and an airbox with lid mods and backfire screen removed. Top end and the response all the way to wide open throttle improved dramatically. When you look down the throat of the OEM carb and a modern, flat slide, pumper carb, you see why performance can be improved at all levels. The throttle plate and shaft on the OEM carb is always there, and of course the slide itself moves independently of what the throttle linkage is doing. This is not to say that the OEM carb is a total piece of junk. However, it doesn't flow with the efficiency of the pumper carb. The 36 pumper not only yields a larger throttle bore, it also has a totally smooth, open avenue from the airbox to the engine. When jetted properly, the 36mm pumper, or even the 34mm pumper, is a superior fuel delivery device for the KLX.

I was a bit of a nay-sayer on the pumper carb conversion. I didn't really think it would have that much of a beneficial impact on the KLX. I only regret I didn't do this mod sooner. Improve the exhaust, air intake, and carb, and you get a dramatically improved performance...period. I already had the exhaust and intake mods, so I was really able to tell how much improvement the pumper carb made.

 

Do you think the 36 is a large jump from a 34? Meaning, does it REALLY improve from the 2mm of bore?

 

Without flow bench testing, I tend to think the design of the carb throat...absolutely nothing in the path of incoming air at WOT...is more important than the 2mm increase in bore. That said, when you have the throttle/slide completely out of the way on WOT, as long as you have improved exhaust and intake flow, how can 2mm of additional bore hurt in this case? Yes...one can overcarburate. I've done on it bikes in the past. However, the KLX seems more than capable of using that extra 2mm of intake size without issue. My fuel mileage seems to verify that. The 36mm carb is cheaper and easier to install as a side bonus. The jetting work that was done by some former members made the carb install just about painless.