I have a 331 with pumper and full exhaust 15/42 gearing. It's not a problem hitting 90mph now but still not a lot of passing power. It's fine for a short rip up the highway but not the right kind of bike for an hour ride. Mpg depends on tires,gearing and terrain, I've gotten anywhere from 8 mpg to 60. Compared to my stock Crf250 there is a definite advantage in going B.B.

 

Personal opinion here, having both a dual sport 650 and street bike - Freeways suck no matter what you're riding. If you enjoy a dual sport you're going to hate a freeway ride even on a Gold Wing.

Sure, comfort is the big difference, but it still sucks.

Fact is going big bore ups your power without upping your weight much if any, where going bigger bike ups both. If you want or need the lighter bike for off roading, go big bore, otherwise go bigger dual sport. My 650 is great for road stuff, but handles me when on the single track. Not good. I really would love to try a 351 KLX, sounds really interesting and I could actually do some single tracking. No KTMs, too much maintenance for my lifestyle... older lazy guy.

If your freeway riding is separate from your dual sport stuff do it right - buy a street bike. That's what I did. I have the Zephyr 550 with a seat twice as wide as the KLX650, definitely more comfortable on the drone.

 

I commute on my SF, I don't need it to be like a sv650 on the freeway, but improvement over the 250 is important, I don't always take freeways, but when I do, I drink...oh wait..I mean I usually do it for 45 minutes.

I like the idea of having an all around bike, I know many say you can't do that, but I'm willing to compromise. Right now it's either buy a 650 for better street manners, or keep a 250 and big bore it because it's cheaper and may satisfy my needs. Oh decisions decisions haha

 

I'd do a DRz400 first, the 650s are way too heavy off road. The DRz will do the job on the road, it is the riders that have problems with the rpm. A friend and I play "joe supermoto" and he would run his DRz400 that he converted supermoto at 80-85 mph all day long, no problem... until he got an SM speedo gear case and found out how fast he was going. Still the bike can do it no problem.

 

The title of your thread is 331 OR 351... If you are considering a big bore kit I currently have a brand new, in the box, never installed Bill Blue 351 kit and TM34 pumper carb for sale... I used the carb for 2 rides before changing to something else. This is absolutely the best bang for the buck if you are looking to add some HP to your KLX... I'll take $600 for the whole kit shipped. You will not beat that price... This would cost over a grand directly from Bill...

 

How much for just the carb.

 

If I split the package up then I need $280 for the just the carb shipped.... This is also a smoking deal considering I gave Bill $400 for it less then 2 months ago!

 

So how much for the big bore?

 

I'm giving a much better deal selling this as a package... If I split it up I want quite a bit more... I need $475 for just the BBK shipped.

 

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