I just bought a 2010 klx250sf with 3600 miles, 100% stock. I've been reading about mods like full exhaust, opening air flow and jet kit. My question is what effect do these modifications have on gas mileage?

Does anyone have experience with this?

 

It will give you alittle bump at the pump but not much.. If your like me and most of the crew.. Your on the Gas a lot so.. It's all about getting a bump in HP and havin fun..With that said Its kinda a must do.. Let the Mods begin.. Enjoy

 

The answer is actually very simple - do the forum mods like I have and you won't care about fuel mileage - the bike is so much more fun and powerful you'll be hot-rodding it constantly and worrying about speeding tickets. At least that's my experience...

 

I don't mind a little dip in mpg but don't want to destroy it either.

What's the general consensus on the specific brands of mods. I was thinking about exhaust, jet kit.

 

351 kit, mpg raised from 48-52 to 54-57

 

Check out my mods in my signature. Went from ~68 mpg stock to ~58 currently. I'd trade 1/7th reduction in fuel economy for the added fun any day.

 

I was searching on mileage looking to learn and comment. I just finalized on my jetting and a happily making more and smoother power than before but experiencing fuel economy around 70+mpg while commuting in bumper to bumper traffic and 70+ mph blasts. I am surprised. Mileage on my as bought bike with the current exhaust pre-MCM was barely better at 70-75mpg running a DJ132@3N with annoying lean surging. All I have done is learn from KLXSTER and BAM. I was using my current setup at 3N getting low to mid 60s mpg. Eventually I will run BB kits(300 first, then 351, as each reaches it's end of life) and may be back looking for jetting solutions but for now I think my bike is optimized. Wonder how long I will have to wait for the 250 to wear out but not rushing it. Just passed 10K miles.

 

Hop up doesn't always detroy mpg on lean stopped up motorcycles. My stock KLX650 got 50 mpg even after pulling the snorkel and installing a Dial-A-Jet aided power some, filling in for the lean jetting, but didn't really do much for the mpg. I did a Vulcan big bore going to a 102mm piston, a Baja Designs full exhaust, cut the lid a bit more. The bike went to 60 mpg virtually no matter how I rode. We can do back roads all day long running 80, run around town and commuting, or goofing around on dirt/gravel it doesn't really matter, the mpg is consistently between 58-62 mpg.

I haven't checked on the 250 at this point other than a generalization since I'm running a 13/47 gear, but still hit around 50 mpg running stock bore, stock exhaust, KLX300 jetting and Dial-A-Jet, and cams retimed. I have an exhaust laying in the garage, it would be interesting to see what it would do. With the ratty rainy days it's kind of disheartening and non-energizing - aka it sucks.

One key is to run the bike in the range it is built to run. Lugging the engine too low eats gas. We had 1982-87 Honda 4 cylinder Gold Wing riders complaining about bad mpg and poor throttle response. In virtually every case you would find them trying to lug the engine around under 3000 rpm. We had one rider who complained his 1100 would shudder and stumble when he was accelerating... then we found out he was complaining about this happening as he rode across parking lots in fourth gear!

Honda service specifically told us the engine's best range of performance for efficiency was between 3500-4500 rpm, where the most power was generated, not the most horsepower, the most torque - even if it meant downshifting a gear or two.

My friend and I had standard Wings (no bags no fairings) his a 1200 and mine an 1100. We did a trip to Niagra Falls through the two lane roads of Pennsylvania and New York for a lot of it. He and I both got 50 mpg even though a fair amount of fourth gear running was involved. In fact I regularly got 50 mpg with mine.

I don't make any effort to conserve, I just make sure I'm in the sweet zone for power. On the 650 it's between 35j00-4500, the 250 seems to be between 5500-7000. Other than the gliding in traffic, I don't drop under around 5500 when accelerating, plus I will downshift to maintain that sweet spot whether in traffic or out on open running.

One last note, if you look at a dyno chart for an engine - even a general one on-line - you can see that sweet spot. It is where the engine is generating around 80-85% peak torque, the smaller the engine the higher the percentage.. That is where the engine will work the easiest with the least effort, the most efficient range of operation. The broader (flatter) the torque curve the wider the power band.

Hope that helps a bit in riding thought and technique. Lowest rpm doesn't generate the highest mpg, nor does lowest power. Efficient engine performance does. Find where that is then use it.

Why do you worry about the engine wearing out? Everyone had the same attitude when Honda, Nissan, and Toyota came in with 1.5-2.0L (1500-2000cc) car engines. Those with "big durable V-8" think said that - "They're too small, they won't last." I think we know what happened there... That little 250 engine has the same quality design and materials. 10,000 miles is nothing. I've got over 30,000 on the 650 and over 15,000 when I got the 250. I'm not at all concerned with how long either will last.

 

I am more worried the 250 will last TOO long and prevent me from enjoying more displacement with a BB kit, but since I am dialed in with the 250 I will be OK. I have around 76K miles on my 95 Magna and expect the Kaw to be similarly well engineered.

 

I sold Hondas, really liked the 750 Magnas from the 90s, more a standard than a cruiser and more power than any of the V-twins. We only wish Honda had put the VFR crank and cam timing in it. The VFR sounded like a small block Chevy, quite awesome. That and a bit more horsepower from the sport engine parts. Not that it really needed it.

If I do ever go cruiser that bike, even it is a mid-90s bike, it would definitely be in my consideration. A V-4 with mid-set pegs and good ergos - the ticket for fun when the road starts to curve. I don't remember ever reading anything about them dragging any hard parts.

One friend from back in the day, a fellow industrial arts teacher, rode an 86 VFR somewhere around 100,000 miles, got another, but still has the 86 last I knew. some serious touring on that set of wheels. Great design, tough engine.